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Background: Oculocutaneous albinism (OCA) is a congenital heterogeneous group of autosomal recessive disorders characterized by the absence or loss of melanin in the skin, eyes and hair of the affected individuals. Based on the mutated gene, OCA has been classified into eight sub-types (OCA1-8) with overlapping clinical phenotypes. Mutations in the TYR gene cause OCA1, the most prevalent OCA worldwide including India. Mutations in OCA2 and SLC45A2, both of which regulate melanosomal pH that is critical to TYR activity, cause OCA2 and OCA4 respectively, the other common OCA subtypes in India. Methods: In the present study, we have included 54 OCA-affected cases from 41 unrelated families representing 16 different marriage/ethnic groups from 17 districts of West Bengal, India. We pursued a PCR-sequencing based approach followed by bioinformatic analysis to identify mutations in TYR, OCA2 and SLC45A2 genes. Results: Mutations were detected in 27 of the 54 (50%) OCA patients from 18 unrelated families, representing 9 different marriage/ethnic groups from 11 districts of West Bengal. Three TYR variants: NM_000372.4: c.391 A > G, NP_000363.1: p. Lys131Glu; NM_000372.4: c.1037G > T; NP_000363.1: p. Gly346Val, NM_000372.4: c.715 C > T; NP_000363.1:p.Arg239Trp was identified for the first time in Eastern Indian OCA cases. A novel nonsense variant: NM_016180.5: c.389 T > A, NP_057264.4: p. Leu130* and a novel synonymous variation NM_016180.5: c.1092 A > G; NP_057264.4: p.364E = were identified in SLC45A2. Additionally, NM_016180.5: c.904A > T; NP_057264.4: p. Thre302Ser was identified for the first time in any Eastern Indian OCA case. We identified 2 previously reported mutations in OCA2. In concordance with previous reports, NM_000372.4: c.832C > T, NP_000363.1: p. (Arg278*) was the commonest TYR mutation. Conclusion: The results of our study enrich the mutational spectrum of the known OCA causing genes in Eastern India, which would facilitate accurate diagnosis, familial screening, carrier detection and containment of the disease load. [ABSTRACT FROM AUTHOR]

UVB exposure accelerates skin aging and pigmentation. Melatonin effectively regulates tyrosinase (TYR) activity and aging. The purpose of this study was to determine the association between premature senescence and pigmentation, and the mechanism of melanin synthesis effected by melatonin. Primary melanocytes were extracted and identified from the male foreskin. To inhibit TYR expression, primary melanocytes were transduced with the lentivirus pLKD-CMV-EGFP-2A-Puro-U6-TYR. The wild-type TYR(+/+) and TYR(–/–) or TYR(+/–) knockout C57BL/6 J mice were used to determine the role of TYR on melanin synthesis in vivo. Results showed that UVB-induced melanin synthesis is dependent on TYR in primary melanocytes and mice. Furthermore, in primary melanocytes pretreated with Nutlin-3 or PFT-α to up or downregulate p53, results showed that premature senescence and melanin synthesis increased in primary melanocytes after UVB irradiation at 80 mJ/cm2, and further increased after being treated with Nutlin-3, while significantly decreased with PFT-α. In addition, melatonin inhibited UVB-induced premature senescence associated with inactivation of p53 and phosphorylation of p53 on Ser15 (ser-15), a decrease of melanin synthesis accompanied by reduced TYR expression. Moreover, skin erythema and pigmentation induced by UVB were reduced in the dorsal and ear skin of mice topically pretreated with 2.5% melatonin. These indicate that melatonin inhibits UVB-induced senescence-associated pigmentation via the p53-TYR pathway in primary melanocytes and prevents pigmentation obviously in the dorsal and ear skin of C57BL/6 J mice after UVB irradiation. Key messages: P53 links UVB irradiation-induced senescence and senescence-associated pigmentation and regulates TYR in primary melanocytes after UVB irradiation. Melatonin inhibits senescence-associated pigmentation through the p53-TYR pathway in primary melanocytes. Melatonin prevents skin erythema and melanin pigmentation induced by UVB irradiation in the dorsal and ear skin of C57BL/6J mice. [ABSTRACT FROM AUTHOR]

