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Rare diseases are particular pathological conditions affecting a limited number of people and few drugs are known to be effective as therapeutic treatment. Gaucher disease, caused by a deficiency of the lysosomal enzyme glucocerebrosidase, belongs to this class of disorders, and it is considered the most common among the Lysosomal Storage Diseases. The two main therapeutic approaches are the Enzyme Replacement Therapy (ERT) and the Substrate Reduction Therapy (SRT). ERT, consisting in replacing the defective enzyme by administering a recombinant enzyme, is effective in alleviating the visceral symptoms, hallmarks of the most common subtype of the disease whereas it has no effects when symptoms involve CNS, since the recombinant protein is unable to significantly cross the Blood Brain Barrier. The SRT strategy involves inhibiting glucosylceramide synthase (GCS), the enzyme responsible for the production of the associated storage molecule. The rational design of new inhibitors of GCS has been hampered by the lack of either the crystal structure of the enzyme or an in-silico model of the active site which could provide important information regarding the interactions of potential inhibitors with the target, but, despite this, interesting results have been obtained and are herein reviewed., (© 2024 Wiley-VCH GmbH.)

Several novel chemical series were identified that modulate glucocerebrosidase (GCase). Compounds from these series are active on glucosylceramide, unlike other known GCase modulators. We obtained GCase crystal structures with two compounds that have distinct chemotypes. Positive allosteric modulators bind to a site on GCase and induce conformational changes, but also induce an equilibrium state between monomer and dimer., (© 2024 Wiley‐VCH GmbH.)

Gaucher disease is a lysosomal storage disorder caused by mutations which destabilize the native folded form of GCase, triggering degradation and ultimately resulting in low enzyme activity. Pharmacological chaperones (PCs) which stabilize mutant GCase have been used to increase lysosomal activity through improving trafficking efficiency. By engineering their inherent basicity, we have synthesized PCs that change conformation between the ER and the lysosomal environment, thus weakening binding to GCase after its successful trafficking to the lysosome. NMR studies confirmed the conformational change while X-ray data reveal bound conformations and binding modes. These results were further corroborated by cell studies showing increases in GCase activity when using the pH-switchable probe at low dosing. Preliminary in vivo assays with humanized mouse models of Gaucher showed enhanced GCase activity levels in relevant tissues, including the brain, further supporting their potential., (© 2022 Wiley-VCH GmbH.)

Background: There is evidence that alterations in functional connectivity (FC) of the striatocortical circuits may appear before the onset of clinical symptoms of Parkinson's disease (PD)., Objective: The aim of this study was to investigate FC of the striatocortical circuitry in asymptomatic carriers of heterozygous glucocerebrosidase (GBA) mutations, which pose a significant risk for developing PD., Methods: Twenty-one parents of confirmed Gaucher disease patients who were carrying heterozygous GBA mutations and 18 healthy individuals matched for age and gender were included. GBA mutation analysis was performed in all participants. Clinical evaluation included neurological examination, Mini Mental State Examination, and UPDRS Part III. Structural and functional MRI data of 18 asymptomatic GBA mutation carriers (asGBAmc) and 17 healthy controls (HC) were available. FC was analyzed with seed-based approach., Results: Eleven asymptomatic mutation carriers had heterozygous p.L483P mutation, 6 subjects heterozygous p.N409S mutation and 1 subject heterozygous p.R392G mutation in GBA gene. Mini-Mental State Examination mean score was 28.77 (±1.16) and 29.64 (±0.70) in asGBAmc and HC groups, respectively (p = 0.012). Significant increased connectivityConclusion:Our results suggest that alterations in striatocortical FC can be detected in asymptomatic heterozygous GBA mutation carriers who are at risk of developing PD. These findings may provide insight into network changes during the asymptomatic phase of PD.

The lysosomal enzyme glucocerebrosidase-1 (GCase) catalyzes the cleavage of a major glycolipid glucosylceramide into glucose and ceramide. The absence of fully functional GCase leads to the accumulation of its lipid substrates in lysosomes, causing Gaucher disease, an autosomal recessive disorder that displays profound genotype-phenotype nonconcordance. More than 250 disease-causing mutations in GBA1 , the gene encoding GCase, have been discovered, although only one of these, N370S, causes 70% of disease. Here, we have used a knowledge-based docking protocol that considers experimental data of protein-protein binding to generate a complex between GCase and its known facilitator protein saposin C (SAPC). Multiscale molecular-dynamics simulations were used to study lipid self-assembly, membrane insertion, and the dynamics of the interactions between different components of the complex. Deep learning was applied to propose a model that explains the mechanism of GCase activation, which requires SAPC. Notably, we find that conformational changes in the loops at the entrance of the substrate-binding site are stabilized by direct interactions with SAPC and that the loss of such interactions induced by N370S and another common mutation, L444P, result in destabilization of the complex and reduced GCase activation. Our findings provide an atomistic-level explanation for GCase activation and the precise mechanism through which N370S and L444P cause Gaucher disease., Competing Interests: The authors declare no conflict of interest.

Background: Gaucher disease is a rare pan-ethnic, lysosomal storage disorder resulting due to beta-Glucosidase (GBA1) gene defect. This leads to the glucocerebrosidase enzyme deficiency and an increased accumulation of undegraded glycolipid glucocerebroside inside the cells' lysosomes. To date, nearly 460 mutations have been described in the GBA1 gene. With the aim to determine mutations spectrum and molecular pathology of Gaucher disease in India, the present study investigated one hundred unrelated patients (age range: 1 day to 31 years) having splenomegaly, with or without hepatomegaly, cytopenia and bone abnormality in some of the patients., Methods: The biochemical investigation for the plasma chitotriosidase enzyme activity and β-Glucosidase enzyme activity confirmed the Gaucher disease. The mutations were identified by screening the patients' whole GBA gene coding region using bidirectional Sanger sequencing., Results: The biochemical analysis revealed a significant reduction in the β-Glucosidase activity in all patients. Sanger sequencing established 71 patients with homozygous mutation and 22 patients with compound heterozygous mutation in GBA1 gene. Lack of identification of mutations in three patients suggests the possibility of either large deletion/duplication or deep intronic variations in the GBA1 gene. In four cases, where the proband died due to confirmed Gaucher disease, the parents were found to be a carrier. Overall, the study identified 33 mutations in 100 patients that also covers four missense mutations (p.Ser136Leu, p.Leu279Val, p.Gly383Asp, p.Gly399Arg) not previously reported in Gaucher disease patients. The mutation p.Leu483Pro was identified as the most commonly occurring Gaucher disease mutation in the study (62% patients). The second common mutations identified were p.Arg535Cys (7% patients) and RecNcil (7% patients). Another complex mutation Complex C was identified in a compound heterozygous status (3% patients). The homology modeling of the novel mutations suggested the destabilization of the GBA protein structure due to conformational changes., Conclusions: The study reports four novel and 29 known mutations identified in the GBA1 gene in one-hundred Gaucher patients. The given study establishes p.Leu483Pro as the most prevalent mutation in the Indian patients with type 1 Gaucher disease that provide new insight into the molecular basis of Gaucher Disease in India.

