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Rachubik P, Rogacka D, Audzeyenka I, Typiak M, Wysocka M, Szrejder M, Lesner A, Piwkowska A. Role of lysosomes in insulin signaling and glucose uptake in cultured rat podocytes. Biochem Biophys Res Commun 2023; 679:145-159. [PMID: 37696068 DOI: 10.1016/j.bbrc.2023.09.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 08/30/2023] [Accepted: 09/05/2023] [Indexed: 09/13/2023]
Abstract
Podocytes are sensitive to insulin, which governs the functional and structural integrity of podocytes that are essential for proper function of the glomerular filtration barrier. Lysosomes are acidic organelles that are implicated in regulation of the insulin signaling pathway. Cathepsin D (CTPD) and lysosome-associated membrane protein 1 (LAMP1) are major lysosomal proteins that reflect the functional state of lysosomes. However, the effect of insulin on lysosome activity and role of lysosomes in the regulation of insulin-dependent glucose uptake in podocytes are unknown. Our studies showed that the short-term incubation of podocytes with insulin decreased LAMP1 and CTPD mRNA levels. Insulin and bafilomycin A1 reduced both the amounts of LAMP1 and CTPD proteins and activity of CTPD, which were associated with a decrease in the fluorescence intensity of lysosomes that were labeled with LysoTracker. Bafilomycin A1 inhibited insulin-dependent endocytosis of the insulin receptor and increased the amounts of the insulin receptor and glucose transporter 4 on the cell surface of podocytes. Bafilomycin A1 also inhibited insulin-dependent glucose uptake despite an increase in the amount of glucose transporter 4 in the plasma membrane of podocytes. These results suggest that lysosomes are signaling hubs that may be involved in the coupling of insulin signaling with the regulation of glucose uptake in podocytes. The dysregulation of this mechanism can lead to the dysfunction of podocytes and development of insulin resistance.
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Affiliation(s)
- Patrycja Rachubik
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Wita Stwosza 63 St, Gdansk, 80-308, Poland.
| | - Dorota Rogacka
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Wita Stwosza 63 St, Gdansk, 80-308, Poland; Faculty of Chemistry, University of Gdansk, Wita Stwosza 63 St, Gdansk, 80-308, Poland.
| | - Irena Audzeyenka
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Wita Stwosza 63 St, Gdansk, 80-308, Poland; Faculty of Chemistry, University of Gdansk, Wita Stwosza 63 St, Gdansk, 80-308, Poland.
| | - Marlena Typiak
- Department of General and Medical Biochemistry, Faculty of Biology, University of Gdansk, Wita Stwosza 59 St, Gdansk, 80-308, Poland.
| | - Magdalena Wysocka
- Faculty of Chemistry, University of Gdansk, Wita Stwosza 63 St, Gdansk, 80-308, Poland.
| | - Maria Szrejder
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Wita Stwosza 63 St, Gdansk, 80-308, Poland.
| | - Adam Lesner
- Faculty of Chemistry, University of Gdansk, Wita Stwosza 63 St, Gdansk, 80-308, Poland.
| | - Agnieszka Piwkowska
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Wita Stwosza 63 St, Gdansk, 80-308, Poland; Faculty of Chemistry, University of Gdansk, Wita Stwosza 63 St, Gdansk, 80-308, Poland.
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Koh HCE, Cao C, Mittendorfer B. Insulin Clearance in Obesity and Type 2 Diabetes. Int J Mol Sci 2022; 23:596. [PMID: 35054781 PMCID: PMC8776220 DOI: 10.3390/ijms23020596] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 01/02/2022] [Accepted: 01/03/2022] [Indexed: 02/06/2023] Open
Abstract
Plasma insulin clearance is an important determinant of plasma insulin concentration. In this review, we provide an overview of the factors that regulate insulin removal from plasma and discuss the interrelationships among plasma insulin clearance, excess adiposity, insulin sensitivity, and type 2 diabetes (T2D). We conclude with the perspective that the commonly observed lower insulin clearance rate in people with obesity, compared with lean people, is not a compensatory response to insulin resistance but occurs because insulin sensitivity and insulin clearance are mechanistically, directly linked. Furthermore, insulin clearance decreases postprandially because of the marked increase in insulin delivery to tissues that clear insulin. The commonly observed high postprandial insulin clearance in people with obesity and T2D likely results from the relatively low insulin secretion rate, not an impaired adaptation of tissues that clear insulin.
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Affiliation(s)
| | | | - Bettina Mittendorfer
- Center for Human Nutrition, Washington University School of Medicine, 660 S Euclid Ave, Campus Box 8031-14-0002, St. Louis, MO 63110, USA; (H.-C.E.K.); (C.C.)
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Chen Y, Huang L, Qi X, Chen C. Insulin Receptor Trafficking: Consequences for Insulin Sensitivity and Diabetes. Int J Mol Sci 2019; 20:ijms20205007. [PMID: 31658625 PMCID: PMC6834171 DOI: 10.3390/ijms20205007] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 10/04/2019] [Accepted: 10/08/2019] [Indexed: 12/12/2022] Open
Abstract
Insulin receptor (INSR) has been extensively studied in the area of cell proliferation and energy metabolism. Impaired INSR activities lead to insulin resistance, the key factor in the pathology of metabolic disorders including type 2 diabetes mellitus (T2DM). The mainstream opinion is that insulin resistance begins at a post-receptor level. The role of INSR activities and trafficking in insulin resistance pathogenesis has been largely ignored. Ligand-activated INSR is internalized and trafficked to early endosome (EE), where INSR is dephosphorylated and sorted. INSR can be subsequently conducted to lysosome for degradation or recycled back to the plasma membrane. The metabolic fate of INSR in cellular events implies the profound influence of INSR on insulin signaling pathways. Disruption of INSR-coupled activities has been identified in a wide range of insulin resistance-related diseases such as T2DM. Accumulating evidence suggests that alterations in INSR trafficking may lead to severe insulin resistance. However, there is very little understanding of how altered INSR activities undermine complex signaling pathways to the development of insulin resistance and T2DM. Here, we focus this review on summarizing previous findings on the molecular pathways of INSR trafficking in normal and diseased states. Through this review, we provide insights into the mechanistic role of INSR intracellular processes and activities in the development of insulin resistance and diabetes.
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Affiliation(s)
- Yang Chen
- School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia.
| | - Lili Huang
- School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia.
| | - Xinzhou Qi
- School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia.
| | - Chen Chen
- School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia.
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4
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Schulze RJ, Schott MB, Casey CA, Tuma PL, McNiven MA. The cell biology of the hepatocyte: A membrane trafficking machine. J Cell Biol 2019; 218:2096-2112. [PMID: 31201265 PMCID: PMC6605791 DOI: 10.1083/jcb.201903090] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 05/24/2019] [Accepted: 05/28/2019] [Indexed: 12/24/2022] Open
Abstract
The liver performs numerous vital functions, including the detoxification of blood before access to the brain while simultaneously secreting and internalizing scores of proteins and lipids to maintain appropriate blood chemistry. Furthermore, the liver also synthesizes and secretes bile to enable the digestion of food. These diverse attributes are all performed by hepatocytes, the parenchymal cells of the liver. As predicted, these cells possess a remarkably well-developed and complex membrane trafficking machinery that is dedicated to moving specific cargos to their correct cellular locations. Importantly, while most epithelial cells secrete nascent proteins directionally toward a single lumen, the hepatocyte secretes both proteins and bile concomitantly at its basolateral and apical domains, respectively. In this Beyond the Cell review, we will detail these central features of the hepatocyte and highlight how membrane transport processes play a key role in healthy liver function and how they are affected by disease.