Albinism is a heterogeneous group of genetically determined diseases associated with complete or partial disruption of melanin synthesis. There are various forms of hereditary albinism, including oculocutaneous albinism, ocular albinism, and different syndromic forms. The study analyzed a sample of patients (n = 90) with varied forms of albinism for the presence of pathogenic variants of the nucleotide sequence in the TYR gene as the most common cause of type 1 oculocutaneous albinism (OCA1). This clinical and genetic form was found in 32 patients. On the basis of the results obtained, we examined the spectrum and frequency of variants in the TYR gene. Also, we described the clinical signs that are most common among patients, as well as clinical features atypical of this disease. [ABSTRACT FROM AUTHOR]

The widely recognized color polymorphisms of molluscan shell have been appreciated for hundreds of years by collectors and scientists, while molecular mechanisms underlying shell pigmentation are still poorly understood. Tyrosinase is a key rate–limiting enzyme for the biosynthesis of melanin. Here, we performed an extensive multi-omics data mining and identified two tyrosinase genes, including tyrosinase and tyrosinase-like protein 2 (Tyr and Typ-2 respectively), in the Pacific oyster Crassostrea gigas, and investigated the expression patterns of tyrosinase during adults and embryogenesis in black and white shell color C. gigas. Tissue expression analysis showed that two tyrosinase genes were both specifically expressed in the mantle, and the expression levels of Tyr and Typ-2 in the edge mantle were significantly higher than that in the central mantle. Besides, Tyr and Typ-2 genes were black shell-specific compared with white shell oysters. In situ hybridization showed that strong signals for Tyr were detected in the inner surface of the outer fold, whereas positive signals for Typ-2 were mainly localized in the outer surface of the outer fold. In the embryos and larvae, the high expression of Tyr mRNA was detected in eyed-larvae, while Typ-2 mRNA was mainly expressed at the trochophore and early D-veliger. Furthermore, the tyrosinase activity in the edge mantle was significantly higher than that in the central mantle. These findings indicated that Tyr gene may be involved in shell pigmentation, and Typ-2 is more likely to play critical roles not only in the formation of shell prismatic layer but also in shell pigmentation. In particular, Typ-2 gene was likely to involve in the initial non-calcified shell of trochophores. The work provides valuable information for the molecular mechanism study of shell formation and pigmentation in C. gigas. [ABSTRACT FROM AUTHOR]

Using the method of adsorption spectroscopy, the temperature dependence of the electronic absorption spectra of the fluorescent chemosensor (CS), based on the supramolecular pyrene-2β-cyclodextrin complex (Pyr@2βCD, PCD), was studied in the absence and in the presence of phenylalanine (Phe). The application of CS, where pyrene serves as a fluorescent probe, is based on the ability of CS to form the inclusion complexes with small organic molecules as well as with aromatic amino acids (AA) such as Phe, tryptophan (Trp), tyrosine (Tyr), and histidine (His) in aqueous solutions. Upon heating to 55 °C, the PCD complex in the presence of Phe shows a higher stability as compared to that in the absence of Phe. The molecular dynamics simulation was applied to study the thermal stability of PCD and its complexes with the above AAs in water. The PCD complex exists in two configurations. In configuration 1 the planar Pyr molecule lies in the equatorial plane of the βCD dimer, the plane of Pyr is nearly perpendicular to the vertical axis of the dimer 2βCD, and water fills up the empty part of the cavity. In configuration 2, the plane of Pyr is inclined with respect to the axis of the 2βCD dimer by ~30°. The PCD complex initially prepared in state 1 is spontaneously transformed into state 2 and remains stable up to the boiling temperature. The transition of PCD from the form 1 to 2 is provided by fluctuations in water content in its cavities. The inclusion complexes of amino acids 2AA@PCD exist in a single conformation 1. Complexes of PCD with Trp and Phe are stable up to the boiling temperature, i.e., these AAs are preserved within the PCD cavities even at the elevated temperature. The complex with Tyr decays at 60 °C, and the complex with His is unstable at room temperature and above. [ABSTRACT FROM AUTHOR]