Some point mutations in β-glucocerebrosidase cause either improper folding or instability of this protein, resulting in Gaucher disease. Pharmacological chaperones bind to the mutant enzyme and stabilize this enzyme; thus, pharmacological chaperone therapy was proposed as a potential treatment for Gaucher disease. The binding affinities of α-1- C -alkyl 1,4-dideoxy-1,4-imino-d-arabinitol (DAB) derivatives, which act as pharmacological chaperones for β-glucocerebrosidase, abruptly increased upon elongation of their alkyl chain. In this study, the primary causes of such an increase in binding affinity were analyzed using protein⁻ligand docking and molecular dynamics simulations. We found that the activity cliff between α-1- C -heptyl-DAB and α-1- C -octyl-DAB was due to the shape and size of the hydrophobic binding site accommodating the alkyl chains, and that the interaction with this hydrophobic site controlled the binding affinity of the ligands well. Furthermore, based on the aromatic/hydrophobic properties of the binding site, a 7-(tetralin-2-yl)-heptyl-DAB compound was designed and synthesized. This compound had significantly enhanced activity. The design strategy in consideration of aromatic interactions in the hydrophobic pocket was useful for generating effective pharmacological chaperones for the treatment of Gaucher disease.

Gaucher disease (GD) is a common lysosomal storage disorder caused by the deficiency of acid β-glucosidase, due to mutations in the GBA gene. To explore the clinical and molecular characteristics of GD patients from Southern China, GBA gene were analyzed by nest PCR and direct Sanger-sequencing. Novel missense mutations were transiently transfected in COS-7 cells by plasmid system for functional verification. Among the 22 GD patients, 19 patients were classified as type 1 and three as type 2. Over 60% of the type 1 patient had the onset before two years of age and about 42% of them died before three years of age. Six type 1 patients with L444P homozygous genotype, presented with early onset and severe hepatosplenomegaly. Four novel mutations Y22C, F109L, L149F and c.983_990delCCCACTGG were identified. The GBA activities in vitro of novel mutants Y22C, F109L and L149F were 20.2%, 6.9% and 6.5% of the wild-type, respectively. L444P mutation accounted for 47.7% of the mutant alleles. Our results revealed that type 1 GD tends to present with a severe phenotype among southern Chinese. L444P was the most prevalent mutation and L444P homozygous genotype was associated with severe type 1 GD. Three novel missense mutations identified were pathogenic., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Gaucher disease is caused by the defective catabolism of the simple glycosphingolipid, glucosylceramide (GlcCer), due to mutations in the GBA1 gene which encodes for acid β-glucosidase (GCase), the lysosomal enzyme that degrades GlcCer. Today, Gaucher disease patients are routinely treated with recombinant GCase, in a treatment regimen known as enzyme replacement therapy (ERT). We now review the biochemical basis of ERT and discuss how this treatment has advanced since it was first pioneered by Dr. Roscoe Brady in the 1960s. We will place particular emphasis on the three dimensional structure of GCase, and subsequently discuss a relatively new treatment paradigm, substrate reduction therapy (SRT), in which GlcCer synthesis is partially inhibited, thus reducing its accumulation. Both of these approaches are based on studies and concepts developed by Dr. Brady over his remarkable research career spanning six decades., (Copyright © 2016 Elsevier Inc. All rights reserved.)

In Gaucher disease (GD), mutant lysosomal acid β-glucocerebrosidase fails to properly hydrolyze its substrate, glucosylceramide, which accumulates in the lysosomes. Due to its phenotypic heterogeneity, GD has been classified into type 1, non-neuronopathic, and types 2 and 3, the neuronopathic forms, based on the primary involvement of the central nervous system. Neuroinflammation and necroptotic death may appear in the neuronopathic forms of GD, whereas type 1 GD patients may develop Parkinson disease (PD), a prototype of protein misfolding disorders of the nervous system. PD is significantly more prevalent among GD carriers and patients than among the non-GD populations. It is apparent that the amount of mutant enzyme present in lysosomes depends on the amount of mutant enzyme recognized as correctly folded in the endoplasmic reticulum (ER) for physiologically correct transport through the Golgi apparatus to the lysosome. Mutant enzyme recognized as misfolded is retained in the ER, inducing the Unfolded Protein Response. In the current review, we present three discrete areas of interest: molecular and cellular mechanisms underlying the association between GD and PD; the clinical and genetic associations between GD and PD; and treatment options for GD. We also discuss the relevance of induced pleuripotent stem cells to the above associations., (© 2016 WILEY PERIODICALS, INC.)

Background: Gaucher's disease (GD) is an autosomal recessive disorder caused by a deficiency of acid β-glucosidase (glucocerebrosidase [GBA]) that results in the accumulation of glucocerebroside within macrophages. Many mutations have been reported to be associated with this disorder. This study aimed to discover more mutations and provide data for the genetic pattern of the gene, which will help the development of quick and accurate genetic diagnostic tools for this disease., Methods: Genomic DNA was obtained from peripheral blood leukocytes of the patient and Sanger sequencing is used to sequence GBA gene. Sequence alignments of mammalian β-GBA (GCase) and three-dimensional protein structure prediction of the mutation were made. A construct of this mutant and its compound heterozygous counterpart were used to measure GCase in vitro., Results: GCase is relatively conserved at p.T219A. This novel mutation differs from its wild-type in structure. Moreover, it also causes a reduction in GCase enzyme activity., Conclusion: This novel mutation (c.655A>G, p.T219A) is a pathogenic missense mutation, which contributes to GD.