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Affiliation(s)
- Ryan J Schulze
- Division of Gastroenterology and Hepatology, Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN
| | - Micah B Schott
- Division of Gastroenterology and Hepatology, Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN
| | - Carol A Casey
- Research Service, Department of Veterans Affairs, Nebraska-Western Iowa Health Care System, Omaha, NE
- Departments of Internal Medicine and Biochemistry & Molecular Biology, University of Nebraska Medical Center, Omaha, NE
| | | | - Mark A McNiven
- Division of Gastroenterology and Hepatology, Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN
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5
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Bhattacharya S, Maji U, Khan GA, Das R, Sinha AK, Ghosh C, Maiti S. Antidiabetic role of a novel protein from garlic via NO in expression of Glut-4/insulin in liver of alloxan induced diabetic mice. Biomed Pharmacother 2019; 111:1302-1314. [DOI: 10.1016/j.biopha.2019.01.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 01/02/2019] [Accepted: 01/09/2019] [Indexed: 12/25/2022] Open
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Willoughby LF, Manent J, Allan K, Lee H, Portela M, Wiede F, Warr C, Meng TC, Tiganis T, Richardson HE. Differential regulation of protein tyrosine kinase signalling by Dock and the PTP61F variants. FEBS J 2017; 284:2231-2250. [PMID: 28544778 DOI: 10.1111/febs.14118] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 04/12/2017] [Accepted: 05/19/2017] [Indexed: 01/01/2023]
Abstract
Tyrosine phosphorylation-dependent signalling is coordinated by the opposing actions of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). There is a growing list of adaptor proteins that interact with PTPs and facilitate the dephosphorylation of substrates. The extent to which any given adaptor confers selectivity for any given substrate in vivo remains unclear. Here we have taken advantage of Drosophila melanogaster as a model organism to explore the influence of the SH3/SH2 adaptor protein Dock on the abilities of the membrane (PTP61Fm)- and nuclear (PTP61Fn)-targeted variants of PTP61F (the Drosophila othologue of the mammalian enzymes PTP1B and TCPTP respectively) to repress PTK signalling pathways in vivo. PTP61Fn effectively repressed the eye overgrowth associated with activation of the epidermal growth factor receptor (EGFR), PTK, or the expression of the platelet-derived growth factor/vascular endothelial growth factor receptor (PVR) or insulin receptor (InR) PTKs. PTP61Fn repressed EGFR and PVR-induced mitogen-activated protein kinase signalling and attenuated PVR-induced STAT92E signalling. By contrast, PTP61Fm effectively repressed EGFR- and PVR-, but not InR-induced tissue overgrowth. Importantly, coexpression of Dock with PTP61F allowed for the efficient repression of the InR-induced eye overgrowth, but did not enhance the PTP61Fm-mediated inhibition of EGFR and PVR-induced signalling. Instead, Dock expression increased, and PTP61Fm coexpression further exacerbated the PVR-induced eye overgrowth. These results demonstrate that Dock selectively enhances the PTP61Fm-mediated attenuation of InR signalling and underscores the specificity of PTPs and the importance of adaptor proteins in regulating PTP function in vivo.
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Affiliation(s)
| | - Jan Manent
- Department of Biochemistry & Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Kirsten Allan
- Department of Biochemistry & Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Han Lee
- Institute of Biochemical Sciences, National Taiwan University, and Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Marta Portela
- Department of Biochemistry & Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Florian Wiede
- Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.,Department of Biochemistry & Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Coral Warr
- School of Biomedical Sciences, Monash University, Clayton, Victoria, Australia
| | - Tzu-Ching Meng
- Institute of Biochemical Sciences, National Taiwan University, and Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Tony Tiganis
- Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.,Department of Biochemistry & Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Helena E Richardson
- Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.,Department of Biochemistry & Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia.,Peter MacCallum Department of Oncology, University of Melbourne, Victoria, Australia.,Department of Biochemistry & Molecular Biology, University of Melbourne, Victoria, Australia.,Department of Anatomy & Neuroscience, University of Melbourne, Victoria, Australia
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7
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Carrig S, Bijjiga E, Wopat MJ, Martino AT. Insulin Therapy Improves Adeno-Associated Virus Transduction of Liver and Skeletal Muscle in Mice and Cultured Cells. Hum Gene Ther 2016; 27:892-905. [PMID: 27358030 DOI: 10.1089/hum.2016.073] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Adeno-associated virus (AAV) gene transfer is a promising treatment for genetic abnormalities. Optimal AAV vectors are showing success in clinical trials. Gene transfer to skeletal muscle and liver is being explored as a potential therapy for some conditions, that is, α1-antitrypsin (AAT) disorder and hemophilia B. Exploring approaches that enhance transduction of liver and skeletal muscle, using these vectors, is beneficial for gene therapy. Regulating hormones as an approach to improve AAV transduction is largely unexplored. In this study we tested whether insulin therapy improves liver and skeletal muscle gene transfer. In vitro studies demonstrated that the temporary coadministration (2, 8, and 24 hr) of insulin significantly improves AAV2-CMV-LacZ transduction of cultured liver cells and differentiated myofibers, but not of lung cells. In addition, there was a dose response related to this improved transduction. Interestingly, when insulin was not coadministered with the virus but given 24 hr afterward, there was no increase in the transgene product. Insulin receptor gene (INSR) expression levels were increased 5- to 13-fold in cultured liver cells and differentiated myofibers when compared with lung cells. Similar INSR gene expression profiles occurred in mouse tissues. Insulin therapy was performed in mice, using a subcutaneously implanted insulin pellet or a high-carbohydrate diet. Insulin treatment began just before intramuscular delivery of AAV1-CMV-schFIX or liver-directed delivery of AAV8-CMV-schFIX and continued for 28 days. Both insulin augmentation therapies improved skeletal muscle- and liver-directed gene transduction in mice as seen by a 3.0- to 4.5-fold increase in human factor IX (hFIX) levels. The improvement was observed even after the insulin therapy ended. Monitoring insulin showed that insulin levels increased during the brief period of rAAV delivery and during the entire insulin augmentation period (28 days). This study demonstrates that AAV transduction of liver or skeletal muscle can be improved by insulin therapy.
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Affiliation(s)
- Sean Carrig
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University , Queens, New York
| | - Enoch Bijjiga
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University , Queens, New York
| | - Mitchell J Wopat
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University , Queens, New York
| | - Ashley T Martino
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University , Queens, New York
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Cook JR, Langlet F, Kido Y, Accili D. Pathogenesis of selective insulin resistance in isolated hepatocytes. J Biol Chem 2015; 290:13972-80. [PMID: 25873396 DOI: 10.1074/jbc.m115.638197] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Indexed: 12/21/2022] Open
Abstract
The development of insulin resistance (IR) in the liver is a key pathophysiologic event in the development of type 2 diabetes. Although insulin loses its ability to suppress glucose production, it largely retains its capacity to drive lipogenesis. This selective IR results in the characteristic hyperglycemia and dyslipidemia of type 2 diabetes. The delineation of two branched pathways of insulin receptor (InsR) signaling to glucose versus triglyceride production, one through FoxO and the other through SREBP-1c, provides a mechanism to account for this pathophysiological abnormality. We tested the complementary hypothesis that selective IR arises due to different intrinsic sensitivities of glucose production versus de novo lipogenesis to insulin as a result of cell-autonomous down-regulation of InsR number in response to chronic hyperinsulinemia. We demonstrate in mouse primary hepatocytes that chronic hyperinsulinemia abrogates insulin's inhibition of glucose production, but not its stimulation of de novo lipogenesis. Using a competitive inhibitor of InsR, we show that there is a 4-fold difference between levels of InsR inhibition required to cause resistance of glucose production versus lipogenesis to the actions of insulin. Our data support a parsimonious model in which differential InsR activation underlies the selective IR of glucose production relative to lipogenesis, but both processes require signaling through Akt1/2.
