Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cellular mechanism by which the specific binding of [125I]insulin to intact rat adipocytes is inhibited by isoproterenol has been studied. By exposing control and isoproterenol-treated cells to trypsin (0-150 micrograms/ml for 20 min at 4 degrees C) and measuring the intact insulin receptor pool following detergent solubilization, a differential sensitivity to proteolysis of the cell membrane receptor was observed. At low trypsin concentration (less than 30 micrograms/ml), approximately 40% of the specific insulin binding in isoproterenol-treated cells was insensitive to proteolysis as compared to control cells. At higher levels of trypsin (50-150 micrograms/ml) both groups displayed similar levels of trypsin-insensitive receptors which, at the highest trypsin concentration, accounted for 10% of the total receptors in intact cells. Detergent-solubilized receptors from isoproterenol-treated cells, on the other hand, exhibited the same sensitivity to trypsin proteolysis as solubilized receptors from control cells. The time course of the onset and reversal of the isoproterenol-induced binding alteration in intact adipocytes has been analyzed by mild trypsinization (20 micrograms/ml). Results indicated that insulin receptors resistant to trypsin under these conditions mediated the decreased surface binding and were re-expressed on the cell surface upon removal of isoproterenol. Experiments in which adipocytes were fractionated into plasma membrane and Golgi-enriched fractions indicated that the loss of surface insulin binding was not accompanied by a decrease in the proportion of receptors in the adipocyte plasma membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1988 Nov
PMID:Differential sensitivity of the insulin receptor to proteolysis after beta-adrenergic stimulation. 290 79

Incubation of isolated rat adipocytes with 1 microM arachidonic acid (20:4) coupled to equimolar amounts of bovine serum albumin (BSA) results in the cellular uptake of the fatty acid and a subsequent inhibition of insulin-stimulated antilipolysis and lipogenesis without altering glucose transport. These effects are apparently not mediated at the insulin receptor level since insulin binding is not altered in arachidonate-enriched fat cells. In addition, effects on antilipolytic and lipogenic are not specific for arachidonic acid. Oleic or palmitic acid can mimic these effects in both insulin-stimulated and PGE2-stimulated cells. Adipocyte enrichment with 20:4, however, specifically inhibits the insulin-stimulated turnover of phosphoinositides. The latter can be specifically prevented by preincubation with ibuprofen. These results suggest that the level of intracellular arachidonate may play a major role in modulating insulin-stimulated phosphoinositide turnover and thereby indirectly regulate certain aspects of insulin action which involve lipid metabolism.
Mol Cell Endocrinol 1986 May
PMID:Arachidonic acid inhibition of insulin action and phosphoinositide turnover in fat cells. 301 56

We isolated a human gene (designated c-ros-1) homologous to the v-ros sequence of UR2 sarcoma virus. Ten exons, 1,414 base pairs spanning 26 kilobases, contained a tyrosine kinase domain, a transmembrane domain, and a part of an extracellular domain carrying an N glycosylation site which was not acquired by UR2 sarcoma virus. The predicted structure of c-ros-1 is unique among the src family and clearly distinct from the human insulin receptor.
Mol Cell Biol 1986 Aug
PMID:Human c-ros-1 gene homologous to the v-ros sequence of UR2 sarcoma virus encodes for a transmembrane receptorlike molecule. 302 56