Mutations in the gene for the lysosomal enzyme glucocerebrosidase (GCase) cause Gaucher disease and are the most common risk factor for Parkinson disease (PD). Analytical ultracentrifugation of 8 μM GCase shows equilibrium between monomer and dimer forms. However, in the presence of its co-factor saposin C (Sap C), only monomer GCase is seen. Isothermal calorimetry confirms that Sap C associates with GCase in solution in a 1:1 complex (Kd = 2.1 ± 1.1 μM). Saturation cross-transfer NMR determined that the region of Sap C contacting GCase includes residues 63-66 and 74-76, which is distinct from the region known to enhance GCase activity. Because α-synuclein (α-syn), a protein closely associated with PD etiology, competes with Sap C for GCase binding, its interaction with GCase was also measured by ultracentrifugation and saturation cross-transfer. Unlike Sap C, binding of α-syn to GCase does not affect multimerization. However, adding α-syn reduces saturation cross-transfer from Sap C to GCase, confirming displacement. To explore where Sap C might disrupt multimeric GCase, GCase x-ray structures were analyzed using the program PISA, which predicted stable dimer and tetramer forms. For the most frequently predicted multimer interface, the GCase active sites are partially buried, suggesting that Sap C might disrupt the multimer by binding near the active site., (Published by Elsevier Inc.)

The acid β-glucosidase (glucocerbrosidase (GCase)) binding sequence to LIMP-2 (lysosomal integral membrane protein 2), the receptor for intracellular GCase trafficking to the lysosome, has been identified. Heterologous expression of deletion constructs, the available GCase crystal structures, and binding and co-localization of identified peptides or mutant GCases were used to identify and characterize a highly conserved 11-amino acid sequence, DSPIIVDITKD, within human GCase. The binding to LIMP-2 is not dependent upon a single amino acid, but the interactions of GCase with LIMP-2 are heavily influenced by Asp(399) and the di-isoleucines, Ile(402) and Ile(403). A single alanine substitution at any of these decreases GCase binding to LIMP-2 and alters its pH-dependent binding as well as diminishing the trafficking of GCase to the lysosome and significantly increasing GCase secretion. Enterovirus 71 also binds to LIMP-2 (also known as SCARB2) on the external surface of the plasma membrane. However, the LIMP-2/SCARB2 binding sequences for enterovirus 71 and GCase are not similar, indicating that LIMP-2/SCARB2 may have multiple or overlapping binding sites with differing specificities. These findings have therapeutic implications for the production of GCase and the distribution of this enzyme that is delivered to various organs., (© 2014 by The American Society for Biochemistry and Molecular Biology, Inc.)

Gaucher disease is an autosomal recessive lysosomal disorder characterized by the accumulation of glucosylceramide as a result of a deficiency of the enzyme glucocerebrosidase. Several competitive glucocerebrosidase inhibitors are able to act as pharmacological chaperones for an efficient rescue of the mutated, misfolded forms of the enzyme. Along this line, we report in this work on the ability of several aminocyclitols to increase the residual glucocerebrosidase activity in patient fibroblasts with different genotypes. Some of the compounds were slightly active on fibroblasts bearing some mutations, including the highly prevalent N370S mutation. All compounds were highly active as enzyme activity enhancers on fibroblasts from Gaucher disease patients containing the G202R mutation. Moreover, using the novel tagged sphingolipid ω-azidosphingosine, a reduction in the tagged glucosylceramide accumulation was also observed for selected aminocyclitols. Attempts to explain the activity impairment observed in glucocerebrosidase bearing the G202R mutation by comparative molecular dynamic studies on wild type and the G202R mutated proteins (free and isofagomine-bound, in both cases) were unsuccessful. Under the simulation conditions used, no clear effect of the G202R mutation neither over the global structure of the protein nor on the loops that constitute the glucocerebrosidase active site was observed. Since the G202R residue is located on the protein surface, altered protein-membrane or protein-protein interactions could account for the observed differences. In conclusion, we have tested novel compounds that have shown some chaperone effect on particular glucocerebrosidase mutant enzymes, supporting the enhancement therapy as an alternative approach for Gaucher disease., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The main objective of our study is to develop a simple, fast and reliable method for measuring β-glucocerebrosidase activity in Gaucher patients leukocytes in clinical practice. This measurement may be a useful marker to drive dose selection and early clinical decision making of enzyme replacement therapy. We measure the enzyme activity by high-performance liquid chromatography with ultraviolet detection and 4-nitrophenyl-β-d-glucopyranoside as substrate. A cohort of eight Gaucher patients treated with enzyme replacement therapy and ten healthy controls were tested; median enzyme activity values was 20.57mU/ml (interquartile range 19.92-21.53mU/ml) in patients and mean was 24.73mU/ml (24.12-25.34mU/ml) in the reference group, which allowed the establishment of the normal range of β-glucocerebrosidase activity. The proposed method for leukocytes glucocerebrosidase activity measuring is fast, easy to use, inexpensive and reliable. Furthermore, significant differences between both populations were observed (p=0.008). This suggests that discerning between patients and healthy individuals and providing an approach to enzyme dosage optimization is feasible. This method could be considered as a decision support tool for clinical monitoring. Our study is a first approach to in depth analysis of enzyme replacement therapy and optimization of dosing therapies., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Lysosomal storage diseases (LSDs) are often caused by mutations compromising lysosomal enzyme folding in the endoplasmic reticulum (ER), leading to degradation and loss of function. Mass spectrometry analysis of Gaucher fibroblasts treated with mechanistically distinct molecules that increase LSD enzyme folding, trafficking, and function resulted in the identification of nine commonly downregulated and two jointly upregulated proteins, which we hypothesized would be critical proteostasis network components for ameliorating loss-of-function diseases. LIMP-2 and FK506 binding protein 10 (FKBP10) were validated as such herein. Increased FKBP10 levels accelerated mutant glucocerebrosidase degradation over folding and trafficking, whereas decreased ER FKBP10 concentration led to more LSD enzyme partitioning into the calnexin profolding pathway, enhancing folding and activity to levels thought to ameliorate LSDs. Thus, targeting FKBP10 appears to be a heretofore unrecognized therapeutic strategy to ameliorate LSDs., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The purpose of this pilot was to assess the tolerability and efficacy of ambroxol as a pharmacological chaperone in patients with symptomatic, type 1 Gaucher disease who present with measurable disease parameters but are not receiving enzyme replacement therapy (ERT) in order to provide proof of concept and/or ascertain the suitability of ambroxol for a larger clinical trial. The Israeli Ministry of Health Form 29c was employed to prescribe ambroxol for off-label use. Twelve patients were dispensed 2 capsules of 75 mg of ambroxol daily for 6 months. There were 8 females (66.7%). Mean age at entry was 41.1 (range: 24-63) years. Mean body weight at entry was 66.4 (range: 46.5-100) kg. One patient withdrew because of a hypersensitivity reaction, one because of elective splenectomy. No patient experienced clinically relevant deterioration in disease parameters measured. One patient achieved a robust response relative to baseline: +16.2% hemoglobin; +32.9% platelets; -2.8% liver volume; and -14.4% spleen volume. Three patients, including the above one, elected to continue on ambroxol for a further 6 months: hemoglobin levels and liver volumes were relatively stable, but platelet counts further increased in the above patient (+52.6% from baseline) and spleen volumes decreased further in all three patients (-6.4%, -18.6%, and -23.4% from baseline). Thus, ambroxol may be a safe option for Gaucher disease patients with potential disease-specific efficacy and should be expanded into a clinical trial using higher doses and placebo-controlled design., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Gaucher disease (GD) is characterized by accumulation of glucosylceramide in lysosomes due to mutations in the GBA1 gene encoding the lysosomal hydrolase β-glucocerebrosidase (GCase). The disease has a broad spectrum of phenotypes, which were divided into three different Types; Type 1 GD is not associated with primary neurological disease while Types 2 and 3 are associated with central nervous system disease. GCase molecules are synthesized on endoplasmic reticulum (ER)-bound polyribosomes, translocated into the ER and following modifications and correct folding, shuttle to the lysosomes. Mutant GCase molecules, which fail to fold correctly, undergo ER associated degradation (ERAD) in the proteasomes, the degree of which is one of the factors that determine GD severity. Several pharmacological chaperones have already been shown to assist correct folding of mutant GCase molecules in the ER, thus facilitating their trafficking to the lysosomes. Ambroxol, a known expectorant, is one such chaperone. Here we show that ambroxol increases both the lysosomal fraction and the enzymatic activity of several mutant GCase variants in skin fibroblasts derived from Type 1 and Type 2 GD patients., (Copyright © 2012 Elsevier Inc. All rights reserved.)

