Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We identified a heterozygous missense mutation that substituted aspartic acid (GAC) for alanine (GCC) at codon 1048 of the insulin receptor gene in a patient who displayed typical symptoms of Type A syndrome of insulin resistance. The proband's mother and younger brother were also found to be heterozygous for the mutation. We constructed the identified mutant insulin receptor cDNA by site-directed mutagenesis, transfected the mutant cDNA into COS 7 cells, and found that kinase activity of the mutant insulin receptors was markedly impaired. Ala1048 is located in the kinase domain of the insulin receptor beta-subunit and is conserved in most of protein-tyrosine kinases. Besides, neighboring Glu1047 is invariant in all protein kinases and is thought to be involved in interaction with ATP. Photoaffinity labeling of the mutant insulin receptor with ATP analogue, 8-azido (alpha-32P)ATP was not influenced by the mutation, suggesting that the mutation did not inhibit ATP binding but possibly interfered with subsequent phosphoryl transfer. Insulin-stimulated phosphorylation of exogenous substrate by partially purified insulin receptors prepared from COS 7 cells that were cotransfected with wild-type and mutant insulin receptor cDNAs was markedly impaired, whereas autophosphorylation was decreased by approximately 50% of wild-type receptors. These results indicated that the identified heterozygous substitution of Asp for Ala1048 in insulin receptor was responsible for insulin resistance of this patient.
Diabetes 1993 Dec
PMID:Ala1048-->Asp mutation in the kinase domain of insulin receptor causes defective kinase activity and insulin resistance. 824 30

A proband with chylomicronemia, pancreatitis, and non-insulin-dependent diabetes (NIDDM) bears two different mutations in exon 3 of the lipoprotein lipase (LPL) gene: a missense mutation, 75Arg-->Ser, inherited through the paternal line and a truncation, 73Tyr-->Ter, through the maternal line. NIDDM appeared to be independently segregating. The R75S mutant was studied in extracts and media from transfected COS-1 cells. Detectable amounts of catalytically competent R75S LPL suggested destabilization of the active homodimer as with exon 5 mutants (Hata et al. 1992. J. Biol. Chem. 267:20132-20139). Hydrolysis of a short-chain fatty acid ester indicated that R75S does not directly affect activation of LPL by apoC-II. Subjects with NIDDM and wild-type LPL, and nondiabetic middle-aged carriers of the 73Tyr-->Ter truncation had moderate hypertriglyceridemia (260-521 mg/dl) and reduced high density lipoprotein cholesterol. A maternal aunt with NIDDM carried the truncation. Her phenotype (triglycerides of 5,300 mg/dl, eruptive xanthomatosis, and recurrent pancreatitis) was as severe as that in homozygotes or compound heterozygotes. We conclude: (a) diabetic carriers of dysfunctional LPL alleles are at risk for severe lipemia; and (b) the physiologic defects in NIDDM may be additive or synergistic with heterozygous LPL deficiency.
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PMID:Mutations in exon 3 of the lipoprotein lipase gene segregating in a family with hypertriglyceridemia, pancreatitis, and non-insulin-dependent diabetes. 832 86

Glutamic acid decarboxylase (GAD) is the enzyme responsible for synthesis of the neurotransmitter gamma-aminobutyric acid in neurons and pancreatic beta cells. It is represented by two isoforms, GAD-65 and GAD-67, which are the products of two different genes and differ substantially only at their N-terminal regions. GAD-65 is a dominant autoantigen in stiff-man syndrome and insulin-dependent diabetes mellitus. In neurons and beta cells, GAD is concentrated around synaptic vesicles and synaptic-like microvesicles, respectively, as well as in the area of the Golgi complex. The mechanisms responsible for specific targeting of GAD to these organelles are not yet understood. The elucidation of the mechanism of subcellular targeting of GAD may be relevant to understanding its role as an autoantigen. In this study, the cloned genes for GAD-65 and GAD-67 were expressed separately in Chinese hamster ovary (CHO) cells and COS cells. While GAD-67 had a diffuse cytoplasmic localization, GAD-65 had a punctate distribution, with most of the immunoreactivity being concentrated in the area of the Golgi complex. A chimeric protein in which the 88 N-terminal amino acids of GAD-67 were replaced by the 83 N-terminal amino acids of GAD-65 was targeted to the Golgi complex, indicating that the N-terminal region of GAD-65 contains a targeting signal sufficient for directing the remaining portion of the molecule, highly similar in GAD-65 and GAD-67, to the Golgi complex-associated structures.
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PMID:Association of GAD-65, but not of GAD-67, with the Golgi complex of transfected Chinese hamster ovary cells mediated by the N-terminal region. 846 26

