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Ahmed M, Biswas T, Mondal S. The strategic involvement of IRS in cancer progression. Biochem Biophys Res Commun 2023; 680:141-160. [PMID: 37738904 DOI: 10.1016/j.bbrc.2023.09.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 09/13/2023] [Accepted: 09/15/2023] [Indexed: 09/24/2023]
Abstract
Insulin Receptor Substrate (IRS), an intracellular molecule devoid of an intrinsic kinase activity, is activated upon binding to IR which thereby works as a scaffold, organizing all signaling complexes and initiating the signaling process downstream. The level of IRS proteins and their stability in the cell is mostly maintained through the phosphorylation status of their tyrosine and serine residues. IRS is positively regulated by phosphorylation of its Tyr residues whereas a Ser residue phosphorylation attenuates it, although there exist some exceptions as well. Other post-translational modifications like O-linked glycosylation, N-linked glycosylation and acetylation also play a prominent role in IRS regulation. Since the discovery of the Warburg effect, people have been curious to find out all possible signaling networks and molecules that could lead to cancer and no doubt, the insulin signaling pathway is identified as one such pathway, which is highly deregulated in cancers. Eminent studies reveal that IRS is a pertinent regulator of cancer and is highly overexpressed in the five most commonly occurring cancers namely- Prostate, Ovarian, Breast, Colon and Lung cancers. IRS1 and IRS2 family members are actively involved in the progression, invasion and metastasis of these cancers. Recently, less studied IRS4 has also emerged as a contributor in ovarian, breast, colorectal and lung cancer, but no such studies related to IRS4 are found in Prostate cancer. The involvement of other IRS family members in cancer is still undiscovered and so paves the way for further exploration. This review is a time-lapse study of IRSs in the context of cancer done over the past two decades and it highlights all the major discoveries made till date, in these cancers from the perspective of IRS.
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Affiliation(s)
- Mehnaz Ahmed
- Department of Life Sciences, Presidency University, 86/1 College Street, Kolkata, 700073, West Bengal, India
| | - Tannishtha Biswas
- Department of Life Sciences, Presidency University, 86/1 College Street, Kolkata, 700073, West Bengal, India
| | - Susmita Mondal
- Department of Life Sciences, Presidency University, 86/1 College Street, Kolkata, 700073, West Bengal, India.
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Janse van Rensburg HJ, Lai D, Azad T, Hao Y, Yang X. TAZ enhances mammary cell proliferation in 3D culture through transcriptional regulation of IRS1. Cell Signal 2018; 52:12-22. [PMID: 30138697 DOI: 10.1016/j.cellsig.2018.08.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 08/16/2018] [Accepted: 08/17/2018] [Indexed: 12/13/2022]
Abstract
WW domain-containing transcriptional regulator 1 (TAZ) is a transcriptional co-activator and effector of the Hippo signaling pathway. In certain breast cancer subtypes, Hippo signaling is dysregulated leading to activation of TAZ and altered expression of TAZ transcriptional targets. Over the past decade, we and others have found that TAZ transcriptionally regulates genes that affect multiple aspects of breast cancer cell behaviour. However, while cancer cell-intrinsic oncogenic functions of TAZ have emerged, less is known about whether TAZ might also contribute to tumourigenesis by sensitizing tumour cells to factors present in the tumour microenvironment or in systemic circulation. Here, we show that TAZ directly regulates the expression of insulin receptor substrate 1 (IRS1) in breast cancer cells. TAZ or IRS1 overexpression induces a similar proliferative transformation phenotype in MCF10A mammary epithelial cells. TAZ enhances IRS1 mRNA, protein levels and downstream signaling in MCF10A. Mechanistically, TAZ interacts with the IRS1 promoter through the TEAD family of transcription factors and enhances its activity. Critically, TAZ-induced IRS1 upregulation contributes to the proliferation of TAZ-overexpressing MCF10A in 3-dimensional (3D) Matrigel culture. Therefore, we offer compelling evidence that TAZ regulates signaling through the insulin pathway in breast cancer cells. These findings highlight an additional mechanism by which TAZ may promote breast cancer tumourigenesis and progression by modulating cancer cell responses to exogenously produced factors.
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Affiliation(s)
| | - Dulcie Lai
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Taha Azad
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Yawei Hao
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Xiaolong Yang
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario K7L 3N6, Canada.