An asparagine-to-serine substitution at residue 370 (N370S) in glucocerebrosidase (GCase) is the most prevalent mutation leading to Gaucher's disease, the most common lysosomal storage disorder. Two types of hydrogen/deuterium exchange experiment coupled with proteolysis and liquid chromatography-mass spectrometry (HDX-MS) were used to investigate the dynamic properties and unfolding stability of wt, R495H, and N370S GCases in the presence and absence of ligands. R495H GCase is used for enzyme replacement therapy and is considered to be a wt surrogate, whereas N370S is the most prevalent mutation leading to Gaucher's disease. Time-course HDX experiments of the GCases were performed under near-physiological conditions to detect the protein's local unfolding motions at a submolecular level. In guanidine-titration experiments, HDX reactions were performed with various concentrations of a chemical denaturant to provide the global stability of the proteins. The two types of experiment showed that all three purified GCases, wt, R495H, and N370S, have virtually identical local unfolding motions and global stabilities in solution. Combined with previous X-ray crystallographic studies, which showed indistinguishable backbone conformations for N370S and R495H GCase mutants and very similar melting temperatures for the wt, R495H, and N370S mutants, all three GCases are likely to have virtually identical structural and dynamic properties in solution. The guanidine-titration experiments revealed that the pharmacological chaperone, isofagomine (IFG), interacts more weakly with the N370S mutant than with the R495H GCase; this is consistent with the higher IC(50) value of IFG against N370S than against R495H. The time-course experiments showed that IFG restricts the local unfolding motions of N370S in the same way as those of R495H when the ligand saturates the proteins., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Gaucher's disease (GD) is a rare autosomal recessive (AR) disorder characterized by a deficiency of glucocerebrosidase (glucosylceramidase, acid β-glucosidase). This enzyme deficiency results in an accumulation of sphingolipids in the cells of GD patients, which may contribute to the dysregulation of the immune system, B-cell dysfunction and expression of specific cytokines such as interleukin (IL) -1, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF). Accumulated substrate may directly affect the patient's immunity and pose a higher risk for cancer, especially hematologic malignancies. However, recent large-scale studies suggest that the relative risks of GD and hematologic malignancies are not statistically significant and, therefore, their association with each other remains controversial. In this report, we present the first Asian GD case where the patient was simultaneously diagnosed with a non-Hodgkin's lymphoma. A renal biopsy confirmed that the patient had diffuse large B-cell lymphoma (DLBCL). A bone marrow study during lymphoma staging revealed Gaucher cells with abundant fibrillary, blue-gray cytoplasm and a wrinkled, tissue paper-like appearance. Subsequently, an acid β-glucosidase (GbA) gene mutation study demonstrating two heterozygote mutations, G202R (c.721G>A; p.G241R), a known pathogenic mutation, and a novel mutation R277C (c.946C>T; p.R316C) prompted the diagnosis of GD. Previous case reports have demonstrated concurrent GD and lymphoma in type 1 GD patients, with 40% of patients diagnosed with GD when a lymphoma is detected during disease evaluation. In Korea, GD cases with the G202R gene mutation have been reported in neuropathic patients with a very low frequency. To our knowledge, this case represents the first observation of the G202R mutation in a type 1 GD patient associated with lymphoma. Furthermore, this report is the first patient with DLBCL with kidney involvement along with GD.

A series of N-substituted ε-hexonolactams have been designed and prepared by a concise route with a tandem ring-expansion reaction as the key step. Some of the N-substituted ε-hexonolactams show better enhancements to N370S mutant β-glucocerebrosidase activity than NB-DNJ and NN-DNJ. Both the experimental results and computational studies highlight the importance of the carbonyl group for stabilizing protein folds in the mutant enzyme. The structure-activity relationships are also discussed. These novel N-alkylated iminosugars are promising pharmacological chaperones for the treatment of N370S mutant Gaucher disease., (This journal is © The Royal Society of Chemistry 2012)

Gaucher disease (GD) is a disorder of glycosphingolipid metabolism caused by deficiency of lysosomal glucocerebrosidase (GlcCerase) activity, due to conformationally or functionally defective variants, resulting in progressive deposition of glycosylceramide in macrophages. The glucose analogue, N-butyldeoxynojirimycin (NB-DNJ, miglustat), is an inhibitor of the ceramide-specific glycosyltransferase, which catalyzes the first step of glycosphingolipid biosynthesis and is currently approved for the oral treatment of type 1 GD. In a previous work, we found a GlcCerase activity increase in cell cultures in the presence of NB-DNJ, which could imply that this compound is not only a substrate reducer but also a pharmacological chaperone or inhibitor for GlcCerase degradation. In this work we compare imiglucerase (the enzyme currently used for replacement therapy) and velaglucerase alfa (a novel therapeutic enzyme form) in terms of conformational stability and enzymatic activity, as well as the effect of NB-DNJ on them. The interaction between these enzymes and NB-DNJ was studied by isothermal titration calorimetry. Our results reveal that, although velaglucerase alfa and imiglucerase exhibit very similar activity profiles, velaglucerase alfa shows higher in vitro thermal stability and is less prone to aggregation/precipitation, which could be advantageous for storage and clinical administration. In addition, we show that at neutral pH NB-DNJ binds to and enhances the stability of both enzymes, while at mildly acidic lysosomal conditions it does not bind to them. These results support the potential role of NB-DNJ as a pharmacological chaperone, susceptible of being part of pharmaceutical formulation or combination therapy for GD in the future.