Plasmids containing cDNA for the rat 67- and 65-kD isoforms of glutamate decarboxylase (GAD-67 and GAD-65) were expressed in COS-cells, and lysates of [35S]methionine-labeled cells were used for immunoprecipitations. Sera from 38 patients with type 1 (insulin-dependent) diabetes mellitus, which precipitated a 64-kD antigen from rat islets, reacted with recombinant GAD-65 in relation to their anti-64-kD titers. The eight strongest sera also precipitated recombinant GAD-67, suggesting that certain epitopes are common to both isoforms. Subsequently, [35S]methionine-labeled GAD-65 was purified from COS cell lysates and employed in a binding assay with 50 sera of patients with recent onset of type 1 diabetes mellitus. 38 sera (76%) precipitated labeled GAD-65 with titers that correlated with islet cell antibodies (ICA), determined in a standard immunofluorescence assay. 2 sera were GAD positive but ICA negative, 4 were positive only for ICA, and 6 were negative for both GAD and ICA, as were the sera of 20 controls. The data illustrate that antibodies against GAD-65 are present in a majority of patients with type 1 diabetes mellitus and that autoantibodies against other islet cell antigens also exist. The radioligand-binding assay, which is convenient and sensitive for detecting GAD antibodies, will facilitate the screening of individuals with autoimmune islet cell disease.
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PMID:Demonstration of GAD-65 as the main immunogenic isoform of glutamate decarboxylase in type 1 diabetes and determination of autoantibodies using a radioligand produced by eukaryotic expression. 848 75

Two N-linked sites of glycosylation in the insulin receptor were examined for their contribution to insulin binding, tyrosine kinase activity, and receptor biosynthesis. Asn397 and Asn418 were replaced by Gln using site-directed mutagenesis either as single mutations, i.e., Q-397 and Q-418, or as a double mutation in which both sites were removed (Q-D). The mutations were transiently expressed in COS cells and the findings compared with cells that transiently expressed the wild-type human insulin receptor. Q-397 and Q-418 mutant insulin receptors had insulin-binding characteristics similar to the wild-type human insulin receptor, whereas no insulin-binding activity could be detected above the control level in cells transfected with Q-D. Flow cytometry with antibodies against the human insulin receptor indicated the presence of Q-397, Q-418, and wild-type human insulin receptors in the surface of COS cells and failed to demonstrate a Q-D receptor. Insulin-induced autophosphorylation was similar in Q-397, Q-418, and wild-type human insulin receptors as was their ability to phosphorylate an artificial substrate, poly Glu-Tyr (4:1). Our inability to detect Q-D receptors was not caused by a lack of Q-D mRNA. COS cells transfected with Q-D cDNA generated as much Q-D mRNA as the amount of wild-type human insulin receptor mRNA present in cells transfected with wild-type receptor cDNA. Finally, pulse-chase experiments with [35S]Met were able to detect 190,000-M(r) proreceptors and the alpha-subunits for Q-397, Q-418, and wild-type human insulin receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1993 Jul
PMID:Glycosylation of Asn397 or Asn418 is required for normal insulin receptor biosynthesis and processing. 851 78

