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Coppola I, Brouwers B, Meulemans S, Ramos-Molina B, Creemers JWM. Differential Effects of Furin Deficiency on Insulin Receptor Processing and Glucose Control in Liver and Pancreatic β Cells of Mice. Int J Mol Sci 2021; 22:6344. [PMID: 34198511 PMCID: PMC8231939 DOI: 10.3390/ijms22126344] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 06/11/2021] [Accepted: 06/12/2021] [Indexed: 01/04/2023] Open
Abstract
The insulin receptor (IR) is critically involved in maintaining glucose homeostasis. It undergoes proteolytic cleavage by proprotein convertases, which is an essential step for its activation. The importance of the insulin receptor in liver is well established, but its role in pancreatic β cells is still controversial. In this study, we investigated the cleavage of the IR by the proprotein convertase FURIN in β cells and hepatocytes, and the contribution of the IR in pancreatic β cells and liver to glucose homeostasis. β-cell-specific Furin knockout (βFurKO) mice were glucose intolerant, but liver-specific Furin knockout (LFurKO) mice were normoglycemic. Processing of the IR was blocked in βFurKO cells, but unaffected in LFurKO mice. Most strikingly, glucose homeostasis in β-cell-specific IR knockout (βIRKO) mice was normal in younger mice (up to 20 weeks), and only mildly affected in older mice (24 weeks). In conclusion, FURIN cleaves the IR non-redundantly in β cells, but redundantly in liver. Furthermore, we demonstrated that the IR in β cells plays a limited role in glucose homeostasis.
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Affiliation(s)
- Ilaria Coppola
- Laboratory for Biochemical Neuroendocrinology, Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium; (I.C.); (B.B.); (S.M.)
| | - Bas Brouwers
- Laboratory for Biochemical Neuroendocrinology, Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium; (I.C.); (B.B.); (S.M.)
| | - Sandra Meulemans
- Laboratory for Biochemical Neuroendocrinology, Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium; (I.C.); (B.B.); (S.M.)
| | - Bruno Ramos-Molina
- Laboratory for Biochemical Neuroendocrinology, Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium; (I.C.); (B.B.); (S.M.)
- Obesity and Metabolism Group, Biomedical Research Institute of Murcia (IMIB-Arrixaca), 30120 Murcia, Spain
| | - John W. M. Creemers
- Laboratory for Biochemical Neuroendocrinology, Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium; (I.C.); (B.B.); (S.M.)
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2
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Bernot D, Stalin J, Stocker P, Bonardo B, Scroyen I, Alessi MC, Peiretti F. Plasminogen activator inhibitor 1 is an intracellular inhibitor of furin proprotein convertase. J Cell Sci 2011; 124:1224-30. [PMID: 21406565 DOI: 10.1242/jcs.079889] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Proprotein convertases (PCs) are a family of serine proteases that are involved in the post-translational processing and activation of a wide range of regulatory proteins. The upstream role of PCs in the control of many physiological and pathological processes generates a growing interest in understanding their regulation. Here, we demonstrate that the serine protease inhibitor plasminogen activator inhibitor 1 (PAI-1) forms an SDS-stable complex with the PC furin, which leads to the inhibition of the intra-Golgi activity of furin. It is known that elevated PAI-1 plasma levels are correlated with the occurrence of the metabolic syndrome and type 2 diabetes, and we show that PAI-1 reduces the furin-dependent maturation and activity of the insulin receptor and ADAM17: two proteins involved in the onset of these metabolic disorders. In addition to demonstrating that PAI-1 is an intracellular inhibitor of furin, this study also provides arguments in favor of an active role for PAI-1 in the development of metabolic disorders.
