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Glutamine Synthetase 1 (GS1) is a key enzyme that catalyzes the ATP-dependent synthesis of l-glutamine from l-glutamate and is also member of the Glutamate Glutamine Cycle, a complex physiological process between glia and neurons that controls glutamate homeostasis and is often found compromised in neurodegenerative diseases including Huntington&rsquo, s disease (HD). Here we report that the expression of GS1 in neurons ameliorates the motility defects induced by the expression of the mutant Htt, using a Drosophila model for HD. This phenotype is associated with the ability of GS1 to favor the autophagy that we associate with the presence of reduced Htt toxic protein aggregates in neurons expressing mutant Htt. Expression of GS1 prevents the TOR activation and phosphorylation of S6K, a mechanism that we associate with the reduced levels of essential amino acids, particularly of arginine and asparagine important for TOR activation. This study reveals a novel function for GS1 to ameliorate neuronal survival by changing amino acids&rsquo, levels that induce a &ldquo, starvation-like&rdquo, condition responsible to induce autophagy. The identification of novel targets that inhibit TOR in neurons is of particular interest for the beneficial role that autophagy has in preserving physiological neuronal health and in the mechanisms that eliminate the formation of toxic aggregates in proteinopathies.

Glutamine Synthetase 1 (GS1) is a key enzyme that catalyzes the ATP-dependent synthesis of l-glutamine from l-glutamate and is also member of the Glutamate Glutamine Cycle, a complex physiological process between glia and neurons that controls glutamate homeostasis and is often found compromised in neurodegenerative diseases including Huntington's disease (HD). Here we report that the expression of GS1 in neurons ameliorates the motility defects induced by the expression of the mutant Htt, using a

Glutamine Synthetase1 (GS1) is an enzyme that catalyzes the ATP-dependent synthesis of L-glutamine from L-glutamate and ammonia as a key element of the glutamate glutamine cycle, a complex physiological process occurring between glia and neurons, necessary to control the homeostasis of glutamate. Using a Drosophila model for Huntington’s disease, we report that expression of GS1 in neurons ameliorates the motility defects of animals expressing the mutant Httex1-Q93 form of the huntingtin gene. At the cellular level, expression of GS1 increases the basal level of autophagy and significantly reduces the size of the toxic Htt-Q93 protein aggregates. In addition, we found that expression of GS1 prevents TOR localization at the lysosomal membrane and reduction in the phosphorylation of its effector S6K. This study reveals a novel function for GS1 in neurons linking its activity to the inhibition of TOR signaling and autophagy. The identification of novel pharmacological regulators of autophagy is of particular interest considering its beneficial role in controlling neuronal health and counteracting the detrimental effects of toxic aggregates of proteinopathies including Huntington’s disease.

Background aims In attempting to develop new strategies to circumvent the immunosuppression associated with glioblastoma (GB), novel approaches have been designed using dendritic cell (DC)-based vaccination, which is considered a promising strategy to attack high-grade glioma. In previous studies, we demonstrated that human mesenchymal stromal cells without genetic manipulation but primed with Paclitaxel (PTX) acquire a potent anti-tumor activity, providing an interesting new biological approach for drug delivery. On the basis of these results, we here investigated whether both CD14+ and their derived DCs may behave like mesenchymal stromal cells acquiring anti-tumor activity on priming with PTX. Methods Human CD14+ cells were isolated from peripheral blood. Fluorescence-activated cell sorter analysis was performed to determine the purity of CD14+ and their differentiation into mature DCs. Cells were primed by incubation with 1 μg/mL of PTX for 24 h, and the PTX released by cells was assessed by mass spectrometry analysis. Anti-tumor activity was checked by testing the conditioned medium (CM) on the proliferation of U87 MG, a GB cell line. Results Both CD14+ and DCs were able to incorporate PTX and release the drug in the CM in a time-dependent manner (maximal release over 24 h). The addition of CM from CD14+ and DCs loaded with PTX strongly inhibits proliferation of U87 MG cells. Conclusions Our results are the first demonstration that peripheral blood–derived CD14+ and DCs, in addition to their application for immunotherapy for GB, could also be used to delivery anti-cancer drugs, such as PTX, to kill GB cells.

