1
|
Dalle S, Imamura T, Rose DW, Worrall DS, Ugi S, Hupfeld CJ, Olefsky JM. Insulin induces heterologous desensitization of G-protein-coupled receptor and insulin-like growth factor I signaling by downregulating beta-arrestin-1. Mol Cell Biol 2002; 22:6272-85. [PMID: 12167719 PMCID: PMC134007 DOI: 10.1128/mcb.22.17.6272-6285.2002] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
beta-Arrestin-1 mediates agonist-dependent desensitization and internalization of G protein-coupled receptors (GPCRs) and is also essential for GPCR mitogenic signaling. In addition, insulin-like growth factor I receptor (IGF-IR) endocytosis is facilitated by beta-arrestin-1, and internalization is necessary for IGF-I-stimulated mitogen-activated protein (MAP) kinase activation. Here, we report that treatment of cells for 12 h with insulin (100 ng/ml) induces an approximately 50% decrease in cellular beta-arrestin-1 content due to ubiquitination of beta-arrestin-1 and proteosome-mediated degradation. This insulin-induced decrease in beta-arrestin-1 content was blocked by inhibition of phosphatidylinositol-3 kinase (PI-3 kinase) and MEK with wortmannin and PD98059, respectively. We also found a marked decrease in the association of beta-arrestin-1 with the IGF-IR and a 55% inhibition of IGF-I-stimulated MAP kinase phosphorylation. In insulin-treated, beta-arrestin-1-downregulated cells, there was complete inhibition of lysophosphatidic acid (LPA) or isoproterenol (ISO)-stimulated MAP kinase phosphorylation. This was associated with a decrease in beta-arrestin-1 association with the beta2-AR as well as a decrease in beta-arrestin-1-Src and Src-beta2-AR association. Ectopic expression of wild-type beta-arrestin-1 in insulin-treated cells in which endogenous beta-arrestin-1 had been downregulated rescued IGF-I- and LPA-stimulated MAP kinase phosphorylation. In conclusion, we found the following. (i) Chronic insulin treatment leads to enhanced beta-arrestin-1 degradation. (ii) This downregulation of endogenous beta-arrestin-1 is associated with decreased IGF-I-, LPA-, and ISO-mediated MAP kinase signaling, which can be rescued by ectopic expression of wild-type beta-arrestin-1. (iii) Finally, these results describe a novel mechanism for heterologous desensitization, whereby insulin treatment can impair GPCR signaling, and highlight the importance of beta-arrestin-1 as a target molecule for this desensitization mechanism.
Collapse
Affiliation(s)
- Stéphane Dalle
- Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, California 92093-0673, USA
| | | | | | | | | | | | | |
Collapse
|
2
|
Sasaoka T, Langlois WJ, Rose DW, Olefsky JM. Mechanisms of enhanced transmembrane signaling by an insulin receptor lacking a cytoplasmic beta-subunit domain. J Biol Chem 1995; 270:10885-92. [PMID: 7738028 DOI: 10.1074/jbc.270.18.10885] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We have recently characterized a mutant insulin receptor (HIR delta 978) in which the insulin receptor beta-subunit was truncated at amino acid residue 978. Compared with parental Rat1 cells, the cells expressing the truncated receptor exhibited enhanced sensitivity to insulin's biologic actions. All of these effects are now extended to transcriptional events, since we now show enhanced sensitivity to insulin stimulation of c-fos mRNA expression. These effects were insulin-specific, since insulin-like growth factor-1 stimulation of glucose incorporation into glycogen, alpha-aminoisobutyric acid uptake, and thymidine incorporation into DNA were normal. In addition, the truncated receptor exhibited enhanced sensitivity only in vivo, but not in vitro, since the kinase activity of wheat germ agglutinin-purified receptor preparations was comparable between HIR delta 978 and parental Rat1 insulin receptors. Parental rat endogenous insulin-like growth factor-1 receptors and transfected human insulin receptors form hybrid receptors as well as homologous tetrameric receptors. The normal heterotetrameric receptors possess kinase activity in vivo leading to tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) and its association with the p85 regulatory subunit of phosphatidyl inositol 3-kinase. Interestingly, preincubation with human-specific anti-insulin receptor antibody abolished the increased insulin sensitivity in glucose incorporation into glycogen in HIR delta 978 cells. Furthermore, microinjection of anti-IRS-1 antibody into HIR delta 978 cells inhibited insulin stimulation of DNA synthesis. In summary: 1) truncated receptors on the cell surface confer enhanced insulin sensitivity in vivo; 2) the normal heterotetrameric receptors are functionally active and couple to IRS-1 efficiently; and 3) IRS-1 is an important molecule transmitting insulin's biological signals in HIR delta 978 cells.