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Affiliation(s)
- Joshua R Cook
- From the Department of Medicine, Columbia University, New York, New York 10032 and
| | - Fanny Langlet
- From the Department of Medicine, Columbia University, New York, New York 10032 and
| | - Yoshiaki Kido
- the Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Domenico Accili
- From the Department of Medicine, Columbia University, New York, New York 10032 and
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9
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Bhattacharya S, Ghosh R, Maiti S, Khan GA, Sinha AK. The activation by glucose of liver membrane nitric oxide synthase in the synthesis and translocation of glucose transporter-4 in the production of insulin in the mice hepatocytes. PLoS One 2013; 8:e81935. [PMID: 24349154 PMCID: PMC3861535 DOI: 10.1371/journal.pone.0081935] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 10/25/2013] [Indexed: 12/23/2022] Open
Abstract
Introduction Glucose has been reported to have an essential role in the synthesis and secretion of insulin in hepatocytes. As the efflux of glucose is facilitated from the liver cells into the circulation, the mechanism of transportation of glucose into the hepatocytes for the synthesis of insulin was investigated. Methods Grated liver suspension (GLS) was prepared by grating intact liver from adult mice by using a grater. Nitric oxide (NO) was measured by methemoglobin method. Glucose transporter-4 (Glut-4) was measured by immunoblot technique using Glut-4 antibody. Results Incubation of GLS with different amounts of glucose resulted in the uptake of glucose by the suspension with increased NO synthesis due to the stimulation of a glucose activated nitric oxide synthase that was present in the liver membrane. The inhibition of glucose induced NO synthesis resulted in the inhibition of glucose uptake. Glucose at 0.02M that maximally increased NO synthesis in the hepatocytes led to the translocation and increased synthesis of Glut-4 by 3.3 fold over the control that was inhibited by the inhibition of NO synthesis. The glucose induced NO synthesis was also found to result in the synthesis of insulin, in the presence of glucose due to the expression of both proinsulin genes I and II in the liver cells. Conclusion It was concluded that glucose itself facilitated its own transportation in the liver cells both via Glut-4 and by the synthesis of NO which had an essential role for insulin synthesis in the presence of glucose in these cells.
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Affiliation(s)
- Suman Bhattacharya
- Department of Biochemistry, Sinha Institute of Medical Science and Technology, Kolkata, India
- Department of Biochemistry, Vidyasagar University, Midnapore, India
| | - Rajeshwary Ghosh
- Department of Biochemistry, Sinha Institute of Medical Science and Technology, Kolkata, India
| | - Smarajit Maiti
- Department of Biochemistry, Vidyasagar University, Midnapore, India
| | - Gausal Azam Khan
- Department of Biochemistry, Sinha Institute of Medical Science and Technology, Kolkata, India
| | - Asru K. Sinha
- Department of Biochemistry, Sinha Institute of Medical Science and Technology, Kolkata, India
- * E-mail:
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Goustin AS, Derar N, Abou-Samra AB. Ahsg-fetuin blocks the metabolic arm of insulin action through its interaction with the 95-kD β-subunit of the insulin receptor. Cell Signal 2013; 25:981-8. [PMID: 23314177 DOI: 10.1016/j.cellsig.2012.12.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 11/10/2012] [Accepted: 12/19/2012] [Indexed: 12/22/2022]
Abstract
We previously have shown that Ahsg, a liver glycoprotein, inhibits insulin receptor (InsR) tyrosine kinase (TK) activity and the ERK1/2 mitogenic signaling arm of insulin signaling. Here we show that Ahsg blocks insulin-stimulated GLUT4 translocation and Akt activation in intact cells (mouse myoblasts). Furthermore, Ahsg inhibits InsR autophosphorylation of highly-purified insulin holoreceptors in a cell-free, ATP-dependent system, with an IC50 within the range of single-chain Ahsg concentrations in human serum. Binding of (125)I-insulin to living cells overexpressing the InsR shows a dissociation constant (KD) of 250pM, unaltered in the presence of 300 nM Ahsg. A mutant InsR cDNA encoding the signal peptide, the β-subunit and the furin processing site, but deleting the α-subunit, was stably expressed in HEK293 cells. Treatment with peroxovanadate, but not insulin, dramatically increased the 95 kD β-subunit tyrosine phosphoryation. The level of tyrosine phosphorylation of the 95-kD β-subunit can be driven down sharply by treatment of living HEK293 transfectant cells with physiological doses of Ahsg. Treatment of myogenic cells with Ahsg blunts insulin-stimulated InsR autophosphorylation and AKT phosphorylation. Taken together, we show that Ahsg antagonizes the metabolic functions initiated by InsR activation without interference in insulin binding. The experiments suggest a direct interaction of Ahsg with the InsR ectodomain β-subunit in a mode that does not significantly alter the high-affinity binding of insulin to the holoreceptor's two complementing α-subunits.
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Affiliation(s)
- Anton Scott Goustin
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Wayne State University School of Medicine, Detroit, MI, USA.
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Ghosh R, Karmohapatra SK, Bhattacharya G, Kumar Sinha A. The glucose-induced synthesis of insulin in liver. Endocrine 2010; 38:294-302. [PMID: 20972731 DOI: 10.1007/s12020-010-9388-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 08/20/2010] [Indexed: 01/13/2023]
Abstract
Pancreatic β cells, stimulated by glucose, are known to synthesize and secrete insulin. As liver diseases are reported to cause diabetes mellitus, studies were conducted to determine the possibility of glucose-induced insulin synthesis in the liver cells. The glucose-induced insulin synthesis was determined by in vitro translation of mRNA from the hepatocytes. The cDNA from mRNA was prepared and sequence analysis was performed. Incubation of hepatocytes from the liver of adult mice (n=10) with glucose (0.02 M) resulted in the insulin synthesis [0.03 (mean)±0.006 (S.D.) μunits/mg/h] compared to the pancreatic β cells [0.04±0.004 μunits/mg/h]. Immunohistochemical study also demonstrated the glucose-induced synthesis of insulin in liver cells. Incubation of the mice hepatocytes with glucose resulted in the synthesis of insulin mRNA. The purified mRNA which was used to prepare cDNA resulted in the formation of proinsulin I and proinsulin II genes corresponding to 182 and 188 base pairs, respectively. Sequence analysis of the cDNA indicated that proinsulin I as well as proinsulin II gene could be involved in the synthesis of insulin by hepatocytes. These results suggested that insulin synthesis in both hepatic and pancreatic cells could be involved in the control of diabetes mellitus.
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Affiliation(s)
- Rajeshwary Ghosh
- Sinha Institute of Medical Science and Technology, 288, Kendua Main Road, Garia, Calcutta, 700 084, India
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12
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Balbis A, Baquiran G, Bergeron JJ, Posner BI. Compartmentalization and insulin-induced translocations of insulin receptor substrates, phosphatidylinositol 3-kinase, and protein kinase B in rat liver. Endocrinology 2000; 141:4041-9. [PMID: 11089534 DOI: 10.1210/endo.141.11.7774] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Physiological doses of insulin in rats resulted in a rapid redistribution of key signaling proteins between subcellular compartments in rat liver. In plasma membranes (PM) and microsomes, insulin induced a rapid decrease in insulin receptor substrate-1/2 (IRS1/2) within 30 sec and an increase in these proteins in endosomes (EN) and cytosol. The level of p85 in PM increased 2.3-fold at 30 sec after insulin stimulation followed by a decrease at 2 min. In this interval, 60-85% and 10-20% of p85 in PM was associated with IRS1 and IRS2, respectively. Thus, in PM, IRS1/2 accounts for almost all of the protein involved in phosphatidylinositol 3-kinase activation. In ENs insulin induced a maximal increase of 40% in p85 recruitment. As in PM, almost all p85 was associated with IRS1/2. The greater level of p85 recruitment to PM was associated with a higher level of insulin-induced recruitment of Akt1 to this compartment (4.0-fold in PM vs. 2.4-fold in EN). There was a close correlation between Akt1 activity and Akt1 phosphorylation at Thr308 and Ser473 in PM and cytosol. However, in ENs the level of Akt1 activity per unit of phosphorylated Akt1 was significantly greater than in PM, indicating that in addition to phosphorylation, another factor(s) modulates Akt1 activation by insulin in rat liver. Our results demonstrate that activation of the insulin receptor kinase and modulation of key components of the insulin signaling cascade occur at the cell surface and within the endosomal system. These data provide further support for the role of the endocytic process in cell signaling.