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Affiliation(s)
- Denis Bernot
- Inserm, U626, Université de Méditerranée, Faculté de Médecine, 27 Boulevard Jean Moulin, 13385 Marseilles Cedex 5, France
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3
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Wei W, Hackmann K, Xu H, Germino G, Qian F. Characterization of cis-autoproteolysis of polycystin-1, the product of human polycystic kidney disease 1 gene. J Biol Chem 2007; 282:21729-37. [PMID: 17525154 DOI: 10.1074/jbc.m703218200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Polycystin-1 (PC1), the PKD1 gene product, plays a critical role in renal tubule diameter control and disruption of its function causes cyst formation in human autosomal dominant polycystic kidney disease. Recent evidence shows that PC1 undergoes cleavage at the juxtamembrane G protein-coupled receptor proteolytic site (GPS), a process likely to be essential for its biological activity. Here we further characterized the proteolytic cleavage of PC1 at the GPS domain. We determined the actual cleavage site to be between leucine and threonine of the tripeptide HLT(3049) of human PC1. Cleavage occurs in the early intracellular secretory pathway and requires initial N-glycan attachment but not its subsequent trimming. We provide evidence that the cleavage occurs via a cis-autoproteolytic mechanism involving an ester intermediate as shown for Ntn hydrolases and EMR2.
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Affiliation(s)
- Wen Wei
- Division of Nephrology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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4
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Griffiths SL, Grainger DJ. Proposal of a novel diabetogenic mechanism involving the serpin PAI-1. Bioessays 2006; 28:629-41. [PMID: 16700057 DOI: 10.1002/bies.20418] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Metabolic Syndrome is a cluster of risk factors (including obesity, hypertension and insulin resistance), which is associated with late-onset diabetes and coronary heart disease. Elevated levels of the protease inhibitor PAI-1 are well-known molecular markers of the Metabolic Syndrome. Here, however, we present a hypothesis that PAI-1 acts as a causative factor in the development of Metabolic Syndrome and its clinical sequelae. We propose that PAI-1 inhibits the activity of members of the proprotein convertase (PC) class of serine proteases and that this underlies, at a molecular level, many of the other features of the Metabolic Syndrome cluster.
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5
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Kawashima Y, Kanzaki S, Yang F, Kinoshita T, Hanaki K, Nagaishi JI, Ohtsuka Y, Hisatome I, Ninomoya H, Nanba E, Fukushima T, Takahashi SI. Mutation at cleavage site of insulin-like growth factor receptor in a short-stature child born with intrauterine growth retardation. J Clin Endocrinol Metab 2005; 90:4679-87. [PMID: 15928254 DOI: 10.1210/jc.2004-1947] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Mouse knockout models have clearly demonstrated the critical importance of IGF-I and IGF receptor type 1 (IGF-IR) for embryonic growth as well as postnatal growth. OBJECTIVE We hypothesized that mutations of IGF-IR gene might predispose to short stature in children born with intrauterine growth retardation (IUGR). PATIENTS Twenty-four children with unexplained IUGR (birth weight < -1.5 SD) and short stature (<-2.0 SD) were screened for abnormalities of the IGF-IR gene. METHODS Direct DNA sequencing was used to identify IGF-IR gene mutations. Unprocessed IGF-IR proreceptor in fibroblasts was detected by immunoblot analysis. Functions of mutated IGF-IR in fibroblasts were evaluated by IGF-I binding, and IGF-I-stimulated DNA synthesis and beta-subunit autophosphorylation. RESULTS We found the following results: 1) a heterozygous mutation (R709Q) changing the cleavage site from Arg-Lys-Arg-Arg to Arg-Lys-Gln-Arg was identified in a 6-yr-old Japanese girl (case 1) and her mother who also had IUGR with short stature (case 2); 2) fibroblasts from case 2 contained more IGF-IR proreceptor protein (189 +/- 26% of normal) and less mature beta-subunit protein (63 +/- 12%); 3) [125I]IGF-I binding to fibroblasts from case 2 was reduced, compared with normal control (0.61 +/- 0.16 x 10(6) vs. 1.14 +/- 0.12 x 10(6) sites per cell; P < 0.05); and 4) both IGF-I-stimulated [3H]thymidine incorporation and IGF-IR beta-subunit autophosphorylation were low in fibroblasts from case 2, compared with those of control (P < 0.05). CONCLUSIONS These findings strongly suggest that this mutation leads to failure of processing of the IGF-IR proreceptor to mature IGF-IR and causes short stature and IUGR.
