Genotype-Structure-Phenotype Correlations of Disease-Associated IGF1R Variants and Similarities to Those of INSR Variants.

We previously reported genotype-phenotype correlations in 12 missense variants causing severe insulin resistance, located in the second and third fibronectin type III (FnIII) domains of the insulin receptor (INSR), containing the α-β cleavage and part of insulin-binding sites. This study aimed to identify genotype-phenotype correlations in FnIII domain variants of IGF1R, a structurally related homolog of INSR, which may be associated with growth retardation, using the recently reported crystal structures of IGF1R. A structural bioinformatics analysis of five previously reported disease-associated heterozygous missense variants and a likely benign variant in the FnIII domains of IGF1R predicted that the disease-associated variants would severely impair the hydrophobic core formation and stability of the FnIII domains or affect the α-β cleavage site, while the likely benign variant would not affect the folding of the domains.

Clinical usefulness of multigene screening with phenotype-driven bioinformatics analysis for the diagnosis of patients with monogenic diabetes or severe insulin resistance.

Aims: Monogenic diabetes is clinically heterogeneous and differs from common forms of diabetes (type 1 and 2). We aimed to investigate the clinical usefulness of a comprehensive genetic testing system, comprised of targeted next-generation sequencing (NGS) with phenotype-driven bioinformatics analysis in patients with monogenic diabetes, which uses patient genotypic and phenotypic data to prioritize potentially causal variants.

Methods: We performed targeted NGS of 383 genes associated with monogenic diabetes or common forms of diabetes in 13 Japanese patients with suspected (n = 10) or previously diagnosed (n = 3) monogenic diabetes or severe insulin resistance.

A variant in the gene in a family with occult macular dystrophy in a predicted intrinsically disordered region.

Significance: The responsible genetic variants for occult macular dystrophy (OMD) were found at the predicted intrinsically disordered region (IDR) of the gene.

Purpose: We examined the phenotypes and genotypes of family members from OMD. In addition, the genetic characteristics of the gene in OMD were investigated.

Esterification of side-chain oxysterols by lysosomal phospholipase A2.

Side-chain oxysterols produced from cholesterol either enzymatically or non-enzymatically show various bioactivities. Lecithin-cholesterol acyltransferase (LCAT) esterifies the C3-hydroxyl group of these sterols as well as cholesterol. Lysosomal phospholipase A2 (LPLA2) is related to LCAT but does not catalyze esterification of cholesterol.

Structural modeling and mutagenesis of endo-β-N-acetylglucosaminidase from Ogataea minuta identifies the importance of Trp295 for hydrolytic activity.

Endo-β-N-acetylglucosaminidase from the methylotrophic yeast Ogataea minuta (Endo-Om) is a glycoside hydrolase family 85 enzyme that has dual catalytic activity in the hydrolysis and transglycosylation of complex N-glycans, in common with the enzymes from the eukaryotic species. In this study, we have conducted mutagenesis of Endo-Om at Trp295, to determine the effect on hydrolytic activity. Structural modeling predicted that Trp295 forms an important interaction with the α-1,3-linked mannose residue of the trimannosyl N-glycan core, rather than being directly involved in catalytic activity.

Inhibitory effects and specificity of synthetic sialyldendrimers toward recombinant human cytosolic sialidase 2 (NEU2).

Human sialidase 2 (NEU2) is a cytoplasmic sialidase that degrades sialylglycoconjugates, including glycoproteins and gangliosides, via hydrolysis of terminal sialic acids to produce asialo-type molecules. Here, we first report the inhibitory effects of a series of synthetic sialyldendrimers comprising three types [Dumbbell(1)6-S-Neu5Ac(6), Fan(0)3-S-Neu5Ac(3) and Ball(0)4-S-NeuAc(4)] toward recombinant human NEU2 in vitro. Among them, Dumbbell(1)6-S-Neu5Ac(6) exhibited the most potent inhibitory activity (concentration causing 50% inhibition (IC(50)), 0.

Introduction of an N-glycan sequon into HEXA enhances human beta-hexosaminidase cellular uptake in a model of Sandhoff disease.

Human lysosomal beta-hexosaminidase A is a heterodimer composed of alpha- and beta-subunits encoded by HEXA and HEXB, respectively. We genetically introduced an additional N-glycosylation sequon into HEXA, which caused amino acid substitutions (S51 to N and A53 to T) at homologous positions to N84 and T86 in the beta-subunit. The mutant HexA (NgHexA) obtained from a Chinese hamster ovary (CHO) cell line co-expressing the mutated HEXA and wild-type HEXB complementary DNAs was demonstrated to contain an additional mannose-6-phosphate (M6P)-type-N-glycan.

Binding parameters and thermodynamics of the interaction of imino sugars with a recombinant human acid alpha-glucosidase (alglucosidase alfa): insight into the complex formation mechanism.