Recently, two studies were published that examined the structure of the acid-β-glucosidase N370S mutant, the most common mutant that causes Gaucher disease. One study used the experimental tool of X-ray crystallography, and the other utilized molecular dynamics (MD). The two studies reinforced each other through the similarities in their findings, but each approach also added some unique information. Both studies report that the conformation of active site loop 3 changes, due to an altered hydrogen bonding network; however, the MD study produced additional data concerning the flexibility of loop 1 and the catalytic residues that are not observed in the other study.

The hallmark of Gaucher's disease cellular pathogenesis is the lysosomal accumulation of glucosylceramide, which is caused by misfolding of mutated glucocerebrosidase (GC) and loss of lysosomal GC activity, and leads to depletion of [Ca(2+)](ER). We demonstrate that modulation of Ca(2+) homeostasis and enhancement of the cellular folding capacity synergize to rescue the folding of mutated GC variants. Lacidipine, an L-type Ca(2+) channel blocker that also inhibits [Ca(2+)](ER) efflux, enhances folding, trafficking, and activity of degradation-prone GC variants. Lacidipine remodels mutated GC proteostasis by simultaneously activating a series of distinct molecular mechanisms, namely modulation of Ca(2+) homeostasis, upregulation of the ER chaperone BiP, and moderate induction of the unfolded protein response. However, unlike previously reported proteostasis regulators, lacidipine treatment is not cytotoxic but prevents apoptosis induction typically associated with sustained activation of the unfolded protein response., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Four diastereomeric series of N-alkylated [6+5] bicyclic isoureas having hydroxyl substituents mimicking glucose hydroxyl groups have been synthesized as potential β-glucocerebrosidase (GCase) inhibitors with the aim of developing pharmacological chaperones for enzyme deficiency in Gaucher disease (GD). The bicyclic compounds differ either by the configuration of the ring fusion carbon atoms or by the nature of the N-alkyl substituents. When assayed for effects on GCase activity, the isoureas displayed selective inhibition of GCase with low micromolar to nanomolar IC(50)'s in isolated enzyme experiments. One of the series of isoureas, a family having a specific cis ring fusion, exhibited strong inhibition of recombinant GCase activity with K(i) values in the 2-42 nM range. In addition, the [6+5] bicyclic guanidine derivatives with a substitution pattern analogous to the most active isoureas were also found to be potent inhibitors of GCase with K(i) values between 3 and 10 nM. Interestingly, the active bicyclic isoureas and guanidines also behaved as GCase inhibitors in wild-type human fibroblasts at nanomolar concentrations. The potential of these compounds as pharmaceutical chaperones was determined by analyzing their capacity for increasing GCase activity in GD lymphoblasts derived from N370S and L444P variants, two of the most prevalent Gaucher mutations. Six compounds were selected from the different bicyclic isoureas and guanidines obtained that increased GCase activity by 40-110% in N370S and 10-50% in L444P cells at low micromolar to nanomolar concentrations following a 3 day incubation. These results describe a promising series of potent GCase ligands having the cellular properties required for pharmacological chaperones., (© 2011 American Chemical Society)

In Gaucher disease (GD), the inherited deficiency of glucocerebrosidase results in the accumulation of glucocerebroside within lysosomes. Although almost 300 mutations in the glucocerebrosidase gene (GBA) have been identified, the ability to predict phenotype from genotype is quite limited. In this study, we sought to examine potential GBA transcriptional regulatory elements for variants that contribute to phenotypic diversity. Specifically, we generated the genomic sequence for the orthologous genomic region ( approximately 39.4kb) encompassing GBA in eight non-human mammals. Computational comparisons of the resulting sequences, using human sequence as the reference, allowed the identification of multi-species conserved sequences (MCSs). Further analyses predicted the presence of two putative clusters of transcriptional regulatory elements upstream and downstream of GBA, containing five and three transcription factor-binding sites (TFBSs), respectively. A firefly luciferase (Fluc) reporter construct containing sequence flanking the GBA gene was used to test the functional consequences of altering these conserved sequences. The predicted TFBSs were individually altered by targeted mutagenesis, resulting in enhanced Fluc expression for one site and decreased expression for seven others sites. Gel-shift assays confirmed the loss of nuclear-protein binding for several of the mutated constructs. These identified conserved non-coding sequences flanking GBA could play a role in the transcriptional regulation of the gene contributing to the complexity underlying the phenotypic diversity seen in GD., (Published by Elsevier Inc.)

The N188S mutation in Gaucher disease is associated with myoclonus epilepsy. We performed genetic analysis on a patient with progressive myoclonus epilepsy, who had received antiepileptic drugs for over 10 years. We detected N188S/G199D on the gene encoding glucocerebrosidase. Mutant proteins carrying each mutation were expressed in COS-1 cells (a commonly used cell line which derives from kidney cells of the African green monkey). Measurements of enzymatic activity and Western blotting analysis were performed. When residual activities were measured, glucocerebrosidase with the N188S mutation exhibited 50% activity of the wild type, and with G199D, 7.4%. Neither mutation influenced the stability of the enzyme protein. These data suggested a diagnosis of Gaucher disease for this patient, and indicated that G199D is a novel mutation.