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Affiliation(s)
- Yuki Kawashima
- Division of Pediatrics and Perinatology, Tottori University, 36-1, Nishi-machi, Yonago 683-8504, Japan
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6
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Roebroek AJM, Taylor NA, Louagie E, Pauli I, Smeijers L, Snellinx A, Lauwers A, Van de Ven WJM, Hartmann D, Creemers JWM. Limited redundancy of the proprotein convertase furin in mouse liver. J Biol Chem 2004; 279:53442-50. [PMID: 15471862 DOI: 10.1074/jbc.m407152200] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Furin is an endoprotease of the family of mammalian proprotein convertases and is involved in the activation of a large variety of regulatory proteins by cleavage at basic motifs. A large number of substrates have been attributed to furin on the basis of in vitro and ex vivo data. However, no physiological substrates have been confirmed directly in a mammalian model system, and early embryonic lethality of a furin knock-out mouse model has precluded in vivo verification of most candidate substrates. Here, we report the generation and characterization of an interferon inducible Mx-Cre/loxP furin knock-out mouse model. Induction resulted in near-complete ablation of the floxed fur exon in liver. In sharp contrast with the general furin knock-out mouse model, no obvious adverse effects were observed in the transgenic mice after induction. Histological analysis of the liver did not reveal any overt deviations from normal morphology. Analysis of candidate substrates in liver revealed complete redundancy for the processing of the insulin receptor. Variable degrees of redundancy were observed for the processing of albumin, alpha(5) integrin, lipoprotein receptor-related protein, vitronectin and alpha(1)-microglobulin/bikunin. None of the tested substrates displayed a complete block of processing. The absence of a severe phenotype raises the possibility of using furin as a local therapeutic target in the treatment of pathologies like cancer and viral infections, although the observed redundancy may require combination therapy or the development of a more broad spectrum convertase inhibitor.
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MESH Headings
- Albumins/metabolism
- Alleles
- Alpha-Globulins/metabolism
- Amino Acid Motifs
- Animals
- Blotting, Northern
- Blotting, Western
- DNA Primers/chemistry
- Electrophoresis, Polyacrylamide Gel
- Furin/chemistry
- Furin/metabolism
- Furin/physiology
- Genotype
- Immunohistochemistry
- Integrin alpha5/metabolism
- Liver/metabolism
- Membrane Glycoproteins/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Models, Genetic
- Neoplasms/metabolism
- Phenotype
- Proprotein Convertases/chemistry
- Protein Structure, Tertiary
- RNA, Messenger/metabolism
- Receptors, LDL/metabolism
- Recombinant Proteins/metabolism
- Recombination, Genetic
- Reverse Transcriptase Polymerase Chain Reaction
- Substrate Specificity
- Transgenes
- Trypsin Inhibitor, Kunitz Soybean/metabolism
- Vitronectin/metabolism
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Affiliation(s)
- Anton J M Roebroek
- Experimental Mouse Genetics, University of Leuven and Flanders Interuniversity Institute for Biotechnology, B-3000 Leuven, Belgium
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7
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Qian F, Boletta A, Bhunia AK, Xu H, Liu L, Ahrabi AK, Watnick TJ, Zhou F, Germino GG. Cleavage of polycystin-1 requires the receptor for egg jelly domain and is disrupted by human autosomal-dominant polycystic kidney disease 1-associated mutations. Proc Natl Acad Sci U S A 2002; 99:16981-6. [PMID: 12482949 PMCID: PMC139255 DOI: 10.1073/pnas.252484899] [Citation(s) in RCA: 228] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Polycystin-1 plays an essential role in renal tubular morphogenesis, and disruption of its function causes cystogenesis in human autosomal-dominant polycystic kidney disease (ADPKD). We demonstrated that polycystin-1 undergoes cleavage at G protein coupled receptor proteolytic site in a process that requires the receptor for egg jelly domain. Most of the N-terminal fragment remains tethered at the cell surface, although a small amount is secreted. PKD1-associated mutations in the receptor for egg jelly domain disrupt cleavage, abolish the ability of polycystin-1 to activate signal transducer and activator of transcription-1, and induce tubulogenesis in vitro. We conclude that the cleavage of polycystin-1 is likely essential for its biologic activity.
