RESUMO
Transthyretin (TTR) is a tetrameric beta-sheet-rich protein that is important in the plasma transport of thyroxine and retinol. Mutations in the TTR gene cause TTR tetramer protein to dissociate to monomer, which is the rate-limiting step in familial amyloid polyneuropathy. Amyloidogenicity of individual TTR variants depends on the types of mutation that induce significant changes in biophysical, biochemical and/or biological properties. G101S TTR variant was previously identified in a Japanese male without amyloidotic symptom, and was considered as a non-amyloidogenic TTR variant. However, little is known about G101S TTR. Here, we found slight but possibly important biophysical differences between wild-type (WT) and G101S TTR. G101S TTR had slower rate of tetramer dissociation and lower propensity for amyloid fibril formation, especially at mild low pH (4.2 and 4.5), and was likely to have strong hydrophobic interaction among TTR monomers, suggesting relatively higher stability of G101S TTR compared with WT TTR. Cycloheximide (CHX)-based assay in HEK293 cells revealed that intracellular G101S TTR expression level was lower, but extracellular expression was higher than WT TTR, implying enhanced secretion efficiency of G101S TTR protein compared with WT TTR. Moreover, we found that STT3B-dependent posttranslational N-glycosylation at N98 residue occurred in G101S TTR but not in other TTR variants, possibly due to amino acid alterations that increase N-glycosylation preference or accelerate rigid structure formation susceptible to N-glycosylation. Taken together, our study characterizes G101S TTR as a stable and N-glycosylable TTR, which may be linked to its non-amyloidogenic characteristic.
Assuntos
Pré-Albumina/metabolismo , Amiloide/metabolismo , Neuropatias Amiloides Familiares , Glicosilação , Células HEK293 , Células HeLa , Hexosiltransferases/genética , Humanos , Proteínas de Membrana/genética , Pré-Albumina/genéticaRESUMO
We aimed to evaluate the effects of cytochrome P450 (CYP) 2C19 and CYP3A5 polymorphisms on zonisamide (ZNS) clearance. The pharmacokinetics of the 282 ZNS concentrations at a steady state obtained from 99 Japanese epileptic patients was performed with a nonlinear mixed-effect modeling program, using a one-compartment open pharmacokinetic model with first-order elimination. The covariates screened included the total body weight, gender, ZNS daily dose, CYP2C19 and CYP3A5 genotypes, and the coadministered antiepileptic drugs. The final model of ZNS apparent clearance was as follows: CL = 1.22 x (BW/44)0.77 x DOSE(-0.17 x 0.84CYP2C19 hetero EM x 0.70CYP2C19 PM x 1.24CBZ x 1.28PHT x 1.29PB x eetaCL where CL is the apparent oral clearance of ZNS, DOSE is ZNS daily dose, and CYP2C19 heterozygous extensive metabolizer (EM) or CYP2C19 poor metabolizer (PM) is equal to 1 if one or two CYP2C19-defective alleles are carried, respectively; otherwise, it is 0. Carbamazepine (CBZ), phenytoin (PHT), or phenobarbital (PB) is equal to 1 if carbamazepine, phenytoin, or phenobarbital is coadministered, respectively; otherwise, it is 0. etaCL is the independent random error distributed normally with the mean zero and variance equal to omegaCL. The CL of ZNS was lower in the CYP2C19 heterozygous extensive metabolizers and poor metabolizers than in the homozygous extensive metabolizers by 16% and 30%, respectively (P < 0.001). An effect of CYP3A5 polymorphisms was not identified. The coadministration of carbamazepine, phenytoin, or phenobarbital increased the CL of ZNS by 24% to 29%. This report demonstrates that the CYP2C19 genotype affects the ZNS metabolism in Japanese epileptic subjects. The clinical relevance of these changes remains to be explored in future studies.
Assuntos
Anticonvulsivantes/farmacocinética , Hidrocarboneto de Aril Hidroxilases/genética , Citocromo P-450 CYP3A/genética , Isoxazóis/farmacocinética , Adolescente , Adulto , Algoritmos , Hidrocarboneto de Aril Hidroxilases/metabolismo , Peso Corporal/fisiologia , Criança , Citocromo P-450 CYP2C19 , Citocromo P-450 CYP3A/metabolismo , Interações Medicamentosas , Feminino , Humanos , Japão , Masculino , Modelos Estatísticos , Polimorfismo Genético , População , Caracteres Sexuais , Adulto Jovem , ZonisamidaRESUMO
BACKGROUND: This study was designed to verify whether the glutathione S-transferase (GST) genotypes affect mild hepatotoxicity in valproic acid (VPA)-treated patients. METHODS: The association between the GSTM1 and GSTT1 genotypes, and the levels of aminotransferases and total bilirubin was retrospectively investigated in 149 Japanese epileptic patients treated with VPA. RESULTS: The adjusted odds ratio (OR) of the GSTM1- vs. GSTM1+ genotype and the GSTM1-/GSTT1-vs. GSTM1+/GSTT1+ genotypes for gamma-glutamyltransferase (GGT) increase over the upper limit of normal were 2.8 [95% confidence interval (CI): 1.1-7.2] and 6.5 (95% CI: 1.5-28.0), respectively. The GSTT1 genotypes alone did not significantly affect the liver function tests. The alanine aminotransferase, aspartate aminotransferase and (gamma-glutamyltransferase) GGT levels in patients treated with VPA >6 months were significantly higher in the GSTM1- than GSTM1+ genotype. The GGT levels were significantly higher in the older subjects receiving polytherapy, and the effects of the polytherapy and age were greater in the GSTM1- genotype. CONCLUSIONS: The GSTM1- and GSTM1-/GSTT1- genotypes may be a genetic risk factor for the increase of GGT in VPA-treated patients. However, it was not possible to clarify whether the GGT increase was caused by VPA-induced hepatotoxicity or not.
Assuntos
Anticonvulsivantes/uso terapêutico , Epilepsia/tratamento farmacológico , Glutationa Transferase/genética , Ácido Valproico/uso terapêutico , gama-Glutamiltransferase/sangue , Adolescente , Adulto , Criança , Epilepsia/enzimologia , Epilepsia/genética , Feminino , Genótipo , Humanos , Masculino , Fatores de RiscoRESUMO
A plausible explanation for many MHC-linked diseases is lacking. Sequencing of the MHC class I region (coding units or full contigs) in several human and nonhuman primate haplotypes allowed an analysis of single nucleotide variations (SNV) across this entire segment. This diversity was not evenly distributed. It was rather concentrated within two gene-rich clusters. These were each centered, but importantly not limited to, the antigen-presenting HLA-A and HLA-B/-C loci. Rapid evolution of MHC-I alleles, as evidenced by an unusually high number of haplotype-specific (hs) and hypervariable (hv) (which could not be traced to a single species or haplotype) SNVs within the classical MHC-I, seems to have not only hitchhiked alleles within nearby genes, but also hitchhiked deleterious mutations in these same unrelated loci. The overrepresentation of a fraction of these hvSNV (hv1SNV) along with hsSNV, as compared to those that appear to have been maintained throughout primate evolution (trans-species diversity; tsSNV; included within hv2SNV) tends to establish that the majority of the MHC polymorphism is de novo (species specific). This is most likely reminiscent of the fact that these hsSNV and hv1SNV have been selected in adaptation to the constantly evolving microbial antigenic repertoire.