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Purushothaman A, Babitz SK, Sanderson RD. Heparanase enhances the insulin receptor signaling pathway to activate extracellular signal-regulated kinase in multiple myeloma. J Biol Chem 2012; 287:41288-96. [PMID: 23048032 DOI: 10.1074/jbc.m112.391417] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
ERK signaling regulates proliferation, survival, drug resistance, and angiogenesis in cancer. Although the mechanisms regulating ERK activation are not fully understood, we previously demonstrated that ERK phosphorylation is elevated by heparanase, an enzyme associated with aggressive behavior of many cancers. In the present study, myeloma cell lines expressing either high or low levels of heparanase were utilized to determine how heparanase stimulates ERK signaling. We discovered that the insulin receptor was abundant on cells expressing either high or low levels of heparanase, but the receptor was highly phosphorylated in heparanase-high cells compared with heparanase-low cells. In addition, protein kinase C activity was elevated in heparanase-high cells, and this enhanced expression of insulin receptor substrate-1 (IRS-1), the principle intracellular substrate for phosphorylation by the insulin receptor. Blocking insulin receptor function with antibody or a small molecule inhibitor or knockdown of IRS-1 expression using shRNA diminished heparanase-mediated ERK activation in the tumor cells. In addition, up-regulation of the insulin signaling pathway by heparanase and the resulting ERK activation were dependent on heparanase retaining its enzyme activity. These results reveal a novel mechanism whereby heparanase enhances activation of the insulin receptor signaling pathway leading to ERK activation and modulation of myeloma behavior.
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Affiliation(s)
- Anurag Purushothaman
- Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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Shi J, Wang DM, Wang CM, Hu Y, Liu AH, Zhang YL, Sun B, Song JG. Insulin Receptor Substrate-1 Suppresses Transforming Growth Factor-β1–Mediated Epithelial-Mesenchymal Transition. Cancer Res 2009; 69:7180-7. [DOI: 10.1158/0008-5472.can-08-4470] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Cortés V, Amigo L, Donoso K, Valencia I, Quiñones V, Zanlungo S, Brandan E, Rigotti A. Adenovirus-mediated hepatic syndecan-1 overexpression induces hepatocyte proliferation and hyperlipidaemia in mice. Liver Int 2007; 27:569-81. [PMID: 17403197 DOI: 10.1111/j.1478-3231.2007.01442.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
BACKGROUND Heparan sulfate proteoglycans (HSPGs) have been involved in the regulation of cell growth, apoptosis and lipid metabolism in vitro; however, their functional role in vivo remains unknown. AIM Here, we describe hepatic tissue and lipid metabolism changes after liver overexpression of syndecan-1 (SDC-1), the main hepatic HSPG, in mice induced by adenoviral gene transfer. RESULTS SDC-1 overexpression was associated with marked hepatocyte proliferation, cell-isolated apoptosis and increased plasma alanine aminotransferase (ALT) levels. Additionally, SDC-1 liver overexpression significantly raised plasma cholesterol and triglyceride concentrations due to an increase in all lipoprotein particles, including the appearance of large and apolipoprotein (apo) E-enriched high-density lipoprotein (HDL) particles. Hepatic very low-density lipoprotein (VLDL) production was not affected by SDC-1 overexpression, suggesting a delayed plasma clearance of apo B lipoproteins as the underlying hyperlipidaemic mechanism. These pleotropic effects were qualitatively equivalent, even though less intense, in mice overexpressing a cytoplasmic C-terminal domain-deleted SDC-1. CONCLUSIONS This is the first report in vivo of the biological effects induced by a specific HSPG in the liver, with potential implications in both regenerative biology and molecular lipidology.