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Affiliation(s)
- Feng Qian
- Department of Medicine, Division of Nephrology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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8
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Ko KW, McLeod RS, Avramoglu RK, Nimpf J, FitzGerald DJ, Vukmirica J, Yao Z. Mutation at the processing site of chicken low density lipoprotein receptor-related protein impairs efficient endoplasmic reticulum exit, but proteolytic cleavage is not essential for its endocytic functions. J Biol Chem 1998; 273:27779-85. [PMID: 9774386 DOI: 10.1074/jbc.273.43.27779] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The low density lipoprotein receptor-related protein (LRP) is synthesized as a proreceptor that undergoes post-translational proteolytic processing, yielding a noncovalently associated alphabeta dimer as the mature LRP. We tested the role of processing by creating a mutant in which the P1 residue (Arg3942) of the consensus site for furin cleavage (Arg-Asn-Arg-Arg3942 downward arrow) was replaced with Ser in chicken LRP. Transfection of the mutant LRP (designated LRP-RS) into a Chinese hamster ovary cell line lacking endogenous LRP resulted in expression of the unprocessed full-length proreceptor. Comparison of cell lines stably expressing either the wild-type LRP (LRP-wt) or the unprocessed LRP-RS showed that at comparable expression levels, both receptors restored the sensitivity of cellular protein synthesis to Pseudomonas exotoxin A (IC50 = 25 ng/ml). Subcellular fractionation and neuraminidase treatment showed that both LRP forms were transported to the plasma membrane. In addition, LRP-RS exhibited kinetics of binding, endocytosis, and degradation of methylamine-activated alpha2-macroglobulin that were identical to those of LRP-wt. The internalization rate constant was similar for LRP-wt (Ke = 0.259 min-1) and mutant LRP-RS (Ke = 0.252 min-1), suggesting that it takes about 4 min for the entire surface LRP pool to be internalized. Sorting of LRP from the endosomal compartment to lysosomes or recycling to the plasma membrane were also unaltered in mutant LRP-RS. Pulse-chase analysis showed that the lack of processing of LRP had no effect on the stability of its post-endoplasmic reticulum form or on the rate of its intracellular transit from the endoplasmic reticulum to the Golgi apparatus. However, the exit of mutant LRP from the endoplasmic reticulum was retarded by the Arg3942-to-Ser substitution, as evidenced by prolonged retention within the endoplasmic reticulum (t1/2 = 4 h for LRP-wt and t1/2 > 13 h for LRP-RS).
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Affiliation(s)
- K W Ko
- Lipoprotein and Atherosclerosis Group, University of Ottawa Heart Institute, Ottawa, Canada
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9
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Li S, Zhang H, Hoff H, Sell C. Activation of the insulin-like growth factor type 1 receptor by deletion of amino acids 870-905. Exp Cell Res 1998; 243:326-33. [PMID: 9743592 DOI: 10.1006/excr.1998.4167] [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: 11/22/2022]
Abstract
We have created a deletion mutant of the insulin-like growth factor type 1 receptor (IGF-1 R) which lacks the 36 amino acids (aa) immediately N-terminal to the transmembrane domain (Delta870-905 IGF-1 R). This region has been reported to have a negative effect on the transforming potential of an avian sarcoma virus gag-IGF-1 R fusion protein. We have sought to determine whether this region plays a similar role in the intact IGF-1 R. Analysis of the tyrosine kinase activity of the Delta870-905 IGF-1 R shows that the mutant receptor is autophosphorylated without IGF-1 stimulation, indicating that the tyrosine kinase domain is constitutively active. In addition, processing of the receptor is decreased, resulting in accumulation of a high molecular weight proreceptor containing both alpha and beta-subunits. A well-characterized substrate of the IGF-1 R, IRS-1, is constitutively phosphorylated by the Delta870-905 IGF-1 R and phosphoinositide (PI) 3-kinase activity, which is normally activated by the phosphorylation of IRS-1 following IGF-1 stimulation, is increased even in the absence of IGF-1. A second intracellular signal pathway normally activated by IGF-1, the MAP kinase pathway, showed no increase in activity in the absence of IGF-1. The Delta870-905 IGF-1 R promoted cell proliferation only in the presence of IGF-1. We conclude that this deletion increases the basal activity of the IGF-1 receptor tyrosine kinase and activates PI 3-kinase, but is unable to stimulate MAP kinase in the absence of ligand. These results confirm those seen in the gag-IGF-1 R fusion protein and indicate that aa 870-905 exert a negative effect on the tyrosine kinase domain of the beta-subunit of the IGF-1 R.