Mutation of the insulin receptor gene can compromise the ability of the receptor to mediate insulin action. A homozygous point mutation that results in the substitution of histidine for arginine 252 in the insulin receptor alpha-subunit has now been identified by polymerase chain reaction and single stranded conformational polymorphism analysis in a 20-yr-old Japanese woman with type A syndrome and severe insulin resistance. The proband's consanguineous parents (diabetic mother and normal father) and her sister (impaired glucose tolerance), each of whom showed an exaggerated insulin response to an oral glucose load, were heterozygous for this mutation. Her brother showed a normal insulin response and lacked the mutation, as did 50 healthy Japanese control subjects. The chronic sc administration of insulin-like growth factor I (IGF-I) improved the patient's hyperglycemia and corrected certain metabolic abnormalities over a 9-month period, even though the binding of 125I-labeled IGF-I to her cultured fibroblasts was decreased by 40% relative to that to cells from healthy controls. Studies of the binding of 125I-labeled insulin to the proband's cultured fibroblasts, to COS-I cells transfected with complementary DNA encoding the mutant insulin receptor, and to partially purified mutant receptors revealed that the Arg252-->His mutation decreased both cell surface expression and the affinity for insulin for the receptor. These observations suggest that the homozygous Arg252-->His mutation is responsible for the type A insulin resistance of the proband, whereas in the heterozygous state, the mutation results in mild insulin resistance indistinguishable from that observed in noninsulin-dependent diabetes mellitus.
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PMID:Insulin resistance associated with substitution of histidine for arginine 252 in the alpha-subunit of the human insulin receptor: trial of insulin-like growth factor I injection therapy to enhance insulin sensitivity. 853 Jun 17

Cell-mediated autoimmune attack directed against islet proteins of approximately 38 kD in size has been associated with type 1 diabetes. A novel murine cDNA encoding an antigen of this size was cloned using a screening procedure based on the proliferative response of a human diabetic T cell clone (1C6) to a recombinant antigen epitope library. Membrane preparations from COS 7 cells transfected with the full-length 1,267-bp cDNA elicited a proliferative response from the reporter T cells comparable to that of the defined peptide epitope and native insulinoma antigen. In vitro translation and transfection experiments suggested that the protein is initially synthesized as a 44-kD protein and then processed to the native 38-kD form through the proteolytic removal of a 54-aa NH2-terminal mitochondrial targeting sequence. Differential centrifugation, Percoll density gradient centrifugation, and immunofluorescence studies confirmed localization of the antigen to mitochondria. Northern blot, Western blot, and 1C6 T cell proliferation assays showed that, although imogen 38 was more highly expressed in beta cell than alpha cell lines, it was also present in other tissues. It is concluded that imogen 38 may be a target for bystander autoimmune attack in diabetes rather than a primary autoantigen.
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PMID:Imogen 38: a novel 38-kD islet mitochondrial autoantigen recognized by T cells from a newly diagnosed type 1 diabetic patient. 856 80

We describe two Finnish kindreds with the Asn291 --> Ser mutation (A291S) of the lipoprotein lipase (LPL) gene. Sixteen subjects (9 male, 7 female) heterozygous for this mutation were studied and compared with 17 unaffected family members or spouses (family controls) and 19 unrelated healthy subjects (population controls). In the group of subjects heterozygous for the A291S mutation, postheparin plasma LPL activity was on average 23% lower than in the family controls and 29% lower than in the population controls. In agreement, in vitro expression studies with COS-7 cells showed that the mutant protein exhibits approximately 50% of the lipolytic activity of the wild-type protein. Median serum triglyceride concentration was 2.90 mmol/l in the group of heterozygotes, compared with 1.14 mmol/l in the family controls (P < 0.01) and 0.99 mmol/l in the population controls (P < 0.001). The heterozygotes also had a marked preponderance of small dense low density lipoproteins (LDL) as assessed by gradient gel electrophoresis. Nine of the heterozygous subjects were hypertriglyceridemic (serum triglyceride concentration > 2.0 mmol/l). Age or body mass index were not related to the presence of hypertriglyceridemia. By contrast, all hypertriglyceridemic subjects were either hyperinsulinemic (serum insulin concentration > 10 mU/l, n = 7) or had diabetes (n = 2). In a multivariate regression analysis, very low density lipoprotein (VLDL) triglyceride level was significantly and independently related to serum apolipoprotein B concentration, the presence of the A291S mutation, serum insulin concentration, and postheparin plasma LPL activity. The Asn291-->Ser mutation of the LPL gene results in reduced lipolytic activity. However, dyslipidemia appears to manifest only if VLDL production is also increased. Hyperinsulinemia was the major determinant of excessive VLDL synthesis and dyslipidemia among the subjects heterozygous for the A291S mutation in this study.
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PMID:Heterozygosity for Asn291-->Ser mutation in the lipoprotein lipase gene in two Finnish pedigrees: effect of hyperinsulinemia on the expression of hypertriglyceridemia. 873 73