Background: Recently, enzyme enhancement therapy (EET) for Pompe disease involving imino sugars, which act as potential inhibitors of acid alpha-glucosidases in vitro, to improve the stability and/or transportation of mutant acid alpha-glucosidases in cells was studied and attracted interest. However, the mechanism underlying the molecular interaction between the imino sugars and the enzyme has not been clarified yet.

Methods: We examined the inhibitory and binding effects of four imino sugars on a recombinant human acid alpha-glucosidase, alglucosidase alfa, by means of inhibition assaying and isothermal titration calorimetry (ITC).

Phosphorylation-induced conformational switching of CPI-17 produces a potent myosin phosphatase inhibitor.

Phosphorylation of endogenous inhibitor proteins for type-1 Ser/Thr phosphatase (PP1) provides a mechanism for reciprocal coordination of kinase and phosphatase activities. A myosin phosphatase inhibitor protein CPI-17 is phosphorylated at Thr38 through G-protein-mediated signals, resulting in a >1000-fold increase in inhibitory potency. We show here the solution NMR structure of phospho-T38-CPI-17 with rmsd of 0.

Structural and biochemical studies on Pompe disease and a "pseudodeficiency of acid alpha-glucosidase".

We constructed structural models of the catalytic domain and the surrounding region of human wild-type acid alpha-glucosidase and the enzyme with amino acid substitutions by means of homology modeling, and examined whether the amino acid replacements caused structural and biochemical changes in the enzyme proteins. Missense mutations including p.R600C, p.

Molecular pathologies of and enzyme replacement therapies for lysosomal diseases.

Lysosomal diseases comprise a group of inherited disorders resulting from defects of lysosomal enzymes and their cofactors, and in many of them the nervous system is affected. Recently, enzyme replacement therapy with recombinant lysosomal enzymes has been clinically available for several lysosomal diseases. Such enzyme replacement therapies can improve non-neurological disorders but is not effective for neurological ones.

Prediction of the mechanism of action of omuralide (clasto-lactacystin beta-lactone) on human cathepsin A based on a structural model of the yeast proteasome beta5/PRE2-subunit/omuralide complex.

Cathepsin A (CathA) is a lysosomal serine carboxypeptidase that exhibits homology and structural similarity to the yeast and wheat serine carboxypeptidases (CPY and CPW) belonging to the alpha/beta-hydrolase fold family. Human CathA (hCathA) and CPW have been demonstrated to be inhibited by a proteasome (threonine protease) inhibitor, lactacystin, and its active derivative, omuralide (clasto-lactacystin beta-lactone), as well as chymostatin. A hCathA/omuralide complex model constructed on the basis of the X-ray crystal structures of the CPW/chymostatin complex and the yeast proteasome beta-subunit (beta5/PRE2)/omuralide one predicted that the conformation of omuralide in the active-site cleft of proteasome beta5/PRE2 should be very similar to that of chymostatin at the S1 catalytic subsites in the hCathA- and CPW-complexes.

Fabry disease: correlation between structural changes in alpha-galactosidase, and clinical and biochemical phenotypes.

Fabry disease comprises classic and variant phenotypes. The former needs early enzyme replacement therapy, and galactose infusion is effective for some variant cases. Attempts of early diagnosis before manifestations appear will begin in the near future.

Structural and immunocytochemical studies on alpha-N-acetylgalactosaminidase deficiency (Schindler/Kanzaki disease).

Alpha-N-acetylgalactosaminidase (alpha-NAGA) deficiency (Schindler/Kanzaki disease) is a clinically and pathologically heterogeneous genetic disease with a wide spectrum including an early onset neuroaxonal dystrophy (Schindler disease) and late onset angiokeratoma corporis diffusum (Kanzaki disease). In alpha-NAGA deficiency, there are discrepancies between the genotype and phenotype, and also between urinary excretion products (sialyl glycoconjugates) and a theoretical accumulated material (Tn-antigen; Gal NAcalpha1-O-Ser/Thr) resulting from a defect in alpha-NAGA. As for the former issue, previously reported genetic, biochemical and pathological data raise the question whether or not E325K mutation found in Schindler disease patients really leads to the severe phenotype of alpha-NAGA deficiency.

Structural basis of the GM2 gangliosidosis B variant.

To study the structural basis of the GM2 gangliosidosis B variant, we constructed the three-dimensional structures of the human beta-hexosaminidase alpha-subunit and the heterodimer of the alpha- and beta-subunits, Hex A, by homology modeling. The alpha-subunit is composed of two domains, domains I and II. Nine mutant models due to specific missense mutations were constructed as well and compared with the wild type to determine structural defects.

Molecular and structural studies of the GM2 gangliosidosis 0 variant.

To determine the molecular basis of the GM2 gangliosidosis 0 variant, we constructed a three-dimensional structure of the human beta-hexosaminidase beta-subunit by homology modeling. It is composed of two domains, domains I and II, and has three disulfide bonds. C534 is located on an extra helix in domain II and forms a disulfide bond with C551.