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Affiliation(s)
- S Li
- Department of Pathology and Laboratory Medicine, MCP-Hahnemann School of Medicine, Allegheny University, 2900 Queen Lane, Philadelphia, Pennsylvania 19129, USA
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10
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Graf R, Neuenschwander S, Brown MR, Ackermann U. Insulin-mediated secretion of ecdysteroids from mosquito ovaries and molecular cloning of the insulin receptor homologue from ovaries of bloodfed Aedes aegypti. INSECT MOLECULAR BIOLOGY 1997; 6:151-163. [PMID: 9099579 DOI: 10.1111/j.1365-2583.1997.tb00083.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The reproductive cycle of female mosquitoes is activated by ingestion of blood from vertebrate hosts. Shortly after feeding, neurohormones are released from the brain neurosecretory system and stimulate the ovaries to secrete ecdysteroids, which are necessary for vitellogenesis by the fat body. Because bombyxins, which are insulin-like peptides, stimulate ecdysteriodgenesis in silkworm larvae, we tested porcine insulin and found that it activates ecdysteroidogenesis and protein synthesis in ovaries isolated from unfed mosquitoes. To further characterize the regulation of ecdysteroidogenesis in female mosquitoes, we cloned the mosquito insulin receptor (MIR) homologue from ovarian mRNA. The sequence of the extracellular domain shows moderate homologies with vertebrate and Drosophila insulin receptor homologues, as well as with the insulin receptor-related receptor, the latter being an "orphan" receptor with an unknown function. In the intracellular domain, high homologies are observed, particularly in those subdomains that are responsible for ATP binding and kinase activity. Northern blot analysis of MIR demonstrated a highly specific expression in ovaries, and cloning experiments indicated its presence in the brain. Recombinant MIR extracts from a baculovirus expression system contained high constitutive kinase activity in the presence of manganese or magnesium. Activation was independent of a ligand. SDS-gel analysis suggested that the recombinant receptor was not post-translationally processed into an alpha- and beta-subunit as was expected from a putative cleavage signal. Enzymatic properties of the proreceptor are presented: the Km for ATP was between 15 and 50 microM in the presence of a synthetic substrate: maximal kinase activity to 100-fold over basic activity was reached in the presence of 1 mM manganese. Stimulation of key oogenic processes by porcine insulin and identification of a MIR indicate that insulin-like neurohormones may have an important regulatory role in mosquito oogenesis.
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Affiliation(s)
- R Graf
- Zoologisches Insitut, Universität Zürich, Switzerland
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11
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Affiliation(s)
- D Accili
- Diabetes Branch, NIDDK, Bethesda, MD 20892, USA
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12
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Pulido R, Krueger NX, Serra-Pagès C, Saito H, Streuli M. Molecular characterization of the human transmembrane protein-tyrosine phosphatase delta. Evidence for tissue-specific expression of alternative human transmembrane protein-tyrosine phosphatase delta isoforms. J Biol Chem 1995; 270:6722-8. [PMID: 7896816 DOI: 10.1074/jbc.270.12.6722] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Protein-tyrosine phosphatases (PTPases) play an essential role in the regulation of cell activation, proliferation, and differentiation. A major subfamily of these enzymes is the transmembrane-type PTPases that contain extracellular regions comprised of Ig-like and fibronectin type III (FN-III)-like domains. Characterization of the human transmembrane PTPase delta (HPTP delta) revealed the existence of multiple HPTP delta isoforms that vary in their extracellular regions. The full-length HPTP delta isoform has an extracellular region containing three Ig-like and eight FN-III-like domains connected via a transmembrane peptide to an intracellular region with two PTPase domains, whereas another isoform lacks four of the eight FN-III like domains. Furthermore, other HPTP delta isoforms exist that lack 9 amino acids within the second Ig-like domain and 4 amino acids at the junction of the second and third Ig-like domains or 9 amino acids within the fifth FN-III-like domain. Reverse transcription polymerase chain reaction analysis demonstrated that HPTP delta isoforms lacking these short peptides are expressed in kidney, whereas isoforms containing these peptides are expressed in the brain. Analysis of HPTP delta biosynthesis demonstrated that HPTP delta is expressed as a complex of two noncovalently associated subunits derived from a proprotein and that the HPTP delta ectodomain is shed from the cell surface. Mutational analysis of the HPTP delta proprotein cleavage site revealed the existence of two or three functional and overlapping furin-like endoprotease cleavage sites.
