Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An active 41 kDa cytoplasmic domain of the insulin receptor tyrosine kinase (CIRK-41) encompassing amino acid residues 946 and 1303 of the native protein with an additional three amino acids (HAI) at the N-terminus has been overexpressed using the baculovirus pAC 373 expression system. The recombinant protein termed CIRK-41 has been purified to homogeneity. CIRK-41 was capable of autophosphorylation and up to 1.9 moles of phosphate were incorporated per mole of enzyme when it was incubated in the presence of 10 mM manganese chloride and 0.5 mM ATP. Autophosphorylation resulted in stimulation of CIRK-41 activity towards its exogenous substrate, indicating that CIRK-41 may be used as a model molecule to study the role of phosphorylation and dephosphorylation in the control of the insulin receptor tyrosine kinase activity.
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PMID:Expression, purification and characterization of a 41 kDa insulin receptor tyrosine kinase domain. 233 26

To overcome the difficulties encountered in quantifying the insulin receptor number by Scatchard analysis, a radioimmunoassay (RIA) for the human insulin receptor (hIR) has been developed that uses an antibody raised against a synthetic peptide (Gly-Lys-Lys-Asn-Gly-Arg-Ile-Leu-Thr-Leu-Pro-Arg-Ser-Asn-Pro-Ser) corresponding to the carboxyl terminal of the hIR. A second peptide (Tyr-Gly-Arg-Ile-Leu-Thr-Leu-Pro-Arg-Ser-Asn-Pro-Ser) was used as a standard and allowed preparation of monoiodinated derivative of theoretical specific activity for use as the radioactive ligand. The assay is specific, highly reproducible, and sensitive, with a detection limit of 10 fmol of receptor. One mole of purified receptor, measured by Scatchard analysis or amino acid analysis, is read as one mole of receptor in the RIA with peptide being the standard. The assay is effective with receptor from multiple sources and could determine the decrease in number of insulin receptors seen in IM-9 lymphocytes after treatment with insulin (downregulation).
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PMID:Peptide-based radioimmunoassay for insulin receptor. Detection of insulin-stimulated downregulation in IM-9 lymphocytes. 266 3

Purified human placental insulin receptors were incorporated into small unilamellar phospholipid vesicles by the addition of n-octyl beta-glucopyranoside solubilized phospholipids, followed by removal of the detergent on a Sephadex G-50 gel filtration column and extensive dialysis. The vesicles have an average diameter of 142 +/- 24 nm by Sephacryl S-1000 gel filtration chromatography and 119 +/- 20 nm by transmission electron microscopy. These vesicles are impermeant to small molecules as indicated by their ability to retain [gamma-32P]ATP, which could be released by the addition of 0.05% Triton X-100. Detergent permeabilization or freeze-thawing of the insulin receptor containing vesicles in the presence of 125I-insulin indicated that approximately 75% of the insulin binding sites were oriented right side out (extravesicularly). Sucrose gradient centrifugation of insulin receptors incorporated at various protein to phospholipid mole ratios demonstrated that the insulin receptors were inserted into the phospholipid bilayer structure in a concentration-dependent manner. Addition of [gamma-32P]ATP to the insulin receptor containing vesicles was relatively ineffective in promoting the autophosphorylation of the beta subunit in the absence or presence of insulin. Permeabilization of the vesicles with low detergent concentrations, however, stimulated the beta-subunit autophosphorylation approximately 2-fold in the absence and 10-fold in the presence of insulin. Insulin-stimulated beta-subunit autophosphorylation was also observed under conditions such that 94% of those vesicles containing insulin receptors had a single receptor per vesicle, suggesting that the initial beta-subunit autophosphorylating activity is intramolecular. Phospho amino acid analysis of the vesicle-incorporated insulin receptors demonstrated that the basal and insulin-stimulated beta-subunit autophosphorylation occurs exclusively on tyrosine residues. It is concluded that when purified insulin receptors are incorporated into a phospholipid bilayer, they insert into the vesicles primarily in the same orientation as occurs in the plasma membrane of intact cells and retain insulin binding as well as insulin-stimulated beta-subunit autophosphorylating activities.
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PMID:Incorporation of the purified human placental insulin receptor into phospholipid vesicles. 408 39

Evaluation of insulin sensitivity in 12 patients with myotonic dystrophy gave results different from those found in other insulin-resistant conditions. Nine of our subjects were insensitive to exogenous insulin, but only three had elevated fasting insulin concentrations. Eight had an excessive insulin response to a glucose challenge. Monocyte insulin receptor affinity was decreased (myotonics, 1.21 +/- 0.74 X 10(9) liters per mole; controls, 2.62 +/- 1.28 X 10(9)), and this parameter correlated best with the insulin resistance. No circulating receptor antibody or insulin binding inhibitor was found. Our studies suggest that the insulin resistance seen in patients with myotonic dystrophy is related to decreased insulin receptor affinity.
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PMID:Insulin resistance in patients with myotonic dystrophy. 634 79