The evidence which suggests that a helper T (Th) cell recognizes a processed form of a soluble protein antigen in association with a class II MHC antigen on the surface of an antigen presenting cell (APC) has raised many questions and much controversy. A major question that remains unanswered is what is the cellular site(s) and mechanism(s) in which such an antigen is handled by an APC. The controversy relates to the issue of whether a protein antigen is required to be processed by an APC before it is presented to a Th cell. A currently favored hypothesis of antigen presentation, which stems mainly from analyses of T cell reactivity to peptides of protein antigens, is that such antigens are internalized by an APC, processed intracellularly, recycled to the cell surface and then presented to Th cells. As a first test of this hypothesis, we reasoned that although it is currently difficult to study the biochemistry of antigen processing, it is possible to study whether a protein antigen is internalized by an APC and recycled to its surface. In this report, colloidal gold conjugates of pork insulin (PI-Au), a tryptic peptide of pork insulin lacking the insulin receptor-binding portion of the molecule (TI-Au), myoglobin (MYO-Au), and apomyoglobin (APO-Au) were used to follow the pathway(s) and kinetics of antigen internalization and recycling in TA3 B hybridoma cells. Transmission electron micrographs of the routes followed by the PI-Au and TI-Au conjugates suggest that these antigens are internalized and recycled to the surface of an antigen presenting cell within 2-4 hr. In contrast, the patterns obtained for MYO-Au and APO-Au suggest that either the internalization of these antigens serves to channel them into a degradative pathway or that the kinetics of recycling of these antigens is slower. The two types of patterns observed may not be mutually exclusive and the purpose of internalization may vary, depending on the nature of the antigen. These data represent the first analysis of the kinetics and pathways of internalization and recycling of an antigen by an APC. It is impossible to formally prove that the pathway we have demonstrated is the one responsible for processing for antigen presentation. Nevertheless, these results support the notion that a protein antigen is handled intracellularly by an APC and recycled to the surface before it is presented to a Th cell.
J Mol Cell Immunol 1988
PMID:Ultrastructural study of internalization and recycling of antigen by antigen presenting cells. 307 24

The insulin receptor is an integral transmembrane glycoprotein comprised of two alpha-(approximately 135 kDa) and two beta-(approximately 95 kDa) subunits, which is synthesized as a single polypeptide chain precursor (alpha beta). The primary sequence of the human insulin receptor (hIR) protein, deduced from the nucleotide sequence of cloned human placental mRNAs, predicts two large domains (929 and 403 residues) on either side of a single membrane spanning domain (23 residues); each of these major domains has a distinct function (insulin binding and protein/tyrosine kinase activity, respectively). To experimentally test this deduced topology, and to explore the potential for independent domain function by the hIR extracellular domain, we have constructed an expression plasmid encoding an hIR deletion mutant which is truncated 8 residues from the beginning of the predicted transmembrane domain (i.e., 921 residues). This domain of the hIR is in fact processed into alpha- and truncated beta-subunits and secreted with high efficiency from transfected CHO cell lines which express this mutant hIR, and the protein accumulates as an (alpha beta)2 dimer in the medium. This molecule is recognized by a battery of 13 monoclonal antibodies to epitopes on the IR extracellular domain, four of which block insulin binding and two of which require the native conformation of the IR for recognition. Further, this domain binds insulin with an apparent dissociation constant comparable to that of the wild-type hIR. However, the secreted dimer displays a linear Scatchard plot, while that of the wild-type membrane-associated hIR is curvilinear.(ABSTRACT TRUNCATED AT 250 WORDS)
J Mol Recognit 1988 Feb
PMID:Truncation of the ectodomain of the human insulin receptor results in secretion of a soluble insulin binding protein from transfected CHO cells. 307 38

The insulin-binding and protein tyrosine kinase subunits of the Drosophila melanogaster insulin receptor homolog have been identified and characterized by using antipeptide antibodies elicited to the deduced amino acid sequence of the alpha and beta subunits of the human insulin receptor. In D. melanogaster embryos and cell lines, the insulin receptor contains insulin-binding alpha subunits of 110 or 120 kilodaltons (kDa), a 95-kDa beta subunit that is phosphorylated on tyrosine in response to insulin in intact cells and in vitro, and a 170-kDa protein that may be an incompletely processed receptor. All of the components are synthesized from a proreceptor, joined by disulfide bonds, and exposed on the cell surface. The beta subunit is recognized by an antipeptide antibody elicited to amino acids 1142 to 1162 of the human insulin proreceptor, and the alpha subunit is recognized by an antipeptide antibody elicited to amino acids 702 to 723 of the human proreceptor. Of the polypeptide ligands tested, only insulin reacts with the D. melanogaster receptor. Insulinlike growth factors type I and II, epidermal growth factor, and the silkworm insulinlike prothoracicotropic hormone are unable to stimulate autophosphorylation. Thus despite the evolutionary divergence of vertebrates and invertebrates, the essential features of the structure and intrinsic functions of the insulin receptor have been remarkably conserved.
Mol Cell Biol 1987 Aug
PMID:Structure and ligand specificity of the Drosophila melanogaster insulin receptor. 311 88