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Affiliation(s)
- A Balbis
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec, Canada
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Sasaoka T, Wada T, Ishihara H, Takata Y, Haruta T, Usui I, Ishiki M, Kobayashi M. Synergistic role of the phosphatidylinositol 3-kinase and mitogen-activated protein kinase cascade in the regulation of insulin receptor trafficking. Endocrinology 1999; 140:3826-34. [PMID: 10433244 DOI: 10.1210/endo.140.8.6904] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To examine the molecular mechanism of insulin receptor trafficking, we investigated the intracellular signaling molecules that regulate this process in Rat1 fibroblasts overexpressing insulin receptors. Cellular localization of insulin receptors was assessed by confocal laser microscopy with indirect immunofluorescence staining. Insulin receptors were visualized diffusely in the basal state. Insulin treatment induced the change of insulin receptor localization to perinuclear compartment. This insulin-induced insulin receptor trafficking was not affected by treatment of the cells with PI3-kinase inhibitor (wortmannin), whereas treatment with MEK [mitogen-activated protein (MAP) kinase-Erk kinase] inhibitor (PD98059) partly inhibited the process in a dose-dependent manner. Interestingly, treatment with both wortmannin and PD98059 almost completely inhibited insulin receptor trafficking. The functional importance of PI3-kinase and MAP kinase in the trafficking process was directly assessed by using single cell microinjection analysis. Microinjection of p85-SH2 and/or catalytically inactive MAP kinase ([K71A]Erk1) GST fusion protein gave the same results as treatment with wortmannin and PD98059. Furthermore, to determine the crucial step for the requirement of PI3-kinase and MAP kinase pathways, the effect of wortmannin and PD98059 on insulin receptor endocytosis was studied. Insulin internalization from the plasma membrane and subsequent insulin degradation were not affected by treatment with wortmannin and PD98059. In contrast, insulin receptor down-regulation from the cell surface and insulin receptor degradation, after prolonged incubation with insulin, were markedly impaired by the treatment. These results suggest that PI3-kinase and MAP kinase pathways synergistically regulate insulin receptor trafficking at a step subsequent to the receptor internalization.
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Affiliation(s)
- T Sasaoka
- First Department of Medicine, Toyama Medical & Pharmaceutical University, Japan.
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Sanchez-Casas P, Yusta B, Blazquez E. Insulin-Induced Proteolysis of the Insulin Receptor alpha-Subunit from Rat Liver does not Occur in vivo but is Prevented in vitro by Blood Serum Proteinase Inhibitors. ACTA ACUST UNITED AC 1995. [DOI: 10.1111/j.1432-1033.1995.tb20869.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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15
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Chun M, Lin HY, Henis YI, Lodish HF. Endothelin-induced endocytosis of cell surface ETA receptors. Endothelin remains intact and bound to the ETA receptor. J Biol Chem 1995; 270:10855-60. [PMID: 7738024 DOI: 10.1074/jbc.270.18.10855] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We demonstrate unusual features of the intracellular processing of endothelin-1 (ET-1) and its receptor ETA, the receptor subtype that mediates contraction of vascular smooth muscle cells. First, we show that in stably transfected CHO cells expressing ETA, binding of an ET-1 ligand induces rapid endocytosis of cell surface ETA. Receptor endocytosis was measured both by immunofluorescence and by radioiodinated antibodies specific for ETA. Second, we demonstrate that ET-1 remains intact for up to 2 h after endocytosis and, as judged by co-immunoprecipitation, internalized 125I-ET-1 remains bound to ETA receptors. We hypothesize that internalized ET-1, bound to ETA receptors, continues to activate a signal-transducing G protein, thus accounting for the prolonged period of contraction induced in smooth muscle cells by a single administration of ET-1.
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Affiliation(s)
- M Chun
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA
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16
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Kublaoui B, Lee J, Pilch PF. Dynamics of signaling during insulin-stimulated endocytosis of its receptor in adipocytes. J Biol Chem 1995; 270:59-65. [PMID: 7814420 DOI: 10.1074/jbc.270.1.59] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Insulin causes rapid insulin receptor autophosphorylation, receptor endocytosis, and phosphorylation of its principle substrate (IRS-1). Using rat adipocytes, we studied the dynamics of receptor autophosphorylation, the kinase activity, and the IRS-1 phosphorylation state relative to the subcellular localization of these proteins. After 2 min of insulin exposure, the specific phosphotyrosine content of the insulin receptor in the internal membranes (IM) peaks at a level 5-6-fold higher than the plasma membrane (PM) receptor and then declines after 5-8 min to a level similar to the PM receptor. The exogenous kinase activity of these receptors exactly mirrored their phosphotyrosine content. The distribution of IRS-1 is 80% cytosolic, 20% IM-associated, and essentially undetectable in the PM. The phosphorylation state of IRS-1 in the IM parallels that of the insulin receptor, but cytosolic IRS-1 phosphorylation remains constant. Insulin-dependent GLUT4 translocation to the PM occurs after the peak of IRS-1 phosphorylation. The data are consistent with the hypothesis that insulin action may be mediated by receptor internalization and interaction with its substrate(s) associated with internal membranes. A small fraction of phosphorylated insulin receptors is sufficient for signal transduction. The dephosphorylation of the insulin receptor and IRS-1 in the IM appears to be a concerted process, possibly mediated by the same enzyme.
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Affiliation(s)
- B Kublaoui
- Department of Biochemistry, Boston University School of Medicine, Massachusetts 02118
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17
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Carpentier JL. Insulin receptor internalization: molecular mechanisms and physiopathological implications. Diabetologia 1994; 37 Suppl 2:S117-24. [PMID: 7821727 DOI: 10.1007/bf00400835] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The initial interaction between insulin and its receptor on target cell surface is followed by a series of surface and intracellular steps which participate in the control of insulin action. Abnormalities of any of these steps could result in mishandling of the receptor leading to defective modulation of receptor number on the cell surface and to inappropriate cell sensitivity to the hormone. Thus, the identification of each of these steps as well as understanding the mechanisms governing them is obligatory to unravel some aspects of the pathogenesis of insulin resistance states. This was the goal of the studies we have carried out during recent years using combined molecular and cellular biology as well as biochemical techniques. These studies allowed us to propose the following ordered sequence of events: 1) insulin binds to receptors preferentially associated with microvilli on the cell surface; 2) insulin triggers receptor kinase activation and autophosphorylation which not only results in initiation of the various biological signals leading to insulin action but also in redistribution of the hormone-receptor complex in the plane of the membrane; 3) on the non-villous domain of the cell surface, insulin receptors anchor to clathrin-coated pits through specific "internalization sequences" present in their cytoplasmic juxtamembrane domain; 4) insulin-receptor complexes are internalized together with other receptors present in the same clathrin-coated pits through the formation of clathrin-coated vesicles; 5) the complexes are delivered to endosomes, the acidic pH of which induces the dissociation of insulin molecules from insulin receptors and their sorting in different directions; 6) insulin molecules are targetted to late endosomes and lysosomes where they are degraded; 7) receptors are recycled back to the cell surface in order to be reused.