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Affiliation(s)
- Víctor Cortés
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica de Chile
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Cesarone G, Garofalo C, Abrams MT, Igoucheva O, Alexeev V, Yoon K, Surmacz E, Wickstrom E. RNAi-mediated silencing of insulin receptor substrate 1 (IRS-1) enhances tamoxifen-induced cell death in MCF-7 breast cancer cells. J Cell Biochem 2006; 98:440-50. [PMID: 16440325 DOI: 10.1002/jcb.20817] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Insulin receptor substrate 1 (IRS-1) is a major downstream signaling protein for insulin and insulin-like growth factor I (IGF-I) receptors, conveying signals to PI-3K/Akt and ERK1/2 pathways. In breast cancer, IRS-1 overexpression has been associated with tumor development, hormone-independence and antiestrogen-resistance. In part, these effects are related to potentiation of IRS-1/PI-3K/Akt signaling. In estrogen sensitive breast cancer cell lines, tamoxifen treatment reduces IRS-1 expression and function; consequently, inhibiting IRS-1/PI-3K signaling. We tested whether anti-IRS1 siRNA could inhibit growth and survival of estrogen-sensitive MCF-7 breast cancer cells, when used alone or in combination with TAM. Our results indicated: (a) out of four tested anti-IRS1 siRNAs, two siRNAs reduced IRS-1 protein by approximately three-fold in both growing and IGF-I-stimulated cells without affecting a closely related protein, IRS-2; (b) these effects paralleled IRS1 mRNA downregulation by approximately three-fold, measured by quantitative real time-polymerase chain reaction; (c) action of anti-IRS1 siRNAs induced the apoptotic response, observed by altered mitochondrial membrane potential coupled with downregulation of NF-kappaB target Bcl-xL and reduced cell viability; (d) anti-IRS1 siRNA treatment enhanced the cytotoxic effects of TAM by approximately 20%. In summary, anti-IRS1 RNAi strategy could become a potent tool to induce breast cancer cell death, especially if combined with standard TAM therapy.
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Affiliation(s)
- Gregory Cesarone
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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Chakravarti R, Adams JC. Comparative genomics of the syndecans defines an ancestral genomic context associated with matrilins in vertebrates. BMC Genomics 2006; 7:83. [PMID: 16620374 PMCID: PMC1464127 DOI: 10.1186/1471-2164-7-83] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Accepted: 04/18/2006] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND The syndecans are the major family of transmembrane proteoglycans in animals and are known for multiple roles in cell interactions and growth factor signalling during development, inflammatory response, wound-repair and tumorigenesis. Although syndecans have been cloned from several invertebrate and vertebrate species, the extent of conservation of the family across the animal kingdom is unknown and there are gaps in our knowledge of chordate syndecans. Here, we develop a new level of knowledge for the whole syndecan family, by combining molecular phylogeny of syndecan protein sequences with analysis of the genomic contexts of syndecan genes in multiple vertebrate organisms. RESULTS We identified syndecan-encoding sequences in representative Cnidaria and throughout the Bilateria. The C1 and C2 regions of the cytoplasmic domain are highly conserved throughout the animal kingdom. We identified in the variable region a universally-conserved leucine residue and a tyrosine residue that is conserved throughout the Bilateria. Of all the genomes examined, only tetrapod and fish genomes encode multiple syndecans. No syndecan-1 was identified in fish. The genomic context of each vertebrate syndecan gene is syntenic between human, mouse and chicken, and this conservation clearly extends to syndecan-2 and -3 in T. nigroviridis. In addition, tetrapod syndecans were found to be encoded from paralogous chromosomal regions that also contain the four members of the matrilin family. Whereas the matrilin-3 and syndecan-1 genes are adjacent in tetrapods, this chromosomal region appears to have undergone extensive lineage-specific rearrangements in fish. CONCLUSION Throughout the animal kingdom, syndecan extracellular domains have undergone rapid change and elements of the cytoplasmic domains have been very conserved. The four syndecan genes of vertebrates are syntenic across tetrapods, and synteny of the syndecan-2 and -3 genes is apparent between tetrapods and fish. In vertebrates, each of the four family members are encoded from paralogous genomic regions in which members of the matrilin family are also syntenic between tetrapods and fish. This genomic organization appears to have been set up after the divergence of urochordates (Ciona) and vertebrates. The syndecan-1 gene appears to have been lost relatively early in the fish lineage. These conclusions provide the basis for a new model of syndecan evolution in vertebrates and a new perspective for analyzing the roles of syndecans in cells and whole organisms.