HL60 is a human promyeloid cell line capable of differentiating towards monocytes or granulocytes when treated with appropriate agents. Changes in insulin receptor number, affinity and mRNA levels were observed when HL60 cells were induced to differentiate with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or dimethylsulphoxide (DMSO). Total and high-affinity insulin receptor numbers decreased following treatment of HL60 cells with DMSO, whereas total insulin receptor number increased and high-affinity receptor number decreased in cells treated with TPA. Three distinct insulin receptor mRNA species of 9.1, 6.3 and 2.8 kb were identified in HL60 cells. The larger 9.1 and 6.3 kb species were increased in both TPA- and DMSO-treated HL60 cells, and the 2.8 kb mRNA was reduced in differentiated cells. Thus HL60 cells differentiated towards monocytes or granulocytes showed similar changes in the levels of individual insulin receptor mRNAs, but displayed contrasting alterations in low-affinity insulin binding. Three HL60 variant lines, which have different capacities to respond to inducers of monocyte and neutrophil differentiation, showed similar levels of total insulin receptors, but differed in their expression of high-affinity receptors. The data provide evidence for the existence of two distinct insulin receptors.
J Mol Endocrinol 1988 Nov
PMID:Changes in insulin receptor expression in HL60 cells induced to differentiate towards neutrophils or monocytes. 325 63

Previous studies have demonstrated differences in the size of insulin receptor subunits in brain and adipocytes that appear to involve variations in glycosylation of the proteins. In this report, we examined the degree of homology in the protein backbones of insulin receptors in both tissues by peptide mapping and compared the mRNAs encoding the receptors by Northern blot analysis. Photoaffinity-labeled insulin receptors from rat brain and adipocytes were deglycosylated and then subjected to partial proteolysis by five different enzymes with differing substrate specificities. The intact receptors and their proteolytic fragments were analyzed by electrophoresis and autoradiography. Each enzyme yielded a unique pattern of fragments ranging from 70 to 11 kDa. In all cases, there was a striking similarity in the peptide maps generated from insulin receptors in brain and adipocytes. Northern hybridization experiments were carried out using poly(A)+ RNA from rat brain, rat adipocytes, and human hepatocarcinoma (HEP G2) cells. In rat brain, two bands of 9.5 and 7.4 kb were detected and, in rat adipocytes, the same two bands were observed. The two mRNA bands observed in rat tissues represented only two of the five mRNA species seen in human HEP G2 cells. The results indicate that the protein domains and the mRNAs encoding of insulin receptors in brain and adipocytes are very similar, if not identical.
Mol Cell Endocrinol 1988 Apr
PMID:Peptide mapping on Northern blot analyses of insulin receptors in brain and adipocytes. 328 25

Insulin receptor beta-subunit autophosphorylation, the first event occurring after insulin binding, plays a crucial role in modulation of receptor-associated kinase activity towards exogenous substrates and possibly in the transmission of biological signals of insulin. Receptor autophosphorylation strongly depends on insulin receptor occupancy. Till now the effects of receptor phosphorylation on insulin binding itself have not been clarified. In the present report we demonstrate the absence of any feedback mechanism by which insulin receptor activation by phosphorylation affects binding affinity of insulin receptor itself.
Mol Cell Endocrinol 1986 May
PMID:Effect of insulin receptor autophosphorylation on insulin receptor binding. 351 15

When the insulin receptor is tagged with a 125I-photoreactive insulin analogue that can be covalently coupled to it by UV irradiation, the fate of this labeled receptor can be followed both morphologically and biochemically. In the present study we have applied this tool to trace the pathway followed by 125I-photoreactive insulin-receptor complex in hepatocytes in primary culture. As determined by quantitative electron microscopic autoradiography, the internalized labeled material first associates with clear vesicles, second is found in multivesicular bodies, third associates with dense bodies and fourth returns to the cell surface via clear vesicles. This recycling process is inhibited by lysosomotropic agents, i.e. NH4Cl or chloroquine. These data confirm, in another cell system, our previous observations carried out in freshly isolated rat hepatocytes and demonstrate the feasibility and complementarity of both freshly isolated hepatocytes and hepatocytes in primary culture to study internalization and recycling of the insulin receptor.
Mol Cell Endocrinol 1986 Oct
PMID:Internalization and recycling of 125I-photoreactive insulin-receptor complexes in hepatocytes in primary culture. 353 Aug 36


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>