Inhibitor 2 is a heat-stable protein that complexes with the catalytic subunit of type-1 protein phosphatase. The reversible phosphorylation of Thr 72 of the inhibitor in this complex has been shown to regulate phosphatase activity. Here we show that inhibitor 2 can also be phosphorylated on tyrosine residues. Inhibitor 2 was 32P-labeled by the insulin receptor kinase in vitro, in the presence of polylysine. Phosphorylation of inhibitor 2 was accompanied by decreased electrophoretic mobility. Dephosphorylation of inhibitor 2 by tyrosine phosphatase 1B, restored normal electrophoretic mobility. Phosphotyrosine in inhibitor 2 was detected by immunoblotting with antiphosphotyrosine antibodies and phosphoamino acid analysis. In addition, following tryptic digestion, one predominant phosphopeptide was recovered at the anode. The ability of inhibitor 2 to inhibit type-1 phosphatase activity was diminished with increasing phosphorylation up to a stoichiometry of 1 mole phosphate incorporated/mole of inhibitor 2, where inhibitory activity was completely lost. These data demonstrate that inhibitor 2 can be phosphorylated on tyrosine residues by the insulin receptor kinase, resulting in a molecule with decreased ability to inhibit type-1 phosphatase activity.
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PMID:Tyrosine phosphorylation of phosphatase inhibitor 2. 776 77

The insulin receptor exists in two isoforms differing by the absence (HIR-A) or presence (HIR-B) of 12 amino acids in the COOH-terminus of the alpha-subunit as a consequence of alternative splicing of exon 11. In this study, we developed a radioimmunoassay for the two isoforms employing antibodies raised against two peptides, one (Pep-12) corresponding to residues encoded by exon 11, and the other (Pep-13) corresponding to a COOH-terminal domain of the alpha-subunit which is common to both HIR-A and HIR-B isoforms. These peptides were iodinated and used as both ligands and standards. The assay is specific, highly reproducible, and sensitive with a detection limit of 10 fmol of receptor. One mole of purified insulin receptor, measured by Scatchard analysis, is read as one mole of receptor in the radioimmunoassay with either Pep-12 or Pep-13 as standards. The radioimmunoassay is applicable to the measurement of total content and relative abundance of the two isoforms in extracts from various tissues. We applied the radioimmunoassay to measure the relative abundance of the two isoforms in fat and muscle from normal, obese non-diabetic and non-insulin-dependent diabetic (NIDDM) subjects. Results demonstrate that expression of the low-affinity HIR-B form is significantly increased in obese and NIDDM subjects compared with control subjects. In addition, the increased expression of the HIR-B isoform was significantly correlated with both body mass index (r = 0.52; p = 0.006) and fasting glucose levels (r = 0.59; p = 0.001).
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PMID:Peptide-based radioimmunoassay for the two isoforms of the human insulin receptor. 779 85

Insulin action and aspects of the insulin-signaling pathway have been studied in the heart although the direct regulation of the heart's insulin receptor has not been explored. This study describes the first purification and characterization of the mammalian (rabbit, rat and bovine) heart insulin receptor. The rabbit heart IR showed maximum insulin binding of 18 microg/mg (approximately 1 mole insulin/mole (alpha2beta2) receptor) and a curvilinear Scatchard plot with a high affinity KD for insulin binding of approximately 4 nM at optimal pH (7.8) and NaCl concentration (150 mM). The insulin receptor tyrosine kinase activity was stimulated by insulin, Mg2+ (half-maximum response at approximately 5.6-10.6 nM and approximately 8.5 mM, respectively) and by the physiological polyamines, spermine and spermidine. The stimulation by Mg2+ and the polyamines occurred with and without insulin. These characteristics of the heart insulin receptor provide a mechanism for regulating the activity of the receptor's tyrosine kinase activity by the intracellular free Mg2+ concentration and the polyamines in the absence and presence of insulin.
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PMID:Regulation of heart insulin receptor tyrosine kinase activity by magnesium and spermine. 1613 9

Choriocarcinoma is a highly malignant tumor that can arise from trophoblasts of any type of gestational event but most often from complete hydatidiform mole. IGF-II plays a fundamental role in placental development and may play a role in gestational trophoblastic diseases. Several studies have shown that IGF-II is expressed at high levels in hydatidiform moles and choriocarcinoma tissues; however, conflicting data exist on how IGF-II regulates the behaviour of choriocarcinoma cells. The purpose of this study was to determine the contribution of the receptors for IGF-I and insulin to the actions of IGF-II on the regulation of choriocarcinoma cells metastasis. An Immuno Radio Metric Assay was used to analyse the circulating and tissue levels of IGF-I and IGF-II in 24 cases of hydatidiform mole, two cases of choriocarcinoma and eight cases of spontaneous abortion at the same gestational age. The JEG-3 choriocarcinoma cell line was used to investigate the role of IGF-II in the regulation of cell invasion. We found that mole and choriocarcinoma tissue express high levels of IGF-II compared to first trimester placenta. Both IGF-I and IGF-II regulate choriocarcinoma cell invasion in a dose dependent manner but through a different mechanism. IGF-II effects involve the activation of the InsR while IGF-I uses the IGF-IR. The positive effects of IGF-II on invasion are the result of enhanced cell adhesion and chemotaxis (specifically towards collagen IV). The actions of IGF-II but not those of IGF-I were sensitive to inhibition by the insulin receptor inhibitor HNMPA(AM)3. Our results demonstrate that the insulin receptor regulates choriocarcinoma cell invasion.
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PMID:IGF-II regulates metastatic properties of choriocarcinoma cells through the activation of the insulin receptor. 1755 77