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Affiliation(s)
- J L Carpentier
- Department of Morphology, University of Geneva, Switzerland
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18
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Carpentier JL. Robert Feulgen Prize Lecture 1993. The journey of the insulin receptor into the cell: from cellular biology to pathophysiology. HISTOCHEMISTRY 1993; 100:169-84. [PMID: 8244769 DOI: 10.1007/bf00269090] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The data that we have reviewed indicate that insulin binds to a specific cell-surface receptor. The complex then becomes involved in a series of steps which lead the insulin-receptor complex to be internalized and rapidly delivered to endosomes. From this sorting station, the hormone is targeted to lysosomes to be degraded while the receptor is recycled back to the cell surface. This sequence of events presents two degrees of ligand specificity: (a) The first step is ligand-dependent and requires insulin-induced receptor phosphorylation of specific tyrosine residues. It consists in the surface redistribution of the receptor from microvilli where it preferentially localizes in its unoccupied form. (b) The second step is more general and consists in the association with clathrin-coated pits which represents the internalization gate common to many receptors. This sequence of events participates in the regulation of the biological action of the hormone and can thus be implicated in the pathophysiology of diabetes mellitus and various extreme insulin resistance syndromes, including type A extreme insulin resistance, leprechaunism, and Rabson-Mendehall syndrome. Alterations of the internalization process can result either from intrinsic abnormalities of the receptor or from more general alteration of the plasma membrane or of the cell metabolism. Type I diabetes is an example of the latter possibility, since general impairment of endocytosis could contribute to extracellular matrix accumulation and to an increase in blood cholesterol. Thus, better characterization of the molecular and cellular biology of the insulin receptor and of its journey inside the cell definitely leads to better understanding of disease states, including diabetes.
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Affiliation(s)
- J L Carpentier
- Department of Morphology, University of Geneva, Switzerland
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19
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Naka D, Shimomura T, Yoshiyama Y, Sato M, Sato M, Ishii T, Hara H. Internalization and degradation of hepatocyte growth factor in hepatocytes with down-regulation of the receptor/c-Met. FEBS Lett 1993; 329:147-52. [PMID: 8394828 DOI: 10.1016/0014-5793(93)80212-d] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Hepatocyte growth factor (HGF) promotes proliferation of cultured hepatocytes by its interaction with cell surface receptors. In this paper, we examined the metabolic fate of HGF using hepatocytes. Kinetic analysis using [125I]HGF showed that 40% of surface-bound HGF was rapidly internalized in hepatocytes within 30 min at 37 degrees C. Under these conditions, the amount of HGF-bound c-Met, the high-affinity receptor, decreased from the cell surface. Furthermore, the internalized HGF was degraded and released from the cells. These results indicate that cell surface-bound HGF is internalized and degraded by the receptors, including c-Met, on hepatocytes.
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Affiliation(s)
- D Naka
- Biosciences Laboratory, Mitsubishi Kasei Corporation Research Center, Yokohama, Japan
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20
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Abstract
Like many other cell surface receptors for nutrients and polypeptide hormones, the insulin receptor undergoes a complex endocytotic itinerary. Upon insulin binding, the receptor is activated as a tyrosine-specific protein kinase and autophosphorylates. This autophosphorylation is necessary for the receptor to internalize. After endocytosis, the ligand (insulin) and its receptor are dissociated. Most of the insulin is degraded, whereas the receptors are largely recycled to the cell surface. The signals in the receptor that control and specify its endocytotic pathway are beginning to be understood. Through the techniques of in vitro mutagenesis, noninternalizing receptors have been engineered and their structural and functional properties have been analyzed. For example, the immediate submembranous domain of the insulin receptor has been found to contain sequences (Gly-Pro-Leu-Tyr and, to a lesser extent, Asn-Pro-Gln-Tyr) that are necessary for normal endocytosis. Receptors deleted or mutated in these sequences retain tyrosine kinase activity but fail to undergo endocytosis. Unlike the better understood low density lipoprotein and transferrin receptors, however, these sequences are not sufficient for endocytosis. An insulin receptor with only these sequences exposed in the cytoplasm does not internalize. Tyrosine kinase activity is thought to be needed to lead to autophosphorylation and a conformational change that exposes the otherwise buried endocytosis sequences in the normally dimerized insulin receptor. Non-internalizing mutants of the insulin receptor have been used to examine the role of endocytosis in insulin action. It was found that an endocytosis-defective receptor could induce a short-term metabolic action of insulin (glycogen synthetase stimulation) as well as longer-term mitogenic effects of insulin. Furthermore, insulin action deactivated after the hormone was removed from the noninternalizing receptors. Apparently, endocytosis is not necessary for insulin action, but probably is important for removing the insulin from the cell so the target cell for insulin responds in a time-limited fashion to the hormone.
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Affiliation(s)
- D A McClain
- Veterans Administration Medical Center, Birmingham, Alabama 35213
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21
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Knutson VP. Ligand-independent internalization and recycling of the insulin receptor. Effects of chronic treatment of 3T3-C2 fibroblasts with insulin and dexamethasone. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)48374-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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22
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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
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23
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Sato H, Terasaki T, Mizuguchi H, Okumura K, Tsuji A. Receptor-recycling model of clearance and distribution of insulin in the perfused mouse liver. Diabetologia 1991; 34:613-21. [PMID: 1955094 DOI: 10.1007/bf00400989] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
After perfusion of mouse livers with A14-125I-insulin for designated intervals, an acid-wash technique was employed to separately measure the surface-bound (Xs) and intracellular (Xi) A14-125I-insulin, as well as intracellular degradation products (Xdeg) of labelled insulin. From the perfusate concentrations (Cp) of A14-125I-insulin, the apparent intrinsic hepatic clearance of labelled insulin at a high dose (0.2 nmol/l) was shown to be 60% smaller than that at a low dose (0.018 nmol/l), indicating that the cellular uptake of insulin is remarkably nonlinear at the concentration range examined. From the time courses of Cp, Xs, Xi and Xdeg, the hepatic insulin disposition was shown to be largely accounted for by the receptor-mediated endocytosis. The observed data at the low dose were analysed to estimate biochemical parameters, (i.e., total receptor number, endocytotic rate constant and intracellular degradation rate constant) according to "receptor-recycling" and "non-receptor-recycling" models, using a computer-aided optimization procedure. The "receptor-recycling" model could not only adequately explain the Cp, Xs, Xi and Xdeg at the low dose, but also predict the Cp at the high dose. On the other hand, a "non-receptor-recycling" model, in which recycling of receptors was not assumed, could also explain the observed data at the low dose, but failed to predict the Cp at the high dose, indicating that the receptor recycling process is necessary to explain the hepatic insulin clearance at high insulin concentrations, at which hepatic insulin clearance should be limited by the rate of receptor recycling.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H Sato
- Faculty of Pharmaceutical Sciences, Kanazawa University, Japan
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24