Adult Refsum disease (ARD) is a progressive multisystem disorder that is characterized by retinitis pigmentosa, hearing and smell loss, skeletal deformities, and elevated levels of phytanic acid (PA) in tissues. Peripheral neuropathy, cardiac abnormalities, and skin ichthyosis are considered subsequent manifestations, and are often described in patients not treated with PA dietary restriction. Mutations of the gene encoding the phytanoyl-coenzyme A (CoA) hydroxylase enzyme (PHYH) are the major genetic cause of ARD,1 and in a small number of cases a second gene, PEX7, which encodes peroxin 7 receptor protein (PEX7), has been associated with the ARD phenotype.2 We observed two Italian siblings who presented with late-onset progressive ataxia and cognitive decline. They comprised a 56-year-old woman and her 63-year-old brother, born from consanguineous parents, and presented with infantile bilateral cataract and retinitis pigmentosa. Except for the visual defect, both siblings exhibited normal psychomotor development. In adulthood (at age 40 years for the brother and 53 years for the sister), both patients manifested progressive behavioral and cognitive abnormalities associated with ataxic gait. At the latest examination, at ages 57 and 63 years, respectively, they presented with dementia (Mini-Mental State Examination scores of 19/30 and 13/30, respectively), motor apraxia, ophthalmoparesis, mild dysarthria, ataxic gait, mild limb dysmetria, Babinski sign, and decreased lower-limb deep-tendon reflexes. Neither of the patients had hearing loss, anosmia, or short metacarpals/metatarsals, and only the brother presented with dilated cardiomyopathy. Brain MRI revealed mild diffuse atrophy, and muscle biopsy sampling revealed normal morphology. Nerve conduction studies demonstrated a mild motor demyelinating neuropathy in the lower limbs, and somatosensory evoked potentials revealed a prolongation of the central conduction time. Both patients also presented with increased plasma PA levels (387.5 and 188.9 µmol/L), suggesting a diagnosis of ARD. Mutational screening of PHYH was negative, but there was a novel homozygous mutation in PEX7, p.Leu12Pro, caused by a T>C transition at nucleotide 35 (c.35T>C). This missense variation involved a well-conserved residue, and has not been reported as a single-nucleotide polymorphism (SNP) in the Human Gene Mutation Database, National Center for Biotechnology Information database for SNPs (dbSNP132ver) or Exome Variant Server. In silico analyses predicted the mutation as probably damaging: the scores were 0.98 (PolyPhen-2-HumDiv), 0.635 (PolyPhen-2-HumVar), and 0 (Sorting Tolerant From Intolerant). The parents were not available for segregation analysis, and an asymptomatic brother was found to be heterozygous for this mutation. The patients refused a skin biopsy procedure, preventing investigations of plasmalogen synthesis.3 PEX7 mutations are most frequently found in infants affected by rhizomelic chondrodysplasia punctata type 1 (RCDP1), a congenital and rapidly worsening syndrome that is characterized by rhizomelia, chondrodysplasia punctata, cataract, and severe growth and mental retardation.3 The protein encoded by PEX7, Pex7, is essential for peroxisomal delivery of matrix enzymes containing the peroxisomal targeting signal type 2 in the amino acid sequence, including the phytanoyl-CoA hydroxylase and the plasmalogen synthesis apparatus.4 In both RCDP1 and ARD, patients present with elevated PA levels due to either a defect in the peroxisomal import of the metabolic enzymes or a primary loss-of-function of the phytanoyl-CoA hydroxylase enzyme.4 Several PEX7 mutations have so far been described in association with the RCDP1 phenotype. Only eight patients with PEX7 mutations and the Refsum phenotype have been reported, and in all of these cases the presentation was consistent with the ARD phenotype with a mild disease course (Table 1).2,3,5 In the previously reported cases, the most frequent disease manifestations were retinopathy, cataract, anosmia, hearing loss, and neuropathy (Table 1). In the cases described herein, the ocular abnormalities were also the earliest signs, but neither anosmia nor deafness was observed, while in the fifth decade both siblings developed progressive signs of dementia and ataxia. It is known that the clinical severity of this disease is associated with the residual activities and reduced amounts of Pex7.3 In particular, functional and modeling analyses have demonstrated that missense mutations associated with a severe phenotype are located in within the β sheets, probably causing a disruption of the protein structure.3 The p.Leu12Pro mutation, unlike previous missense mutations, is not located on the WD-40 repeat motif in PEX7, and it can be hypothesized that a less adverse effect on protein structure-allowing correct folding and greater residual activity-can account for the mild phenotype in these two patients. Table 1 Clinical, biochemical, and genetic characteristics of the patients with PEX7 gene mutations associated with Refsum disease phenotype, including the cases described in this study and review of the literature