Collapse
Affiliation(s)
- T Sasaoka
- Department of Medicine, University of California, San Diego, La Jolla 92093, USA
| | | | | | | |
Collapse
|
3
|
Carpentier JL, McClain D. Insulin receptor kinase activation releases a constraint maintaining the receptor on microvilli. J Biol Chem 1995; 270:5001-6. [PMID: 7890606 DOI: 10.1074/jbc.270.10.5001] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
To examine whether the surface redistribution of the insulin receptor from microvilli, where it sits in its unoccupied form, to the nonvillous domain, where it is internalized through clathrin-coated pits, is an active movement or a passive redistribution linked to the release of a restraint maintaining it on microvilli, we have generated a mutated insulin receptor with a truncation of exons 17-22 and tracked it biochemically and morphologically. Biochemical analysis indicates that this mutated receptor is constitutively internalized and recycled even in the absence of ligand. Quantitative electron microscope autoradiography analysis reveals that it does not preferentially associate with microvilli in its unoccupied form but is normally segregated in clathrin-coated pits through the preserved signal sequence(s) of exon 16. We conclude that (a) insulin receptor internalization initiated through receptor kinase activation and autophosphorylation, which free the receptor from constraints maintaining it on microvilli; (b) the signal sequences contained in exon 16 are entirely sufficient to promote clathrin-coated pit-mediated internalization of insulin receptors; (c) these sequences are not uncovered by kinase activation; and (d) the "code" maintaining the unoccupied receptors on microvilli is contained within exons 17-21 of the receptor.
Collapse
Affiliation(s)
- J L Carpentier
- Department of Morphology, University of Geneva, School of Medicine, Switzerland
| | | |
Collapse
|
4
|
Yip CC, Hsu H, Olefsky JM, Seely L. Preparation of N epsilon B28-monoazidobenzoyl insulin-like growth factor I and photoaffinity labeling of insulin-like growth factor I receptor. Peptides 1993; 14:325-30. [PMID: 8483809 DOI: 10.1016/0196-9781(93)90048-l] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Recombinant human insulin-like growth factor I (hIGF-I) was reacted with azidobenzoyl hydroxysuccinimide to produce a mixture of photoactive hIGF-I derivatives. The mixture was purified by reversed-phase HPLC to yield three mono-substituted azidobenzoyl hIGF-Is. One of the derivatives was identified by amino acid sequencing as N epsilon B28-monoazidobenzoyl hIGF-I. This derivative was indistinguishable from native hIGF-I when bioassayed in Rat-1 fibroblasts. A 120-kDa band, the alpha subunit of the IGF-I receptor, was specifically labeled in Rat-1 plasma membranes by this photoprobe. The labeling of this band was reduced by hIGF-I at 1 nM and completely abolished by hIGF-I, but not insulin, at 100 nM, indicating the specificity of the photolabeling of the IGF-I receptor by this fully active IGF-I photoprobe.