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Affiliation(s)
- Ritu Chakravarti
- Dept. of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, USA
| | - Josephine C Adams
- Dept. of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, USA
- Dept. of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland Clinic Foundation, Cleveland, OH 44195, USA
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Allain F, Vanpouille C, Denys A, Pakula R, Carpentier M, Mazurier J. Involvement of GAGs in the activity of pro-inflammatory factors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2004; 535:95-106. [PMID: 14714891 DOI: 10.1007/978-1-4615-0065-0_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Affiliation(s)
- Fabrice Allain
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR no 8576 du CNRS, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France
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Susarla BTS, Robinson MB. Rottlerin, an inhibitor of protein kinase Cdelta (PKCdelta), inhibits astrocytic glutamate transport activity and reduces GLAST immunoreactivity by a mechanism that appears to be PKCdelta-independent. J Neurochem 2003; 86:635-45. [PMID: 12859677 DOI: 10.1046/j.1471-4159.2003.01886.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Protein kinase C (PKC) regulates the activity and/or cell surface expression of several different neurotransmitter transporters, including subtypes of glutamate transporters. In the present study, the effects of pharmacological inhibitors of PKC were studied in primary astrocyte cultures that express the glutamate aspartate transporter (GLAST) subtype of glutamate transporter. We found that general inhibitors of PKC, bisindolylmaleimide I (Bis I), bisindolylmaleimide II (Bis II), staurosporine and an inhibitor of classical PKCs, Gö6976, had no effect on Na+-dependent glutamate transport activity. However, rottlerin, a putative specific inhibitor of PKCdelta, decreased transport activity with an IC50 value (less than 10 micro m) that is comparable to that reported for inhibition of PKCdelta. The effect of rottlerin was very rapid (maximal effect within 5 min) and was due to a decrease in the capacity (Vmax) for transport. Rottlerin also caused a drastic loss of GLAST immunoreactivity within 5 min, suggesting that rottlerin accelerates GLAST degradation/proteolysis. Rottlerin had no effect on cell surface or total expression of the transferrin receptor, providing evidence that the effect on GLAST cannot be attributed to a non-specific internalization/degradation of plasma membrane proteins. Down-regulation of PKCdelta with chronic phorbol ester treatment did not block rottlerin-mediated inhibition of transport activity. These results suggest a novel mechanism for regulation of the GLAST subtype of glutamate transporter and indicate that there is a rottlerin target that is capable of controlling the levels of GLAST by controlling the rate of degradation or limited proteolysis. It appears that the target for rottlerin may not be PKCdelta.
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Affiliation(s)
- Bala T S Susarla
- Departments of Pediatrics and Pharmacology, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, Pennsylvania 19104-4318, USA
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del Rincón SV, Rousseau C, Samanta R, Miller WH. Retinoic acid-induced growth arrest of MCF-7 cells involves the selective regulation of the IRS-1/PI 3-kinase/AKT pathway. Oncogene 2003; 22:3353-60. [PMID: 12776186 DOI: 10.1038/sj.onc.1206485] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In the MCF-7 breast cancer cell line, insulin-like growth factors (IGFs) are known to elicit antiproliferative actions via the insulin receptor substrate-1 (IRS-1)/PI 3-kinase/AKT pathway. All-trans retinoic acid (RA) is a potent inhibitor of MCF-7 cell proliferation, but the mechanism by which growth regulation is achieved remains unclear. We investigated the effects of RA on the regulation of the IGF-IR and its key signaling elements: IRS-1, IRS-2, and SHC. Treatment of MCF-7 cells with RA caused a significant reduction in IRS-1 protein and tyrosine phosphorylation levels at a concentration and time consistent with RA-mediated growth inhibition. IRS-1 regulation is selective, as RA did not influence IRS-2 or SHC levels. Downstream signaling events were also selectively reduced, as RA abrogated IGF-I-stimulated AKT activation but did not alter erk1/2 activation. To confirm the importance of IRS-1 regulation by RA, we examined the response to RA in MCF-7 cells overexpressing IGF-IR and IRS-1. RA resistance was observed in MCF-7 cells overexpressing IRS-1 but not IGF-IR. This suggests that RA-mediated growth inhibition requires the selective downregulation of IRS-1 and AKT. Therapeutic agents targeting the IRS-1/PI 3-kinase/AKT pathway may enhance the cytostatic effects of RA in breast cancer, since overexpression of IRS-1 and AKT have been reported in primary breast tumors.