Gaucher disease (GD), the most prevalent lysosomal storage disorder, is caused by mutations of lysosomal beta-glucosidase (acid beta-Glu, beta-glucocerebrosidase); these mutations result in protein misfolding. Some inhibitors of this enzyme, such as the iminosugar glucomimetic N-(n-nonyl)-1-deoxynojirimycin (NN-DNJ), are known to bind to the active site and stabilize the proper folding for the catalytic form, acting as "chemical chaperones" that facilitate transport and maturation of acid beta-Glu. Recently, bicyclic nojirimycin (NJ) analogues with structure of sp2 iminosugars were found to behave as very selective, competitive inhibitors of the lysosomal beta-Glu. We have now evaluated the glycosidase inhibitory profile of a series of six compounds within this family, namely 5-N,6-O-(N'-octyliminomethylidene-NJ (NOI-NJ), the 6-thio and 6-amino-6-deoxy derivatives (6S-NOI-NJ and 6N-NOI-NJ) and the corresponding galactonojirimycin (GNJ) counterparts (NOI-GNJ, 6S-NOI-GNJ and 6N-NOI-GNJ), against commercial as well as lysosomal glycosidases. The chaperone effects of four selected candidates (NOI-NJ, 6S-NOI-NJ, 6N-NOI-NJ, and 6S-NOI-GNJ) were further evaluated in GD fibroblasts with various acid beta-Glu mutations. The compounds showed enzyme enhancement on human fibroblasts with N188S, G202R, F213I or N370S mutations. The chaperone effects of the sp2 iminosugar were generally stronger than those observed for NN-DNJ; this suggests that these compounds are promising candidates for clinical treatment of GD patients with a broad range of beta-Glu mutations, especially for neuronopathic forms of Gaucher disease.

Gaucher disease (GD), the most prevalent lysosomal storage disease, is caused by a deficiency of glucocerebrosidase (GCase). The identification of small molecules acting as agents for enzyme enhancement therapy is an attractive approach for treating different forms of GD. A thermal denaturation assay utilizing wild type GCase was developed to screen a library of 1,040 Food and Drug Administration-approved drugs. Ambroxol (ABX), a drug used to treat airway mucus hypersecretion and hyaline membrane disease in newborns, was identified and found to be a pH-dependent, mixed-type inhibitor of GCase. Its inhibitory activity was maximal at neutral pH, found in the endoplasmic reticulum, and undetectable at the acidic pH of lysosomes. The pH dependence of ABX to bind and stabilize the enzyme was confirmed by monitoring the rate of hydrogen/deuterium exchange at increasing guanidine hydrochloride concentrations. ABX treatment significantly increased N370S and F213I mutant GCase activity and protein levels in GD fibroblasts. These increases were primarily confined to the lysosome-enriched fraction of treated cells, a finding confirmed by confocal immunofluorescence microscopy. Additionally, enhancement of GCase activity and a reduction in glucosylceramide storage was verified in ABX-treated GD lymphoblasts (N370S/N370S). Hydrogen/deuterium exchange mass spectrometry revealed that upon binding of ABX, amino acid segments 243-249, 310-312, and 386-400 near the active site of GCase are stabilized. Consistent with its mixed-type inhibition of GCase, modeling studies indicated that ABX interacts with both active and non-active site residues. Thus, ABX has the biochemical characteristics of a safe and effective enzyme enhancement therapy agent for the treatment of patients with the most common GD genotypes.

Gaucher disease is an autosomal recessive disorder. It is characterized by the accumulation of glucosylceramide in lysosomes of mononuclear phagocyte system, attributable to acid beta-glucosidase deficiency. The main consequences of this disease are hepatosplenomegaly, skeletal lesions and, sometimes, neurological manifestations. At sub-inhibitory concentrations, several competitive inhibitors act as chemical chaperones by inducing protein stabilization and increasing enzymatic activity. Here we tested two iminosugars (NB-DNJ and NN-DNJ) and four aminocyclitols with distinct degrees of lipophilicity as pharmacological chaperones for glucocerebrosidase (GBA). We report an increase in the activity of GBA using NN-DNJ, NB-DNJ and aminocyclitol 1 in stably transfected cell lines, and an increment with NN-DNJ and aminocyclitol 4 in patient fibroblasts. These results on specific mutations validate the use of chemical chaperones as a therapeutic approach for Gaucher disease. However, the development and analysis of new compounds is required in order to find more effective therapeutic agents that are active on a broader range of mutations.

Point mutations in beta-glucocerebrosidase (GCase) can result in a deficiency of both GCase activity and protein in lysosomes thereby causing Gaucher Disease (GD). Enzyme inhibitors such as isofagomine, acting as pharmacological chaperones (PCs), increase these levels by binding and stabilizing the native form of the enzyme in the endoplasmic reticulum (ER), and allow increased lysosomal transport of the enzyme. A high-throughput screen of the 50,000-compound Maybridge library identified two, non-carbohydrate-based inhibitory molecules, a 2,4-diamino-5-substituted quinazoline (IC(50) 5 microM) and a 5-substituted pyridinyl-2-furamide (IC(50) 8 microM). They raised the levels of functional GCase 1.5-2.5-fold in N370S or F213I GD fibroblasts. Immunofluorescence confirmed that treated GD fibroblasts had decreased levels of GCase in their ER and increased levels in lysosomes. Changes in protein dynamics, monitored by hydrogen/deuterium-exchange mass spectrometry, identified a domain III active-site loop (residues 243-249) as being significantly stabilized upon binding of isofagomine or either of these two new compounds; this suggests a common mechanism for PC enhancement of intracellular transport.

In mammalian cells, glucosylceramide (GlcCer), the simplest glycosphingolipid, is hydrolyzed by the lysosomal enzyme acid beta-glucosidase (GlcCerase). In the human metabolic disorder Gaucher disease, GlcCerase activity is significantly decreased owing to one of approximately 200 mutations in the GlcCerase gene. The most common therapy for Gaucher disease is enzyme replacement therapy (ERT), in which patients are given intravenous injections of recombinant human GlcCerase; the Genzyme product Cerezyme has been used clinically for more than 15 years and is administered to approximately 4000 patients worldwide. Here we review the crystal structure of Cerezyme and other recombinant forms of GlcCerase, as well as of their complexes with covalent and non-covalent inhibitors. We also discuss the stability of Cerezyme, which can be altered by modification of its N-glycan chains with possible implications for improved ERT in Gaucher disease.

Gaucher disease, the most prevalent lysosomal storage disorder, is principally caused by malfunction of the lysosomal enzyme glucocerebrosidase (GBA), a 497-amino acid membrane glycoprotein that catalyzes the hydrolysis of glucosylceramide to ceramide and glucose in the presence of an essential 84-residue activator peptide named saposin C (SapC). Knowledge of the GBA structure, a typical (beta/alpha)(8) TIM barrel, explains the effect of few mutations, directly affecting or located near the catalytic site. To identify new regions crucial for proper GBA functionality, we analyzed the interactions of the enzyme with a second (substrate) and a third (cofactor) partner. We build 3D docking models of the GBA-SapC and the GBA-ceramide interactions, by means of methodologies that integrate both evolutive and structural information. The GBA-SapC docking model confirm the implication of three spatially closed regions of the GBA surface (TIM barrel-helix 6 and helix 7, and the Ig-like domain) in binding the SapC molecule. This model provides new basis to understand the pathogenicity of several mutations, such as the prevalent Leu444Pro, and the additive effect of Glu326Lys in the double mutant Glu326Lys-Leu444Pro. Overall, 39 positions in which amino acid changes are known to cause Gaucher disease were localized in the GBA regions identified in this work. Our model is discussed in relation to the phenotype (pathogenic effect) of these mutations, as well as to the enzymatic activity of the recombinant proteins when available. Both data fully correlates with the proposed model, which will provide a new tool to better understand Gaucher disease and to design new therapy strategies., ((c) 2007 Wiley-Liss, Inc.)