Collapse
Affiliation(s)
- C C Yip
- Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada
| | | | | | | |
Collapse
|
5
|
Lee AW. Signal transduction by the colony-stimulating factor-1 receptor; comparison to other receptor tyrosine kinases. CURRENT TOPICS IN CELLULAR REGULATION 1992; 32:73-181. [PMID: 1318184 DOI: 10.1016/b978-0-12-152832-4.50005-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- A W Lee
- Clinical Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
| |
Collapse
|
6
|
Rajagopalan M, Neidigh J, McClain D. Amino acid sequences Gly-Pro-Leu-Tyr and Asn-Pro-Glu-Tyr in the submembranous domain of the insulin receptor are required for normal endocytosis. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54464-1] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
7
|
Kusari J, Takata Y, Hatada E, Freidenberg G, Kolterman O, Olefsky JM. Insulin resistance and diabetes due to different mutations in the tyrosine kinase domain of both insulin receptor gene alleles. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(19)67781-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
8
|
Moises RS, Heidenreich KA. Pertussis toxin catalyzed ADP-ribosylation of a 41 kDa G-protein impairs insulin-stimulated glucose metabolism in BC3H-1 myocytes. J Cell Physiol 1990; 144:538-45. [PMID: 2118147 DOI: 10.1002/jcp.1041440323] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In this study, we examined the effects of pertussis toxin (PT) on the ADP-ribosylation of guanine nucleotide binding proteins (G-proteins) and various insulin-stimulated processes in cultured BC3H-1 myocytes. Treatment of intact myocytes with 0.1 microgram/ml PT for 24 hours resulted in the complete ribosylation of a 41 kDa protein. The 41 kDa PT substrate was immunoprecipitated with antibodies directed against a synthetic peptide corresponding to a unique sequence in the alpha subunit of Gi-proteins. PT treatment of intact cells had no effect on insulin receptor binding or internalization. However, PT inhibited insulin-stimulated glucose transport at all insulin-concentrations tested (1-100 ng/ml). Maximally stimulated glucose transport was reduced by 50% +/- 15%. Insulin-stimulated glucose oxidation was also decreased by 31% +/- 8%. The toxin had no significant effect on the basal rates of glucose transport and glucose oxidation. The time course of PT-induced inhibition on glucose transport correlated with the time course of the "in vivo" ADP-ribosylation of the 41 kDa protein. The results suggest that a 41 kDa PT-sensitive G-protein, identical or very similar to Gi, is involved in the regulation of glucose metabolism by insulin in BC3H-1 cells.
Collapse
Affiliation(s)
- R S Moises
- Department of Medicine, University of California, San Diego, La Jolla 92093
| | | |
Collapse
|
9
|
Thies RS, Webster NJ, McClain DA. A domain of the insulin receptor required for endocytosis in rat fibroblasts. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)38789-7] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
|
10
|
Levy JR, Belsky M. Down-regulated insulin receptors in HepG2 cells have an altered intracellular itinerary. Am J Med Sci 1990; 299:302-8. [PMID: 2159709 DOI: 10.1097/00000441-199005000-00003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The delivery of insulin and the insulin receptor into an intracellular compartment may be important for eliciting some of the biologic responses of the cell to the hormone. Internalization of insulin-receptor complexes in cells from hyperinsulinemic type II diabetic patients is diminished, suggesting a possible role for this cellular process in insulin resistance. To examine whether hyperinsulinemia contributes to defective insulin-receptor processing in vitro, cultured hepatoma cells (HepG2) were incubated with high concentrations of (500 ng/ml) insulin from 1-3 days. Insulin induced a decrease in the number of total and surface insulin receptors within 24 hours; however, the hormone did not mediate a change in the number of intracellular receptors. The cellular itinerary of control and down-regulated receptors were then compared. Insulin mediated internalization of down-regulated receptors was impaired compared to control receptors; however, the down-regulated receptors that were internalized recycled back to the plasma membrane more efficiently. By covalently labeling the insulin receptor with the photoactive insulin derivative, 125I-NAPA-DP-insulin, it was demonstrated that the rates of receptor degradation of down-regulated and control receptors were similar. These results suggest that incubating HepG2 cells with high concentrations of insulin alters the cellular itinerary of the insulin receptor.