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Childs GV, Westlund KN, Tibolt RE, Lloyd JM. Hypothalamic regulatory peptides and their receptors: cytochemical studies of their role in regulation at the adenohypophyseal level. JOURNAL OF ELECTRON MICROSCOPY TECHNIQUE 1991; 19:21-41. [PMID: 1660066 DOI: 10.1002/jemt.1060190104] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Hypothalamic regulatory peptides bind to specific receptors on target cells in the pituitary and control secretion. They in turn can be regulated at the pituitary level by steroid and peptide modulators. Affinity cytochemical techniques are important tools for the identification of specific target binding sites for these regulatory peptides. This presentation reviews the work in which potent, biotinylated ligands of gonadotropin releasing hormone (bio-GnRH), corticotropin releasing hormone (bio-CRH), and arginine vasopressin (bio-AVP) were applied to study the target cell responses. Bio-GnRH, bio-CRH, and bio-AVP bind to membrane receptors on specific anterior pituitary cells. Dual labeling for either gonadotropin or adrenocorticotropin (ACTH) antigens further identified the target cells. After 1-3 minutes, the label was in patches or capped on the surface. After 3 minutes, it was internalized in small vesicles and sent to receptosomes and vacuoles in the Golgi complex. Eventually the biotinylated peptides, or a metabolite, was found in the lysosomes (multivesicular bodies) and a subpopulation of secretory granules. The route and rate of uptake was similar to that described for the classical receptor-mediated endocytosis process. In contrast, intermediate lobe corticotropes internalized the bio-CRH in less than 1 minute. The route through the Golgi complex appeared to be bypassed. Instead the labeled peptide was in vesicles, on the membranes of scattered vacuoles, and in multivesicular bodies. Modulation of ligand binding by steroids showed that changes in receptor numbers correlated with changes in the number of cells that bound the ligand. In male rats, dihydrotestosterone reduced the percentage of GnRH-bound cells by 50%. Most of the reduction appeared in cells that stored luteinizing hormone (LH) antigens. In diestrous female rats, estradiol increased the percentage of bio-GnRH-bound cells. However, the steroid decreased the percentage of GnRH-bound cells in cells from proestrous rats. Glucocorticoids decreased the percentage of CRH-bound corticotropes in as little as 10 minutes. Potentiation of secretion by these ligands was correlated with increases in the percentage of ligand-bound cells. AVP pretreatment of corticotropes increased the percentage of cells that bound bio-CRH. It also increased the rate of receptor-mediated endocytosis of CRH and changed the route so that the Golgi complex was bypassed. This effect could be mimicked by activation of its second messengers (calcium and protein kinase C). Similarly, CRH pretreatment increased the percentage of corticotropes that bound AVP. Thyrotropin releasing hormone (TRH) pretreatment also increased the percentage of thyrotropes that bound AVP.(ABSTRACT TRUNCATED AT 400 WORDS)
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MESH Headings
- Animals
- Arginine Vasopressin/metabolism
- Immunohistochemistry
- Neuropeptides/metabolism
- Pituitary Gland, Anterior/metabolism
- Pituitary Gland, Anterior/ultrastructure
- Pituitary Hormone-Releasing Hormones/metabolism
- Receptors, Angiotensin/metabolism
- Receptors, Angiotensin/ultrastructure
- Receptors, Corticotropin-Releasing Hormone
- Receptors, LHRH/metabolism
- Receptors, LHRH/ultrastructure
- Receptors, Neurotransmitter/metabolism
- Receptors, Neurotransmitter/ultrastructure
- Receptors, Vasopressin
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Affiliation(s)
- G V Childs
- Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77550
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25
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Down-regulation and recycling of high affinity cholecystokinin receptors on pancreatic acinar cells. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)99237-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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26
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A cluster of four Sp1 binding sites required for efficient expression of the human insulin receptor gene. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(19)67884-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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27
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Kamio T, Shigematsu K, Kawai K, Tsuchiyama H. Immunoreactivity and receptor expression of insulinlike growth factor I and insulin in human adrenal tumors. An immunohistochemical study of 94 cases. THE AMERICAN JOURNAL OF PATHOLOGY 1991; 138:83-91. [PMID: 1702931 PMCID: PMC1886050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Using immunoperoxidase methods, 94 human adrenal tumors were examined for evidence of immunoreactivity and receptor expression of insulinlike growth factor I (IGF-I) and insulin. The frequency of IGF-I in adrenocortical carcinomas was significantly higher than that in adenomas of the adrenal glands. The adrenocortical carcinomas showed strong intensity of staining for IGF-I, IGF-I receptors, and insulin receptors. A significant correlation between immunoreactivity and receptor expression of both IGF-I and insulin was found only in the adrenocortical carcinomas. The adrenocortical adenomas with Cushing's syndrome and pheochromocytomas, more than adrenocortical adenomas with Conn's syndrome, also stained strongly for insulin receptors. Thus the IGF-I and insulin probably play a role in the growth of adrenocortical carcinoma tissues, possibly through autocrine mechanisms. The expression of insulin receptors in adrenocortical adenomas in the presence of Cushing's syndrome and pheochromocytomas may be associated with functions.
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Affiliation(s)
- T Kamio
- Second Department of Pathology, Nagasaki University School of Medicine, Japan
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28
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Wang JJ, Chang JP, Teng CS. Immunocytochemical demonstration of the binding and internalization of growth hormone in GERL of Chang hepatoma cells. Cell Tissue Res 1990; 262:273-81. [PMID: 2076535 DOI: 10.1007/bf00309882] [Citation(s) in RCA: 4] [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 binding and internalization of endogenous growth hormone in Chang hepatoma cells were localized on the cell surface and in the Golgi-endoplasmic reticulum-lysosome (GERL) area by various indirect immunocytochemical labeling techniques, namely, peroxidase or colloidal gold conjugated to secondary antibody, and avidin-biotin complex methods. Rabbit antiserum and monoclonal antibodies raised against HPLC-purified porcine growth hormone were used in this study. In fixed material, antigen-antibody complexes were found to be homogeneously distributed along the cell membrane. Control groups showed negative binding on the cell surface. Trypsin treatment before immunolabeling removed antibody binding completely, but hyaluronidase was ineffective. Pretreatment of lectins did not block the recognition of primary antibody to antigen molecules on cell surface. Internalization of the antigen-antibody peroxidase or gold complexes was demonstrated in the cells, which were immunolabeled at 4 degrees C, and then reincubated for 0-30 min at 37 degrees C before fixation. After reincubation, the internalized ligand complexes were found in vesicles near the cell surface or in the GERL area near the Golgi apparatus which, however, did not label for peroxidase. These findings suggest that the trypsin-sensitive growth hormone, specifically bound and internalized into Chang hepatoma cells, is localized in the GERL instead of the Golgi apparatus and might be involved in the mechanism of tumor cell growth.
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Affiliation(s)
- J J Wang
- Department of Biology and Anatomy, National Defense Medical Center, Taipei, Taiwan, Republic of China
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29
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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.
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Affiliation(s)
- J R Levy
- Department of Medicine, Hunter Holmes McGuire Veterans Administration Medical Center, Richmond, Virginia
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30
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Jones AL, Burwen SJ. Pathways and Functions of Biliary Protein Secretion. Compr Physiol 1989. [DOI: 10.1002/cphy.cp060332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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31
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Rosselin G. Liver Receptors for Regulatory Peptides. Compr Physiol 1989. [DOI: 10.1002/cphy.cp060212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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32
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Abstract
Following initial binding to specific cell surface receptors insulin is internalized in target cells. The fate of the internalized insulin-receptor complexes and how the processes involved are regulated is reviewed. The implications of these events in the effects of insulin on its target cells and in the physiopathology of diabetes and insulin resistance states are also considered.
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Affiliation(s)
- J L Carpentier
- Institute of Histology and Embryology, University of Geneva, Switzerland
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33
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Kinetic Study of Internalization and Degradation of 131I-Labeled Follicle-stimulating Hormone in Mouse Sertoli Cells and Its Relevance to Other Systems. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)80043-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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34
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Lipson KE, Kolhatkar AA, Donner DB. Cell surface proteolysis and down-regulation of the hepatic insulin receptor. Evidence for selective sorting of intact and degraded receptors after internalization. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)81543-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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35
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Castrodad FA, Renaud FL, Ortiz J, Phillips DM. Biogenic amines stimulate regeneration of cilia in Tetrahymena thermophila. THE JOURNAL OF PROTOZOOLOGY 1988; 35:260-4. [PMID: 3397915 DOI: 10.1111/j.1550-7408.1988.tb04340.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Serotonin and catecholamines affect the regeneration of cilia in Tetrahymena thermophila in a dose-dependent manner: micromolar concentrations are stimulatory, whereas millimolar concentrations have little or no effect. This conclusion is based on motility measurements in regenerating cells and on ciliary counts in scanning electron micrographs. In addition, the recognition mechanism for each hormone appears to be specific and independent. Our results suggest an evolutionary link with hormonal mechanisms in multicellular eukaryotes.