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Affiliation(s)
- Sonia V del Rincón
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital and McGill University, Department of Oncology, Montreal, Quebec, Canada
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Affiliation(s)
- E Shafrir
- Department of Medicine, Diabetes Research Centre, Hadassah University Hospital, Ein Kerem, Jerusalem, 91120 Israel.
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Che W, Lerner-Marmarosh N, Huang Q, Osawa M, Ohta S, Yoshizumi M, Glassman M, Lee JD, Yan C, Berk BC, Abe JI. Insulin-like growth factor-1 enhances inflammatory responses in endothelial cells: role of Gab1 and MEKK3 in TNF-alpha-induced c-Jun and NF-kappaB activation and adhesion molecule expression. Circ Res 2002; 90:1222-30. [PMID: 12065326 DOI: 10.1161/01.res.0000021127.83364.7d] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Insulin-like growth factor (IGF)-1 and the type I IGF-1 receptor are important regulators of vascular function that may contribute to cardiovascular disease. We hypothesized that IGF-1 causes endothelial cell dysfunction and expression of neutrophil and monocyte adhesion molecules by enhancing pro-inflammatory cytokine signal transduction. Long-term IGF-1 treatment of endothelial cells potentiated c-Jun and nuclear factor NF-kappaB activation by tumor necrosis factor (TNF)-alpha and enhanced TNF-alpha-mediated adhesion molecule expression. In response to IGF-1 treatment, the expression of kinases in the c-Jun/c-Jun NH(2)-terminal kinase signaling pathway (MEKK1, MEK4, and JNK1/2) was unchanged, but expressions of insulin receptor substrate-1 and Grb2-associated binder-1 (Gab1) were significantly decreased. Because Gab1 is involved in both c-Jun and NF-kappaB activation by TNF-alpha, we focused on Gab1-dependent signaling. Gab1 inhibited c-Jun and NF-kappaB transcriptional activation by TNF-alpha. Interestingly, Gab1 inhibited c-Jun transcriptional activity induced by MEKK3 but not MEKK1 and MEK4. Gab1 associated with MEKK3, and a catalytically inactive form of MEKK3 inhibited TNF-alpha-induced c-Jun and NF-kappaB transcriptional activation, suggesting a critical role for Gab1 and MEKK3 in TNF-alpha signaling. These data demonstrate that Gab1 and MEKK3 play important roles in endothelial cell inflammation via regulating the activation of c-Jun and NF-kappaB. Furthermore, the IGF-1-mediated downregulation of Gab1 expression represents a novel mechanism to promote vascular inflammation and atherosclerosis.
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Affiliation(s)
- Wenyi Che
- Center for Cardiovascular Research, University of Rochester, Rochester, NY, USA
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Plesneva SA, Shpakov AO, Kuznetsova LA, Pertseva MN. A dual role of protein kinase C in insulin signal transduction via adenylyl cyclase signaling system in muscle tissues of vertebrates and invertebrates. Biochem Pharmacol 2001; 61:1277-91. [PMID: 11322932 DOI: 10.1016/s0006-2952(01)00592-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Further decoding of a novel adenylyl cyclase signaling mechanism (ACSM) of the action of insulin and related peptides detected earlier (Pertseva et al. Comp Biochem Physiol B Biochem Mol Biol 1995;112:689-95 and Pertseva et al. Biochem Pharmacol 1996;52:1867-74) was carried out with special attention given to the role of protein kinase C (PKC) in the ACSM. It was shown for the first time that transduction of the insulin signal via the ACSM followed by adenylyl cyclase (AC, EC 4.6.1.1) activation was blocked in the muscle tissues of rat and mollusc Anodonta cygnea in the presence of pertussis toxin, inducing the impairment of G(i)-protein function, wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3-K), and calphostin C, a blocker of PKC. The cholera toxin treatment of muscle membranes led to an increase in basal AC activity and a decrease in enzyme insulin reactivity. Phorbol ester and diacylglycerol activation of PKC (acute treatment) induced the inhibition of the insulin AC activating effect. This negative influence was also observed in the case of the AC system activated by biogenic amines. It was first concluded that the ACSM of insulin action involves the following signaling chain: receptor tyrosine kinase => G(i) (betagamma) => PI3-K => PKCzeta (?) => G(s) => AC => adenosine 3',5'-cyclic monophosphate. It was also concluded that the PKC system has a dual role in the ACSM: (1) a regulatory role (PKC sensitive to phorbol esters) that is manifested as a negative feedback modulation of insulin signal transduction via the ACSM; (2) a transductory role, which consists in direct participation of atypical PKC (PKCzeta) in the process of insulin signal transduction via the ACSM.