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Affiliation(s)
- R Pulido
- Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115
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13
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Pashmforoush M, Yoshimasa Y, Steiner DF. Exon 11 enhances insulin binding affinity and tyrosine kinase activity of the human insulin proreceptor. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)31682-x] [Citation(s) in RCA: 8] [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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14
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Serra-Pages C, Saito H, Streuli M. Mutational analysis of proprotein processing, subunit association, and shedding of the LAR transmembrane protein tyrosine phosphatase. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31562-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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15
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van der Vorm E, Kuipers A, Kielkopf-Renner S, Krans H, Möller W, Maassen J. A mutation in the insulin receptor that impairs proreceptor processing but not insulin binding. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36788-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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16
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Rolband GC, Williams JF, Webster NJ, Hsu D, Olefsky JM. Deletion of exon 21 of the insulin receptor eliminates tyrosine kinase activity but preserves mitogenic signaling. Biochemistry 1993; 32:13545-50. [PMID: 8257690 DOI: 10.1021/bi00212a021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
To study the function of exon 21 of the insulin receptor, a mutant human insulin receptor lacking this domain was constructed. The mutant HIR delta E21 cDNA was transfected into Rat-1 fibroblasts and stable cell lines were selected. The HIR delta E21 receptors were expressed on the cell surface, and they bound insulin with the same affinity as did the wild-type-expressing cell line, hIRcB. The HIR delta E21 receptors did not display detectable autophosphorylation or kinase activity, and as expected, internalization was impaired and metabolic signaling properties were absent. Unexpectedly, insulin's ability to stimulate DNA synthesis in cells expressing HIR delta E21 receptors was far greater than that in the parental Rat-1 cells and equal to that measured in the hIRcB cell line. The enhanced mitogenic signaling properties of the HIR delta E21 receptors was confirmed by showing that treatment of HIR delta E21 cells with a human-specific insulin-mimetic anti-insulin receptor antibody also led to enhanced DNA synthesis. Thus, although no insulin receptor autophosphorylation or kinase activity was detectable in HIR delta E21 cells, these cells displayed enhanced insulin-induced mitogenic signaling. These results suggest that an alternative non-kinase-dependent stimulus-response pathway exists for the long-term biological effects of insulin.