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Affiliation(s)
- F A Castrodad
- Biology Department, Humacao University College, University of Puerto Rico
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36
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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
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37
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Jochen AL. Relationships between cell surface insulin binding and endocytosis in adipocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1988; 254:E365-71. [PMID: 3279812 DOI: 10.1152/ajpendo.1988.254.3.e365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Chymotrypsin substrate analogues, such as N-acetyl-Tyr ethyl ester, have recently been demonstrated to inhibit the endocytic uptake of insulin in isolated rat adipocytes. In this study, the effects of N-acetyl-Tyr ethyl ester on cell surface insulin binding and dissociation were examined. Surface-bound 125I-insulin was distinguished from intracellular 125I-insulin by the sensitivity of the former to rapid dissociation with an acidic buffer (pH 3.0). Plateau levels of surface-bound insulin at 37 degrees C were increased 70% by inhibiting the internalization pathway. This increase was temperature and insulin concentration dependent. Thus differences in surface binding were small at 12 degrees C and also at high (100-200 ng/ml) insulin concentrations. Inhibition of internalization with N-acetyl-Tyr ethyl ester markedly slowed the loss of surface-bound insulin observed during dissociation studies. After 20-30 min of dissociation, the remaining levels of surface-bound insulin were three- to fourfold higher in treated adipocytes compared with control adipocytes. Added unlabeled insulin retained its ability to accelerate the dissociation of insulin in N-acetyl-Tyr ethyl ester-treated cells. These observations indicate that the internalization pathway is a quantitatively important factor in determining levels of surface binding at 37 degrees C and in determining the rate of deactivation of insulin binding.
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Affiliation(s)
- A L Jochen
- Department of Medicine, Medical College of Wisconsin, Milwaukee 53226
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38
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Shibasaki Y, Sakura H, Odawara M, Shibuya M, Kanazawa Y, Akanuma Y, Takaku F, Kasuga M. Glucocorticoids increase insulin binding and the amount of insulin-receptor mRNA in human cultured lymphocytes. Biochem J 1988; 249:715-9. [PMID: 3281654 PMCID: PMC1148765 DOI: 10.1042/bj2490715] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The effect of steroid hormones on insulin binding and the amount of insulin-receptor mRNA was examined in IM-9 lymphocytes. Cortisol and cortexolone, but not oestrogen, increased both the binding of insulin and the amount of insulin-receptor mRNA in a time- and dose-dependent manner. Cortisol was most potent, and induced a 2-fold increase in insulin binding and a 4-fold increase in mRNA. The elevation in binding was due to an increased number of insulin receptors at the cell surface. The increase in mRNA involved all four of the insulin-receptor mRNAs and could not be inhibited by cycloheximide. The cortisol-induced increase in mRNA was associated with a 3-4-fold increase in the synthesis of pro-receptor. The relative potency of the three steroids indicated that these effects were mediated by an interaction with the glucocorticoid receptor. The results of this study suggest that cortisol can increase the number of insulin receptors at the cell surface by increasing the amounts of insulin-receptor mRNA and the synthesis de novo of insulin receptors.
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Affiliation(s)
- Y Shibasaki
- Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan
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39
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Schvartz I, Hazum E. Internalization and recycling of receptor-bound gonadotropin-releasing hormone agonist in pituitary gonadotropes. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)45489-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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40
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Quiñones-Maldonado V, Renaud FL. Effect of biogenic amines on phagocytosis in Tetrahymena thermophila. THE JOURNAL OF PROTOZOOLOGY 1987; 34:435-8. [PMID: 3430409 DOI: 10.1111/j.1550-7408.1987.tb03208.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Stimulation of phagocytosis by serotonin and catecholamines in Tetrahymena grown in proteose-peptone medium proved to be concentration dependent, the optimal concentrations being approximately 0.1 to 1.0 microM. The serotonergic antagonists, spiperone, and metergoline, also stimulated the process, whereas the beta- and alpha-adrenergic antagonists, propranolol, alprenolol, and ergocryptine, had no effect or inhibited phagocytosis. A wide variety of derivatives of the biogenic amines had no effect on phagocytosis, demonstrating the specificity of recognition mechanism for neurohormones in Tetrahymena. Such hormones act by at least two independent mechanisms, one for adrenergic agonists, another for dopamine. Presumably, recognition mechanisms for hormones in protozoa resemble in some respects those in multicellular organisms, therefore bespeaking a common origin.
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41
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Characterization of the promoter region of the human insulin receptor gene. Evidence for promoter activity. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)47714-9] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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42
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Soubigou P, Ali M, Plas C. Uncoupling between the insulin-receptor cycle and the cellular degradation of the hormone in cultured foetal hepatocytes. Effect of drugs and temperature that inhibit insulin degradation. Biochem J 1987; 246:567-73. [PMID: 3318811 PMCID: PMC1148318 DOI: 10.1042/bj2460567] [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: 01/05/2023]
Abstract
Sequential changes in the numbers of cell-surface receptors induced by a transitory exposure to insulin in cultured 18-day foetal-rat hepatocytes were investigated in the presence of drugs and at a temperature of 22 degrees C, which inhibit cellular insulin degradation. Chloroquine (70 microM) and monensin (3 microM) did not greatly change the initial rate of internalization of cell-surface receptor sites after exposure to 10 nM-insulin, but led to a steady state after 20 min, which represented 40% of the initial binding, compared with 5 min and 60% in the absence of the drug. Moreover, these drugs strongly decreased the proportion of receptor sites recovered at the cell surface after subsequent removal of the hormone. They were ineffective when insulin was not present. The removal of monensin together with the hormone allowed partial restoration of cell-surface receptor sites and degradation of cell-associated insulin to start again at the initial speed, indicating a reversible effect of the drug. During this phase, the drug concentration-dependence for the two effects showed that receptor recycling was restored with concentrations of monensin not as low as for insulin degradation. The effect of vinblastine (50-100 microM) was similar to that of chloroquine and monensin, whereas no modification in the internalization and recovery processes was observed in the presence of bacitracin concentrations (1-3 mM) that inhibit insulin degradation by 70%. A temperature of 22 degrees C did not prevent the receptor internalization, but had a slowing effect on the recycling process, which appeared to vary in experiments where insulin degradation remained inhibited. The present study shows that the process of insulin degradation mediated by receptor endocytosis is not a prerequisite for insulin-receptor recycling in cultured foetal hepatocytes.
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Affiliation(s)
- P Soubigou
- Laboratoire Interactions Cellulaires, U.E.R. Odontologie, Université Paris, France
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43
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Russell DS, Gherzi R, Johnson EL, Chou CK, Rosen OM. The protein-tyrosine kinase activity of the insulin receptor is necessary for insulin-mediated receptor down-regulation. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)60889-0] [Citation(s) in RCA: 120] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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44
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Blake AD, Hayes NS, Slater EE, Strader CD. Insulin receptor desensitization correlates with attenuation of tyrosine kinase activity, but not of receptor endocytosis. Biochem J 1987; 245:357-64. [PMID: 3311033 PMCID: PMC1148129 DOI: 10.1042/bj2450357] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A model of insulin-receptor down-regulation and desensitization has been developed and described. In this model, both insulin-receptor down-regulation and functional desensitization are induced in the human HepG2 cell line by a 16 h exposure of the cells to 0.1 microM-insulin. Insulin-receptor affinity is unchanged, but receptor number is decreased by 50%, as determined both by 125I-insulin binding and by protein immunoblotting with an antibody to the beta-subunit of the receptor. This down-regulation is accompanied by a disproportionate loss of insulin-stimulated glycogen synthesis, yielding a population of cell-surface insulin receptors which bind insulin normally but which are unable to mediate insulin-stimulated glycogen synthesis within the cell. Upon binding of insulin, the desensitized receptors are internalized rapidly, with characteristics indistinguishable from those of control cells. In contrast, this desensitization is accompanied by a loss of the insulin-sensitive tyrosine kinase activity of insulin receptors isolated from these cells. Receptors isolated from control cells show a 5-25-fold enhancement of autophosphorylation of the beta-subunit by insulin; this insulin-responsive autophosphorylation is severely attenuated after desensitization to a maximum of 0-2-fold stimulation by insulin. Likewise, the receptor-mediated phosphorylation of exogenous angiotensin II, which is stimulated 2-10-fold by insulin in receptors from control cells, is completely unresponsive to insulin in desensitized cells. These data provide evidence that the insulin-receptor tyrosine kinase activity correlates with insulin stimulation of an intracellular metabolic event. The data suggest that receptor endocytosis is not sufficient to mediate insulin's effects, and thereby argue for a role of the receptor tyrosine kinase activity in the mediation of insulin action.