We report a sensitive method to detect point mutations in proteins from complex samples. The method is based on surface-enhanced laser desorption/ionization time-of-flight (SELDI-ToF) MS but can be extended to other MS platforms. The target protein in this study is the lysosomal enzyme glucocerebrosidase (GC), the key enzyme in Gaucher's disease. Deficiency of GC activity results in accumulation of glucosylceramide in macrophages. The relationship between GC genotypes and Gaucher's patient phenotypes is not strict. The possibility to measure protein levels of GC in clinical samples may provide deeper insight into the phenomenology of Gaucher's disease. For this purpose, GC was isolated in a single enrichment step through interaction with an immobilized monoclonal antibody, 8E4. After on-chip digestion of the antibody-antigen complex with trypsin, a total of 25 GC peptides were identified (sequence coverage approximately 60%), including several peptides containing mutated amino acid residues. The described methodology allows mutational analysis on the protein level, directly measured on complex biological samples without the necessity of elaborate purification procedures.

Gaucher disease is an autosomal recessive lysosomal storage disorder due to deficiency of the lysosomal enzyme glucocerebrosidase. Three clinical phenotypes, type 1, nonneuronopathic; and types 2 and 3, acute and subacute neuronopathic are recognized. The incidence of Gaucher disease in the Thai population is unknown, but likely under-diagnosed. We performed molecular analysis in four patients, from three sibships, with type 3 Gaucher disease. Four mutant glucocerebrosidase (GBA) alleles were identified including two novel splice site mutations, IVS6-1G>C and IVS9-3C>G; both are predicted to result in truncated protein products, p.F255fsX256, and p.K464fsX487 and p.S463fsX480, respectively. One patient, homozygous for the L444P point mutation, had a "Norbottnian-like" phenotype, with more severe visceral involvement, kyphosis, barreled chest, and no neurological involvement other than supranuclear gaze palsy. These molecular studies of neuronopathic Gaucher disease will provide additional genotype-phenotype correlation particularly in non-Caucasian population.

Gaucher disease is a lysosomal storage disorder caused by deficiency of human acid beta-glucosidase. Recent x-ray structural elucidation of the enzyme alone and in the presence of its inhibitor was done, which provided an excellent template for further studies on the binding of substrate, product and inhibitor. To draw correlations between the clinical manifestation of the disease driven by point mutations, L444P and L444R, and the placement and function of putative S-binding sites, the presented theoretical studies were undertaken, which comprised of molecular dynamics and molecular docking methods. The obtained results indicate the D443 and D445 residues as extremely important for physiological functionality of an enzyme. They also show, although indirectly, that binding of the substrate is influenced by an interplay of E235 and E334 residues, constituting putative substrate binding site, and the region flanked by D435 and D445 residues.

We briefly introduce the most common lysosomal storage disorder, Gaucher disease, concisely describe the Food and Drug Administration approved strategies to ameliorate Gaucher disease, and then outline the emerging pharmacologic chaperone strategy that offers the promise to remedy this malady.

Gaucher disease is caused by mutations in the gene encoding acid beta-glucosidase (GlcCerase), resulting in glucosylceramide (GlcCer) accumulation. The only currently available orally administered treatment for Gaucher disease is N-butyl-deoxynojirimycin (Zavesca, NB-DNJ), which partially inhibits GlcCer synthesis, thus reducing levels of GlcCer accumulation. NB-DNJ also acts as a chemical chaperone for GlcCerase, although at a different concentration than that required to completely inhibit GlcCer synthesis. We now report the crystal structures, at 2A resolution, of complexes of NB-DNJ and N-nonyl-deoxynojirimycin (NN-DNJ) with recombinant human GlcCerase, expressed in cultured plant cells. Both inhibitors bind at the active site of GlcCerase, with the imino sugar moiety making hydrogen bonds to side chains of active site residues. The alkyl chains of NB-DNJ and NN-DNJ are oriented toward the entrance of the active site where they undergo hydrophobic interactions. Based on these structures, we make a number of predictions concerning (i) involvement of loops adjacent to the active site in the catalytic process, (ii) the nature of nucleophilic attack by Glu-340, and (iii) the role of a conserved water molecule located in a solvent cavity adjacent to the active site. Together, these results have significance for understanding the mechanism of action of GlcCerase and the mode of GlcCerase chaperoning by imino sugars.

NIH researchers report results of a qHTS hunt for new chemical chaperones for the treatment of Gaucher disease.

Although Gaucher disease is a rare disorder, recent developments in novel means for therapeutic intervention have invigorated both academic research and pharmaceutical industry discovery programmes. The common mutations found in the lysosomal enzyme deficient in Gaucher disease, beta-glucocerebrosidase, earmark these proteins for destruction by the endoplasmic reticulum-localised protein folding machinery, resulting in enzyme insufficiency, lysosomal glycolipid storage and subsequent pathology. However, many of these mutants can be rescued from global misfolding to preserve glycolipid substrate binding and eventual catalysis in the lysosome, by the addition of subinhibitory concentrations of pharmacologically active small molecules. This novel, chaperon-mediated approach has benefited from insights into the molecular understanding of beta-glucocerebrosidase structure, drug design and development in cellular models for disease.

Gaucher disease results from mutations in the lysosomal enzyme acid beta-glucosidase (GCase). Although enzyme replacement therapy has improved the health of some affected individuals, such as those with the prevalent N370S mutation, oral treatment with pharmacological chaperones may be therapeutic in a wider range of tissue compartments by restoring sufficient activity of endogenous mutant GCase. Here we demonstrate that isofagomine (IFG, 1) binds to the GCase active site, and both increases GCase activity in cell lysates and restores lysosomal trafficking in cells containing N370S mutant GCase. We also compare the crystal structures of IFG-bound GCase at low pH with those of glycerol-bound GCase at low pH and apo-GCase at neutral pH. Our data indicate that IFG induces active GCase, which is secured by interactions with Asn370. The design of small molecules that stabilize substrate-bound conformations of mutant proteins may be a general therapeutic strategy for diseases caused by protein misfolding and mistrafficking.