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Affiliation(s)
- S A Plesneva
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Thorez au. 44, 194223, St. Petersburg, Russia
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Schmitz-Peiffer C. Signalling aspects of insulin resistance in skeletal muscle: mechanisms induced by lipid oversupply. Cell Signal 2000; 12:583-94. [PMID: 11080610 DOI: 10.1016/s0898-6568(00)00110-8] [Citation(s) in RCA: 194] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A reduced capacity for insulin to elicit increases in glucose uptake and metabolism in target tissues such as skeletal muscle is a common feature of obesity and diabetes. The association between lipid oversupply and such insulin resistance is well established, and evidence for mechanisms through which lipids could play a causative role in the generation of muscle insulin resistance is reviewed. While the effects of lipids may in part be mediated by substrate competition through the glucose-fatty acid cycle, interference with insulin signal transduction by lipid-activated signalling pathways is also likely to play an important role. Thus, studies of insulin resistance in Type 2 diabetes, obesity, fat-fed animals and lipid-treated cells have identified defects both at the level of insulin receptor-mediated tyrosine phosphorylation and at downstream sites such as protein kinase B (PKB) activation. Lipid signalling molecules can be derived from free fatty acids, and include diacylglycerol, which activates isozymes of the protein kinase C (PKC) family, and ceramide, which has several effectors including PKCs and a protein phosphatase. In addition, elevated lipid availability can increase flux through the hexosamine biosynthesis pathway which can also lead to activation of PKC as well as protein glycosylation and modulation of gene expression. The mechanisms giving rise to decreased insulin signalling include serine/threonine phosphorylation of insulin receptor substrate-1, but also direct inhibition of components such as PKB. Thus lipids can inhibit glucose disposal by causing interference with insulin signal transduction, and most likely by more than one pathway depending on the prevalent species of fatty acids.
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Affiliation(s)
- C Schmitz-Peiffer
- Garvan Institute of Medical Research, 384 Victoria Street, NSW 2010, Darlinghurst, Australia.
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Bernfield M, Götte M, Park PW, Reizes O, Fitzgerald ML, Lincecum J, Zako M. Functions of cell surface heparan sulfate proteoglycans. Annu Rev Biochem 2000; 68:729-77. [PMID: 10872465 DOI: 10.1146/annurev.biochem.68.1.729] [Citation(s) in RCA: 2095] [Impact Index Per Article: 87.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The heparan sulfate on the surface of all adherent cells modulates the actions of a large number of extracellular ligands. Members of both cell surface heparan sulfate proteoglycan families, the transmembrane syndecans and the glycosylphosphoinositide-linked glypicans, bind these ligands and enhance formation of their receptor-signaling complexes. These heparan sulfate proteoglycans also immobilize and regulate the turnover of ligands that act at the cell surface. The extracellular domains of these proteoglycans can be shed from the cell surface, generating soluble heparan sulfate proteoglycans that can inhibit interactions at the cell surface. Recent analyses of genetic defects in Drosophila melanogaster, mice, and humans confirm most of these activities in vivo and identify additional processes that involve cell surface heparan sulfate proteoglycans. This chapter focuses on the mechanisms underlying these activities and on the cellular functions that they regulate.