Oil extraction from the kernels of Argania spinosa (L.) Skeels (Sapotaceae), an endemic tree of Morocco, produces argan press-cake (APC) used as a shampoo and to treat sprains, scabies, and for healing wounds. We have previously reported that argan oil has antimelanogenesis effect. Here, we determined if the by-product, APC, has melanogenesis regulatory effect using B16 murine melanoma cells. The effect of APC ethanol extract on cell proliferation and melanin content of B16 cells were measured, and to elucidate the mechanism involved, the expression level of melanogenic enzymes tyrosinase (TYR), dopachrome tautomerase (DCT), and tyrosinase-related protein 1 (TRP1) were determined and mRNA expression level of microphthalmia- associated transcription factor (Mitf) and Tyr genes were quantified. APC ethanol extract showed a significant melanin biosynthesis inhibitory effect on B16 cells in a time-dependent manner without cytotoxicity, which could be due to the decreased expression of TYR, TRP1, and DCT in a time-dependent manner. APC extract down regulated Mitf and Tyr. Decreased TRP1 and DCT levels could be due to post-translational modifications. These results suggest that APC extract may be used as a new source of natural whitening products and may be introduced as an important pharmacological agent for the treatment of hyperpigmentation disorders. [ABSTRACT FROM AUTHOR]

Protein-based particles are very promising colloidal systems for protection and controlled release applications in the food, cosmetics and pharmaceutical sector. One technique to produce these protein colloidal particles is liquid antisolvent precipitation (LAS). Despite the simplicity and versatility of LAS, not much is known about the protein conformational changes and interactions that are at the basis of the particle formation process. In this study, steady state fluorescence experiments using intrinsic fluorophores were evaluated as a tool to unravel the dynamics of the protein nanoparticle formation. Colloidal whey protein isolate and gliadin particles were produced by LAS. Changes in particle diameter (distribution), polydispersity index and photophysical properties of intrinsic fluorophores were monitored as a function of antisolvent concentration. By combining dynamic light scattering with photophysical data, a model of the changes occurring during particle formation and disintegration could be proposed. The results suggest that particle formation and disintegration are fully reversible processes during which the main changes in protein conformation (around the fluorescent probes) occur at the same antisolvent concentrations. In principle, steady state fluorescence measurements using intrinsic probes can indeed be used to effectively report on (part of the) conformational changes for both protein systems under study. [ABSTRACT FROM AUTHOR]

From the slim dossier of mythological lore concerning the senior Norse god Týr, which includes Loki's mockery in Lokasenna, a single myth emerges: his binding of the wolf Fenrir and concurrent loss of his sword and oath-taking hand in the wolf's maw. A Norse model of the surrender of a body part in return for enhanced psycho-somatic ability in a divine meta-function, as seen in Óðinn's pawning of an eye for knowledge, is extended to Týr, whose compensatory gain is skill in bold and clever power politics: knowledge of the social and legal systems, and their artful manipulation. The economy of loss and gain is measured against the events of the ultimate battle of Ragnarǫk, in which the loosed Fenrir kills Óðinn and Garmr, dog or wolf, and Týr kill one another. [ABSTRACT FROM AUTHOR]