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Affiliation(s)
- A D Blake
- Department of Biochemical Endocrinology, Merck Sharp & Dohme Research Laboratories, Rahway, NJ 07065
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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
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46
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Green MR, Mycock C, Smith CG, Couchman JR. Biochemical and ultrastructural processing of [125I]epidermal growth factor in rat epidermis and hair follicles: accumulation of nuclear label. J Invest Dermatol 1987; 88:259-65. [PMID: 3493301 DOI: 10.1111/1523-1747.ep12465488] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Although the intracellular ultrastructural processing of epidermal growth factor (EGF) and its receptor have been described in cell culture systems, very few studies have examined this phenomenon in intact tissues. We have examined the ultrastructural and biochemical handling of [125I]EGF in the epidermis and hair follicle bulb of intact, viable, 3- to 5-day-old rat skin the EGF receptor distribution of which has already been documented and in which EGF has been shown to be biologically active. After incubation of explants with 10 nM [125I]EGF for 2.5 h at 25 degrees or 37 degrees C, radiolabel was detected over the basal cells of the epidermis and hair follicle outer root sheath, confirming previous light microscope observations. More specifically, silver grains were observed near coated and uncoated plasma membrane and coated membrane invaginations, Golgi apparatus, lysosomal structures, and nuclei. Sodium azide inhibited internalization of label, whereas a series of lysosomal inhibitors (chloroquine, monensin, and iodoacetamide) caused a slight increase in silver grains associated with lysosomal vesicles and a decrease in nuclear label. Biochemical analysis indicated that greater than 35% of radioactivity following incubation at 37 degrees C was in the form of degraded [125I]EGF fragments and that inclusion of chloroquine, monensin, and iodoacetamide reduced this value to 20.8%, 8.6%, and 4.0%, respectively. In addition, chloramine T-prepared [125I]EGF was found to be covalently cross-linked with low efficiency to a protein having the molecular weight of the EGF receptor. These data are discussed in the light of the effects of EGF on epithelial cell proliferation in skin.
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Cousin JL, Samson M, Pilch PF, Fehlmann M. Internalization of insulin receptors and HLA antigens in human hepatoma cells. Biochem J 1987; 242:403-10. [PMID: 3036089 PMCID: PMC1147719 DOI: 10.1042/bj2420403] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Human HepG2 hepatoma cells express a high number of insulin receptors. Growing cells exhibit 70% of their insulin receptors on the plasma membrane. Moreover, cell-surface insulin receptors form molecular complexes with class I major histocompatibility antigens, as determined by co-immunoprecipitation of the receptors by anti-class I monoclonal antibodies. On exposure to saturating concentrations of insulin, the hormone is rapidly internalized into a Pronase-resistant compartment. Internalization of insulin is accompanied by a rapid (t1/2 = 2-3 min) redistribution of insulin receptors from the cell surface to an intracellular compartment. On removal of insulin from the medium, functional receptors recycle back to the plasma membrane, where they can bind insulin again. With chronic exposure of HepG2 cells to insulin, the initial redistribution of receptors is followed by a slow (t1/2 = 9 h) down-regulation of the receptors. Finally, notwithstanding their interaction at the cell surface, insulin receptors and class I major histocompatibility antigens are internalized at different rates and with independent regulation.
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Berhanu P, Saunders DJ, Brandenburg D. Adipocyte insulin receptor. Generation of a cryptic domain of the alpha-subunit during internalization of hormone-receptor complexes. Biochem J 1987; 242:589-96. [PMID: 3297047 PMCID: PMC1147745 DOI: 10.1042/bj2420589] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The dynamics of the internalization of photoaffinity-labelled insulin-receptor complexes was investigated in isolated rat adipocytes by using tryptic proteolysis to probe both the orientation and cellular location of the labelled complexes. In cells that were labelled at 16 degrees C and not prewarmed, 150 micrograms of trypsin/ml rapidly degraded the labelled 125 kDa insulin-receptor subunit into a major proteolytic fragment of 70 kDa and minor amounts of 90- and 50-kDa fragments. With milder trypsin treatment conditions (100 micrograms of trypsin/ml, 15 s at 37 degrees C), the 90 kDa peptide (different from the 90 kDa beta-subunit of the insulin receptor) appeared as a major intermediate proteolytic product, but this species was rapidly and completely converted into the 70- and 50-kDa fragments with continued exposure to trypsin, such that it did not accumulate to appreciable amounts in cells that were not prewarmed before trypsin exposure. By contrast, trypsin treatment of cells prewarmed to 37 degrees C for various times showed that: first, a proportion of the labelled 125 kDa receptors was internalized (became trypsin-insensitive); secondly, the 90 kDa tryptic peptide was formed in large amounts, with proportionate decreases occurring in the amounts of the 70- and 50-kDa tryptic peptides. The increased accumulation of the 90 kDa tryptic peptide from cells preincubated at 37 degrees C, but not at 16 degrees C, indicated that trypsin cleavage sites within the 90 kDa segment of the insulin-receptor alpha-subunit that were exposed at 16 degrees C were made inaccessible by incubation at 37 degrees C, a finding that is consistent with generation of a cryptic domain of the receptor subunit. The tryptic generation of the 90 kDa peptide at 37 degrees C was rapid, becoming half-maximal in 4.4 +/- 0.6 min and maximal in 15-20 min, preceded the intracellular accumulation of labelled receptors (half-maximal in 12.6 +/- 0.7 min and maximal in 30-40 min), was highly correlated with receptor internalization, and was not observed in cultured IM-9 lymphocytes, a cell line in which photolabelled insulin receptors are primarily lost by shedding into the incubation media. These results show that, in adipocytes incubated at 37 degrees C, rapid masking of a previously (at 16 degrees C) accessible domain of the insulin-receptor alpha-subunit occurs and that this dynamic process happens at an early stage in the internalization of insulin-receptor complexes.
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49
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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
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50
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Smith RM, Jarett L. Ultrastructural evidence for the accumulation of insulin in nuclei of intact 3T3-L1 adipocytes by an insulin-receptor mediated process. Proc Natl Acad Sci U S A 1987; 84:459-63. [PMID: 3540967 PMCID: PMC304227 DOI: 10.1073/pnas.84.2.459] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Monomeric ferritin-labeled insulin (Fm-Ins), a biologically active, electron-dense marker of occupied insulin receptors, was used to characterize the internalization of insulin in 3T3-L1 adipocytes. Fm-Ins bound specifically to insulin receptors and was internalized in a time- and temperature-dependent manner. Fm-Ins was found in cytoplasmic vesicles within 5-10 min at 37 degrees C and subsequently was observed in multivesicular bodies and lysosomes. In addition, small amounts of Fm-Ins were associated with nuclei after 30 min. The number of Fm-Ins particles observed in nuclei continued to increase in a time-dependent manner until at least 90 min. In the nucleus, several Fm-Ins particles usually were found in the same general location--near nuclear pores, associated with the periphery of the condensed chromatin. Addition of a 250-fold excess of unlabeled insulin or incubation at 15 degrees C reduced the number of Fm-Ins particles found in nuclei after 90 min by 99% or 92%, respectively. Nuclear accumulation of unlabeled ferritin was only 2% of that found with Fm-Ins after 90 min at 37 degrees C. Biochemical experiments utilizing 125I-labeled insulin and subcellular fractionation indicated that intact 3T3-L1 adipocytes internalized insulin rapidly and that approximately equal to 3% of the internalized ligand accumulated in nuclei after 1 hr. These data provide biochemical and high-resolution ultrastructural evidence that 3T3-L1 adipocytes accumulate potentially significant amounts of insulin in nuclei by an insulin receptor-mediated process. The transport of insulin or the insulin-receptor complex to nuclei in this cell or in others may be directly involved in the long-term biological effects of insulin--in particular, in the control of DNA and RNA synthesis.
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