Collapse
Affiliation(s)
- J R Levy
- Department of Medicine, Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia
| | | |
Collapse
|
11
|
Insulin receptors with defective tyrosine kinase inhibit normal receptor function at the level of substrate phosphorylation. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)37800-1] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
|
12
|
Heidenreich KA, de Vellis G, Gilmore PR. Functional properties of the subtype of insulin receptor found on neurons. J Neurochem 1988; 51:878-87. [PMID: 3045261 DOI: 10.1111/j.1471-4159.1988.tb01824.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In this report, we have examined the structure, regulation, and function of insulin receptors in cultured neurons from fetal chicken brain. The apparent molecular weight of the alpha-subunit of neuronal insulin receptors, analyzed by photoaffinity labeling and sodium dodecyl sulfate gel electrophoresis under reducing conditions, was 115,000. The number of insulin receptors in the cultures increased from day 2 to day 4 during a period of extensive process formation. After 5 days in culture, there were approximately 40,000 high-affinity insulin receptors per neuron. When neurons were photoaffinity labeled at 16 degrees C and then warmed to 37 degrees C for 30 min, approximately 40% of the cell-surface receptors were recovered in the intracellular, trypsin-insensitive pool. Chronic exposure of neurons to insulin (100 ng/ml) resulted in a time-dependent loss of neuronal insulin receptors with a maximal decrease of 50% after 24 h. Insulin had no effect on glucose transport, glucose oxidation, or glycogen synthase activity in neurons. On the other hand, insulin supported the growth and differentiation of a fraction of neurons isolated from chick forebrain. We conclude that (1) cultured neurons from fetal chicken brain express the same subtype of insulin receptor previously identified in adult rat and human brain, (2) the neuronal subtype of insulin receptor undergoes internalization and down-regulation in response to insulin, and (3) neuronal insulin receptors do not acutely regulate glucose metabolism but mediate growth in neurons.
Collapse
Affiliation(s)
- K A Heidenreich
- Department of Medicine, University of California, San Diego, La Jolla 92093
| | | | | |
Collapse
|
13
|
|
14
|
Properties of a human insulin receptor with a COOH-terminal truncation. I. Insulin binding, autophosphorylation, and endocytosis. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68393-0] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
15
|
Berhanu P. Internalized insulin-receptor complexes are unidirectionally translocated to chloroquine-sensitive degradative sites. Dependence on metabolic energy. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)60660-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
|
16
|
A mutant insulin receptor with defective tyrosine kinase displays no biologic activity and does not undergo endocytosis. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)47847-7] [Citation(s) in RCA: 265] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
|
17
|
Radiation inactivation target size of rat adipocyte glucose transporters in the plasma membrane and intracellular pools. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)47531-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
|
18
|
Hachiya H, Takayama S, White M, King G. Regulation of insulin receptor internalization in vascular endothelial cells by insulin and phorbol ester. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)45586-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
19
|
Podlecki D, Smith R, Kao M, Tsai P, Huecksteadt T, Brandenburg D, Lasher R, Jarett L, Olefsky J. Nuclear translocation of the insulin receptor. A possible mediator of insulin's long term effects. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)61511-x] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
20
|
The covalent tagging of the cell surface insulin receptor in intact cells with the generation of an insulin-free, functional receptor. A new approach to the study of receptor dynamics. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)61665-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
21
|
Jochen A, Berhanu P. Effects of metalloendoprotease inhibitors on insulin binding, internalization and processing in adipocytes. Biochem Biophys Res Commun 1987; 142:205-12. [PMID: 3545203 DOI: 10.1016/0006-291x(87)90472-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The effects of metalloendoprotease inhibitors on insulin binding, internalization, and processing were studied in isolated rat adipocytes. The metalloendoprotease inhibitor phosphoramidon caused a marked (threefold) increase in intracellular insulin accumulation without affecting surface binding. The dipeptide metalloendoprotease substrate analogues benzyloxycarbonyl-Gly-Phe-NH2 and benzyloxycarbonyl-Gly-Leu-NH2 caused similar large increases in intracellular insulin but also caused a doubling of cell surface bound insulin. The effect on surface binding was due to increased insulin receptor affinity as demonstrated by Scatchard analysis and the benzyloxycarbonyl-Gly-Phe NH2 induced inhibition of the dissociation of prebound insulin from the cell surface. These results suggest a role for endogenous metalloendoprotease-like enzymes in insulin processing by rat adipocytes.