Purpose: To perform molecular analysis of five Korean patients with oculocutaneous albinism (OCA) and review the clinical and genetic characteristics of 21 Korean OCA patients. Methods: TYR, OCA2 and SLC45A2 were analyzed by direct DNA sequencing in five unrelated OCA patients who received thorough ophthalmic evaluation. Results: We identified three different TYR mutations in three patients (c.929dupC, R278X, and R52I), among which the latter two had been previously reported in other populations, but are reported here for the first time in a Korean context. In one patient we identified two different mutations of OCA2 [c.1784+1G>A and c.1842G>T (K614N)]. One patient was confirmed to have OCA4 by detecting two SLC45A2 mutations [c.469G>A (D157N) and c.686G>A (C229Y)]. OCA1A (66.7%) was the most common subtype in 21 Korean albinism patients, and 70% of patients were heterozygotes for 2 different mutational alleles. c.929dupC (54.8%) and R77Q (16.1%) were the most frequent mutational alleles of TYR in Koreans. Conclusions: Three mutational alleles, R278X and R52I of the TYR gene and C229Y of the SLC45A2 gene, are added to the mutational spectra of Korean patients with OCA, and we report the first Korean case of OCA2 with the OCA2 gene mutations. [ABSTRACT FROM AUTHOR]

The present study aims to investigate the mechanism of CaM kinase IV activation during hypoxia and tests the hypothesis that hypoxia-induced increased activity of CaM kinase IV is due to Src kinase mediated increased tyrosine phosphorylation of calmodulin and CaM kinase IV in neuronal nuclei of the cerebral cortex of newborn piglets. Piglets were divided into normoxic (Nx, n = 5), hypoxic (Hx, FO of 0.07 for 1 h, n = 5) and hypoxic-pretreated with Src kinase inhibitor PP2 (Hx-Srci, n = 5) groups. Src inhibitor was administered (1.0 mg/kg, I.V.) 30 min prior to hypoxia. Neuronal nuclei were isolated and purified, and tyrosine phosphorylation of calmodulin (Tyr) and CaM kinase IV determined by Western blot using anti-phospho-(pTyr)-calmodulin, anti-pTyrosine and anti-CaM kinase IV antibodies. The activity of CaM kinase IV and its consequence the phosphorylation of CREB protein at Ser were determined. Hypoxia resulted in increased tyrosine phosphorylation of calmodulin at Tyr, tyrosine phosphorylation of CaM kinase IV, activity of CaM kinase IV and phosphorylation of CREB protein at Ser. The data show that administration of Src kinase inhibitor PP2 prevented the hypoxia-induced increased tyrosine phosphorylation of calmodulin (Tyr) and tyrosine phosphorylation of CaM.kinase IV as well as the activity of CaM kinase IV and CREB phosphorylation at Ser. We conclude that the mechanism of hypoxia-induced increased activation of CaM kinase IV is mediated by Src kinase-dependent tyrosine phosphorylation of the enzyme and its activator calmodulin. We propose that Tyr phosphorylated calmodulin, as compared to non-phosphorylated, binds with a higher affinity at the calmodulin binding site (rich in basic amino acids) of CaM kinase IV leading to increased activation of CaM kinase IV. Similarly, tyrosine phosphorylated CaM kinase IV binds its substrate with a higher affinity and thus increased tyrosine phosphorylation leads to increased activation of CaM kinase IV resulting in increased CREB phosphorylation that triggers increased transcription of proapoptotic proteins that initiate hypoxic neuronal death. [ABSTRACT FROM AUTHOR]

The mobility of βCH2 moieties in oxidized and reduced cytochrome b5 was studied by analyzing the 13C relaxation of the J-split components, in terms of C-H dipole–C-H dipole cross correlation rates. A 2D 13C-1H experiment is proposed to measure these rates that provide the internal effective reorientation correlation time for each CH2 moiety. It is found that higher mobility is present in the α helices forming the heme pocket. On the contrary, the β strands, which form the hydrophobic core of the molecule, have the lowest mobility. The general pattern is the same for the oxidized and reduced species, indicating that any oxidation-dependent property detected for backbone NH moieties does not affect the CH2 mobility. [ABSTRACT FROM AUTHOR]