Several proteins with NAD+:arginine ADP-ribosyltransferase (ART) activity are expressed in T cells and affect their function. Rat T cells that express the ART designated RT6 are determinants of the expression of autoimmune diabetes. In the mouse, a 35-kDa ecto-ART modulates the proliferation and functional activity of CTL. Here we report on mouse ARTs designated Rt6-1 and Rt6-2 in BALB/c and C57BL/6 mice. mRNAs for Rt6-1 and Rt6-2 were found in spleen, thymus, and intestinal tissue of both strains, but Rt6-1 mRNA in C57BL/6 mice was detected only at low levels. Rt6-1 and Rt6-2 cDNAs from both strains were cloned and sequenced. Predicted amino acid sequences of Rt6-2 were identical in both strains, but there was an in-frame stop codon in the sequence of Rt6-1 in C57BL/6 mice not present in BALB/c mice. Recombinant C57BL/6 Rt6-2 and BALB/c Rt6-1 proteins expressed in COS1 cells exhibited ART activity and were documented to be glycosylphosphatidylinositol-linked membrane proteins. COS-1 cells transfected with a C57BL/6 Rt6-1 cDNA construct expressed a truncated protein consistent in size with that predicted by the presence of the stop codon. This approximately 21-kDa protein appeared not to be glycosylphosphatidylinositol linked to the cell surface and lacked ART activity. C57BL/6 Rt6-1 therefore appears to be a naturally occurring ART knockout. The expression of Rt6-1 and Rt6-2 mRNAs in lymphoid tissues suggests that these ARTs may regulate immune system functions. Expression of Rt6-2 or another redundant ART may compensate for the lack of enzymatically active Rt6-1 in C57BL/6 mice.
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PMID:Expression in BALB/c and C57BL/6 mice of Rt6-1 and Rt6-2 ADP-ribosyltransferases that differ in enzymatic activity: C57BL/6 Rt6-1 is a natural transferase knockout. 930 Jun 95

ATP-sensitive potassium (K[ATP]) channels are an essential component of glucose-dependent insulin secretion in pancreatic islet beta-cells. These channels comprise the sulfonylurea receptor (SUR1) and Kir6.2, a member of the inward rectifier K+ channel family. Mutations in the SUR1 subunit are associated with familial hyperinsulinism (HI) (MIM:256450), an inherited disorder characterized by hyperinsulinism in the neonate. Since the Kir6.2 gene maps to human chromosome 11p15.1 (1,2), which also encompasses a locus for HI, we screened the Kir6.2 gene for the presence of mutations in 78 HI probands by single-strand conformation polymorphism (SSCP) and nucleotide sequence analyses. A nonsense mutation, Tyr-->Stop at codon 12 (designated Y12X) was observed in the homozygous state in a single proband. 86Rb+ efflux measurements and single-channel recordings of COS-1 cells co-expressing SUR1 and either wild-type or Y12X mutant Kir6.2 proteins confirmed that K(ATP) channel activity was abolished by this nonsense mutation. The identification of an HI patient homozygous for the Kir6.2/Y12X allele affords an opportunity to observe clinical features associated with mutations resulting in an absence of Kir6.2. These data provide evidence that mutations in the Kir6.2 subunit of the islet beta-cell K(ATP) channel are associated with the HI phenotype and also suggest that the majority of HI cases are not attributable to mutations in the coding region of the Kir6.2 gene.
Diabetes 1997 Nov
PMID:A nonsense mutation in the inward rectifier potassium channel gene, Kir6.2, is associated with familial hyperinsulinism. 935 20


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