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Affiliation(s)
- M Bernfield
- Division of Developmental and Newborn Biology, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
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Nakajima K, Yamauchi K, Shigematsu S, Ikeo S, Komatsu M, Aizawa T, Hashizume K. Selective attenuation of metabolic branch of insulin receptor down-signaling by high glucose in a hepatoma cell line, HepG2 cells. J Biol Chem 2000; 275:20880-6. [PMID: 10764799 DOI: 10.1074/jbc.m905410199] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The effects of a high concentration of glucose on the insulin receptor-down signaling were investigated in human hepatoma (HepG2) cells in vitro to delineate the molecular mechanism of insulin resistance under glucose toxicity. Treatment of the cells with high concentrations of glucose (15-33 mm) caused phosphorylation of serine residues of the insulin receptor substrate 1 (IRS-1), leading to reduced electrophoretic mobility of it. The phosphorylation of IRS-1 with high glucose treatment was blocked only by protein kinase C (PKC) inhibitors. The high glucose treatment attenuated insulin-induced association of IRS-1 and phosphatidylinositol 3-kinase and insulin-stimulated phosphorylation of Akt. A metabolic effect of insulin, stimulation of glycogen synthesis, was also inhibited by the treatment. In contrast, insulin-induced association of Shc and Grb2 was not inhibited. Treatment of the cells with high glucose promoted the translocation of PKCepsilon and PKCdelta from the cytosol to the plasma membrane but not that of other PKC isoforms. Finally, PKCepsilon and PKCdelta directly phosphorylated IRS-1 under cell-free conditions. We conclude that a high concentration of glucose causes phosphorylation of IRS-1, leading to selective attenuation of metabolic signaling of insulin. PKCepsilon and PKCdelta are involved in the down-regulation of insulin signaling, and they may lie in a pathway regulating the phosphorylation of IRS-1.
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Affiliation(s)
- K Nakajima
- Department of Aging Medicine and Geriatrics, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan
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Shanmugam M, Krett NL, Maizels ET, Cutler RE, Peters CA, Smith LM, O'Brien ML, Park-Sarge OK, Rosen ST, Hunzicker-Dunn M. Regulation of protein kinase C delta by estrogen in the MCF-7 human breast cancer cell line. Mol Cell Endocrinol 1999; 148:109-18. [PMID: 10221776 DOI: 10.1016/s0303-7207(98)00229-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We have previously shown that estrogen up-regulates expression of protein kinase C (PKC) delta in the rat and rabbit corpus luteum as well as in luteinized rat granulosa primary cell cultures. To determine whether a similar regulation of the PKC delta isoform by estrogen occurred in another estrogen responsive system, we investigated the estrogen receptor positive MCF-7 human breast cancer cells. In a characterization of PKC isoforms in MCF-7 cells we determined that PKC delta was the predominant PKC isoform. However in contrast to the effect of estrogen on PKC delta expression in ovarian cells, estrogen treatment of MCF-7 cells resulted in a significant decrease in PKC delta protein and mRNA expression in a time and dose dependent manner. Treatment of MCF-7 cells with 10(-10)-10(-8) M estrogen for 7 days down-regulated specifically PKC delta mRNA and protein while expression of other PKC isoforms was unchanged. The opposite regulation of PKC delta expression in ovarian and breast cancer cells prompted us to evaluate the type of estrogen receptor present in both cell types. Results showed that luteinized rat granulosa cells expressed predominantly estrogen receptor beta while the MCF-7 cells expressed predominantly estrogen receptor alpha and barely detectable levels of estrogen receptor beta. These results suggest that the differential ability of estrogen to regulate PKC beta expression could potentially be a result of differential signaling through the two estrogen receptor subtypes.
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Affiliation(s)
- M Shanmugam
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, IL 60611, USA
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Abstract
Epidemiological reports are inconsistent on the association between breast cancer risk and the dietary intake of either individual fatty acids or of antioxidant vitamins. It is postulated here that the inconsistencies are in part due to interactions between the two classes of nutrients at the level of the cell membrane, affecting their potential role in mammary carcinogenesis. In this review, the effects of specific dietary fatty acids and antioxidant vitamins on experimental mammary cancer systems are compared with reported epidemiological associations of the same agents with breast cancer risk in humans. An increased ratio of n-3 to n-6 polyunsaturated fatty acids (PUFAs) in the diet inhibits the growth of the rat mammary cancer model. There is also evidence that members of the n-3 PUFA series can inhibit the growth of human breast cancer cells both in vitro and in explants. Clinical trials of supplementary n-3 PUFAs in conjunction with a reduced fat intake have been proposed for breast cancer prevention. It is postulated that further dietary supplementation with vitamin E and a retinoid is likely to increase the effectiveness of such a diet. A study of this type allows better control of specific dietary components than prospective trials of dietary fat reduction which are presently under evaluation. In particular, it is suggested that studies focusing on a single nutrient often fail to recognise interactions with other nutrients.
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Affiliation(s)
- B A Stoll
- Oncology Department, St. Thomas' Hospital, London, U.K
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