Collapse
|
22
|
Huecksteadt T, Olefsky JM, Brandenberg D, Heidenreich KA. Recycling of photoaffinity-labeled insulin receptors in rat adipocytes. Dissociation of insulin-receptor complexes is not required for receptor recycling. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(19)84430-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
23
|
Ezaki O, Kasuga M, Akanuma Y, Takata K, Hirano H, Fujita-Yamaguchi Y, Kasahara M. Recycling of the glucose transporter, the insulin receptor, and insulin in rat adipocytes. Effect of acidtropic agents. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)35781-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
24
|
Wilson C, Peterson SW. Insulin receptor processing as a function of erythrocyte age. A kinetic model for down-regulation. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)35906-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
|
25
|
The effects of cycloheximide and chloroquine on insulin receptor metabolism. Differential effects on receptor recycling and inactivation and insulin degradation. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)38700-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
26
|
Brandenburg D, Diaconescu C, Klotz G, Mucke P, Neffe J, Saunders D, Schüttler A. Biological action and fate of photoaffinity-labelled insulin-receptor complexes. Biochimie 1985; 67:1111-7. [PMID: 3907715 DOI: 10.1016/s0300-9084(85)80108-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Covalent linking of two photoactivatable insulin derivatives, B2-(2-nitro,4-azidophenylacetyl)-des-PheB1-insulin and B29-(2-nitro,4-azidophenylacetyl)-insulin to viable rat adipocytes gives a system, which contains a fixed stoichiometry between hormone and receptor. The biological signal of prolonged lipogenesis has been used to study several aspects of insulin binding and action: the role of the site of the crosslink between insulin and receptor, recognition of bound photoinsulin by anti-insulin antibodies, the half-life of the biologically active complex, the pH-dependence of the biological signal, and the possible role of internalization. Furthermore, the effect of trypsin on the insulin receptor, as well as the insulin-receptor complex, has been investigated and a refined model of the receptor is presented.
Collapse
|
27
|
Capeau J, Lascols O, Flaig-Staedel C, Blivet MJ, Beck JP, Picard J. Degradation of insulin receptors by hepatoma cells: insulin-induced down-regulation results from an increase in the rate of basal receptor degradation. Biochimie 1985; 67:1133-41. [PMID: 3907717 DOI: 10.1016/s0300-9084(85)80111-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The degradation of insulin receptors was studied in cultured Zajdela hepatoma cells (ZHC). Receptor distribution within the cell was evaluated by estimating: i) surface receptor level on entire cells, ii) total cell receptors solubilized by Triton from cell membranes and iii) intracellular receptors solubilized from cells whose surface receptors had been inactivated with trypsin. In the absence of insulin, 80-90% of the insulin binding sites were located on the cell surface. When insulin was added, a rapid decrease of surface receptors was observed. After 2 h, their level was reduced nearly by half; this reduction was accounted for by an actual receptor loss from the cell without an increase in the intracellular pool. These results indicate that insulin enhanced the rate of receptor degradation within the cell. Basal receptor inactivation was studied by using tunicamycin which inhibits new receptor synthesis. The surface receptor number was decreased with a half-life of 7 h, while the level of internal sites remained unchanged. Both basal and insulin-activated receptor degradation were markedly slowed down by chloroquine or dansylcadaverine, indicating the importance of endocytic pathways in this process. Similarly, when de novo protein glycosylation was inhibited for 24 h by tunicamycin, both basal and insulin-activated receptor inactivation were precluded.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
|
28
|
|
29
|
Marshall S. Kinetics of insulin receptor internalization and recycling in adipocytes. Shunting of receptors to a degradative pathway by inhibitors of recycling. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(18)89242-0] [Citation(s) in RCA: 68] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
30
|
|
31
|
Horuk R, Olefsky JM. Post binding events in insulin action. DIABETES/METABOLISM REVIEWS 1985; 1:59-97. [PMID: 3915252 DOI: 10.1002/dmr.5610010105] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|