Gaucher disease is caused by mutations in the gene encoding acid-beta-glucosidase. A recombinant form of this enzyme, Cerezyme, is used to treat Gaucher disease patients by ;enzyme-replacement therapy'. Crystals of Cerezyme after its partial deglycosylation were obtained earlier and the structure was solved to 2.0 A resolution [Dvir et al. (2003), EMBO Rep. 4, 704-709]. The crystal structure of unmodified Cerezyme is now reported, in which a substantial number of sugar residues bound to three asparagines via N-glycosylation could be visualized. The structure of intact fully glycosylated Cerezyme is virtually identical to that of the partially deglycosylated enzyme. However, the three loops at the entrance to the active site, which were previously observed in alternative conformations, display additional variability in their structures. Comparison of the structure of acid-beta-glucosidase with that of xylanase, a bacterial enzyme from a closely related protein family, demonstrates a close correspondence between the active-site residues of the two enzymes.

Acid beta-glucosidase (GCase) is a 497-amino acid, membrane-associated lysosomal exo-beta-glucosidase whose defective activity leads to the Gaucher disease phenotypes. To move toward a structure/function map for disease mutations, 52 selected single amino acid substitutions were introduced into GCase, expressed in an insect cell system, purified, and characterized for basic kinetic, stability, and activator response properties. The variant GCases from Gaucher disease patients and selected variant GCases from the mouse had decreased relative k(cat) and differential effects on active site binding and/or attachment of mechanism-based covalent (conduritol B epoxide) or reversible (deoxynojirimycin derivatives) inhibitors. A defect in negatively charged phospholipid activation was present in the majority of variant GCases but was increased in two, N370S and V394L. Deficits in saposin C enhancement of k(cat) were present in variant GCases involving residues 48-122, whereas approximately 2-fold increases were obtained with the L264I GCase. About 50% of variant GCases each had wild-type or increased sensitivity to in vitro cathepsin D digestion. Mapping of these properties onto the crystal structures of GCase indicated wide dispersion of functional properties that can affect catalytic function and stability. Site-directed mutagenesis of cysteine residues showed that the disulfide bonds, Cys(4)-Cys(16) and Cys(18)-Cys(23), and a free Cys(342) were essential for activity; the free Cys(126) and Cys(248) were not. Relative k(cat) was highly sensitive to a His substitution at Arg(496) but not at Arg(495). These studies and high phylogenetic conservation indicate localized and general structural effects of Gaucher disease mutations that were not obvious from the nature of the amino acid substitution, including those predicted to be nondisruptive (e.g. Val --> Leu). These results provide initial studies for the engineering of variant GCases and, potentially, molecular chaperones for therapeutic use.

Gaucher disease is a lysosomal storage disorder caused by deficient glucocerebrosidase activity. We have previously shown that the cellular activity of the most common Gaucher disease-associated glucocerebrosidase variant, N370S, is increased when patient-derived cells are cultured with the chemical chaperone N-nonyl-deoxynojirimycin. Chemical chaperones stabilize proteins against misfolding, enabling their trafficking from the endoplasmic reticulum. Herein, the generality of this therapeutic strategy is evaluated with other glucocerebrosidase variants and with additional candidate chemical chaperones. Improved chemical chaperones are identified for N370S glucocerebrosidase. Moreover, we demonstrate that G202R, a glucocerebrosidase variant that is known to be retained in the endoplasmic reticulum, is also amenable to chemical chaperoning. The L444P variant is not chaperoned by any of the active site-directed molecules tested, likely because this mutation destabilizes a domain distinct from the catalytic domain.

Gaucher disease (GD) is a disorder of glycosphinglipid metabolism caused by deficiency of lysosomal acid beta-glucosidase (GC), resulting in progressive deposition of glucosylceramide in macrophages. The glucose analogue, N-butyl-deoxynojirimycin (NB-DNJ, Miglustat), is an inhibitor of the ceramide-specific glucosyltransferase (CSG) which catalyzes the first step of glycosphingolipids biosynthesis and is currently approved for the oral treatment of type 1 GD. Using site-directed mutagenesis, we constructed plasmids containing wild-type and several mutations in glucocerebrosidase (GBA) gene. The plasmids were transfected into COS-7 cells and stable transfected cell lines were obtained by geneticin (G418) selection. Cells were cultured during 6 days with medium with or without 10 microM NB-DNJ. The addition of NB-DNJ to COS-7 cell medium leads to 1.3-, 2.1-, 2.3-, 3.6-, and 9.9-fold increase in the activity of S364R, wild-type, N370S, V15M, and M123T GC, respectively. However, no significant changes were observed in the activity of the L444P, L336P, and S465del mutated proteins, but a small decrease in the rare P266L variant was observed. These results suggest that NB-DNJ, in addition to the inhibitory effect on CSG, also works as a "chemical chaperone", increasing the activity of acid beta-glucosidase of wild-type and several GC mutated proteins, including the most frequent N370S mutation. The specific location of the Miglustat binding site in GC is unknown. Potential binding sites in the enzyme have been searched for using computational molecular docking. The searching strategy identified three potential GC binding sites for Miglustat, one being the substrate-binding site of the enzyme, which was the best-ranked site by AutoDock program. Therefore, it is possible that Miglustat exerts its chaperoning activity on acid beta-glucosidase by acting as an inhibitor bound at the active site. This increase on the activity of the acid beta-glucosidase would imply that Miglustat is not only a substrate reducer but also an inhibitor of the GC degradation, with very promising clinical implications for the treatment of GD patients.

We investigated 10 unrelated Chinese patients with type 2 Gaucher disease and performed ex vivo expression for the novel mutations to characterize their functional defects. These patients were diagnosed by enzymatic assays and clinicopathologic features over the past five years in a national centre in China. Genomic DNA was sequenced by a two-stage PCR approach for mutations in the functional GBA gene. Novel mutations were expressed with baculovirus-transfected Sf21 cells. Six novel mutations were found (in traditional nomenclature): P122L, Y363C, N382K, L383R, L385P, and M416V. Review of reported mutations indicated clustering of type 2 mutations in three regions of the GBA gene. Expression of novel mutations revealed that the enzyme defect could arise from one of two mechanisms: loss of catalytic activity (Y363C and M416V) or enzyme instability (P122L and N382K).