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Affiliation(s)
- G C Rolband
- Department of Medicine, University of California at San Diego, La Jolla 92093
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17
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Tavaré JM, Siddle K. Mutational analysis of insulin receptor function: consensus and controversy. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1178:21-39. [PMID: 8329456 DOI: 10.1016/0167-4889(93)90106-y] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- J M Tavaré
- Department of Biochemistry, School of Medical Sciences, University of Bristol, UK
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18
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Kahn CR, White MF, Shoelson SE, Backer JM, Araki E, Cheatham B, Csermely P, Folli F, Goldstein BJ, Huertas P. The insulin receptor and its substrate: molecular determinants of early events in insulin action. RECENT PROGRESS IN HORMONE RESEARCH 1993; 48:291-339. [PMID: 7680139 DOI: 10.1016/b978-0-12-571148-7.50015-4] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- C R Kahn
- Joslin Diabetes Center, Department of Medicine Brigham and Women's Hospital, Boston, Massachusetts
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19
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Sugibayashi M, Shigeta Y, Teraoka H, Kobayashi M. Characterization of unprocessed insulin proreceptors in COS 7 cells transfected with cDNA with Arg735----Ser735 point mutation at the cleavage site. Metabolism 1992; 41:820-6. [PMID: 1640858 DOI: 10.1016/0026-0495(92)90161-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We previously reported on patients with severe insulin resistance due to unprocessed insulin proreceptors. A structural change of the cleavage site from Arg-Lys-Arg-Arg to Arg-Lys-Arg-Ser due to G----T point mutation appeared to be the cause for failure to process the proreceptors. To determine whether the mutation of insulin proreceptors at the cleavage site was responsible for unprocessed insulin receptors and to elucidate the structural and binding characteristics of the proreceptors, we transfected cDNA with the mutation in COS 7 cells and examined the expressed insulin receptors. At 72 hours after transfection, insulin binding increased to the maximum in cells transfected with either normal or mutated cDNA, and insulin binding was 40 and 14 times higher than that of nontransfected cells, respectively. The declining rate of insulin binding after reaching the maximum was delayed in cells transfected with mutated cDNA. Affinity cross-linking and surface-labeling studies showed a 135-kilodalton (kD), normal alpha-subunit in the cells transfected with normal cDNA and a 210-kD proreceptor in the mutant cells. The proreceptors were cleaved by trypsin to yield normal-sized alpha- and beta-subunits. The sensitivity to trypsin was similar to that demonstrated in patients' cells, and the most effective concentration for the cleavage was 0.025%. Autophosphorylation resulted in decreased 32P incorporation into proreceptors of cells transfected with mutated cDNA at both basal and insulin-stimulated states, without a change in insulin sensitivity. Competitive binding studies with insulin, proinsulin, and miniproinsulin showed that the proreceptors had a lower relative affinity for proinsulin, but this characteristic disappeared after trypsin treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Sugibayashi
- Third Department of Medicine, Shiga University of Medical Science, Japan
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Siddle K. The insulin receptor and type I IGF receptor: comparison of structure and function. PROGRESS IN GROWTH FACTOR RESEARCH 1992; 4:301-20. [PMID: 1340212 DOI: 10.1016/0955-2235(92)90013-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The insulin receptor and type I IGF receptor are closely related in structure and function. The receptors are heterotetrameric glycoproteins, of structure alpha beta beta alpha, which are widely distributed in mammalian tissues. A third member of this receptor family has been described, the insulin receptor-related receptor for which a ligand has still to be identified. It has also been demonstrated that the insulin receptor and IGF receptor form alpha beta beta alpha hybrids in cells expressing both receptors. The key elements in the function of any receptor are recognition of ligand and transmission of an intracellular signal. In the insulin and IGF receptors, determinants of binding specificity are contained within amino-terminal and cysteine-rich domains of the extracellular alpha-subunit. Intracellular signalling is dependent on ligand activated tyrosine kinase activity in the transmembrane beta-subunit, which phosphorylates both the receptor itself and the specific substrate insulin receptor substrate-1 (IRS-1). Phosphorylated IRS-1 binds the enzyme phosphatidylinositol 3-kinase and may act as a multivalent docking site for SH2 domains of other proteins involved in signalling. The possibility that some signalling molecules interact directly with the receptors has not been ruled out. The specificity of action of insulin and IGFs in vivo depends on differences between the respective receptors in tissue distribution, ligand binding specificity and intrinsic signalling capacity. However, the detailed aspects of gene and receptor structure which underly these functional differences are still poorly understood. Moreover, the issue of specificity is complicated by the existence of hybrid and atypical receptors, which in principle could bind and respond to both insulin and IGF-I, although the physiological significance of these receptor subtypes is at present unclear.
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Affiliation(s)
- K Siddle
- Department of Clinical Biochemistry, University of Cambridge Addenbrooke's Hospital, U.K
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An Arg for Gly substitution at position 31 in the insulin receptor, linked to insulin resistance, inhibits receptor processing and transport. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)48459-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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