Insulin-stimulated Tyrosine Phosphorylation of Caveolin Is Specific for the Differentiated Adipocyte Phenotype in 3T3-L1 Cells

Mastick, Cynthia Corley; Saltiel, Alan R.

doi:10.1074/jbc.272.33.20706

Cited by 140 publications

(129 citation statements)

References 55 publications

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“…Interestingly, insulin treatment leads to complete dissociation of Sirm from FYN. The binding of Sirm to FYN is intriguing, in view of the fact that FYN has been implicated in adipocytespecific functions of insulin and particularly in the mechanism whereby insulin stimulates phosphorylation of caveolin in 3T3-L1 cells (25,26). Caveolin is an important component of caveolae, flask-shaped invaginations of plasma membranes, which are thought to participate in the processing of intracellular signals.…”

Section: Discussionmentioning

confidence: 99%

“…It remains to be determined whether Sirm co-localizes with FYN in caveolae; however, it is interesting that a significant fraction of cellular Sirm is associated with the plasma membrane in 3T3-L1 adipocytes. Work from the Saltiel laboratory (26) has suggested that Cbl is the kinase responsible for stimulating the adipocyte-specific caveolin kinase activity of FYN. FYN kinase is activated by binding of cellular proteins to its SH2 and SH3 domains.…”

Section: Discussionmentioning

confidence: 99%

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Identification of sirm, a Novel Insulin-regulated SH3 Binding Protein That Associates with Grb-2 and FYN

Salvatore¹,

R.²,

Kido³

et al. 1998

Journal of Biological Chemistry

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We have previously developed a mouse model of insulin-resistant diabetes by targeted inactivation of the insulin receptor gene. During studies of gene expression in livers of insulin receptor-deficient mice, we identified a novel cDNA, which we have termed sirm (Son of Insulin Receptor Mutant mice). sirm is largely, albeit not exclusively, expressed in insulin-responsive tissues. Insulin is a potent modulator of sirm expression, and sirm mRNA levels correlate with tissue sensitivity to insulin. The product of the sirm gene is a serine/threonine-rich protein with several proline-rich motifs and an NPNY motif, conforming to the consensus sequence recognized by the phosphotyrosine binding domains of insulin receptor substrate and Shc proteins. However, Sirm bears no extended homologies with other known proteins. Based on the sequences of the proline-rich domains, we sought to determine whether Sirm binds to the SH3 domains of FYN and Grb-2. We demonstrate here that Sirm binds to FYN and Grb-2 in 3T3-L1 adipocytes and that insulin treatment results in the dissociation of the Sirm⅐FYN and Sirm⅐Grb-2 complexes. We also show that Sirm is a substrate for the kinase activity of FYN in vitro. Based on the patterns of expression of sirm, its regulation by insulin, and the interactions with molecules in the insulin signaling pathway, we surmise that Sirm plays a role in modulating tissue sensitivity to insulin.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Identification of sirm, a Novel Insulin-regulated SH3 Binding Protein That Associates with Grb-2 and FYN

Salvatore¹,

R.²,

Kido³

et al. 1998

Journal of Biological Chemistry

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“…This concentration of signaling molecules suggests that these microdomains might function as a site for compartmentalization of signaling events. We observed that insulin stimulated the tyrosine phosphorylation of c-Cbl (14) and its subsequent translocation to a caveolin-enriched, lipid raft membrane fraction (15,16). The c-Cbl-associated protein (CAP)͞Cbl complex interacts with the insulin receptor and dissociates after insulin stimulation, subsequently migrating to rafts because of the interaction of CAP with the lipid raft-associated protein flotillin (17)(18)(19).…”

mentioning

confidence: 95%

The sorbin homology domain: A motif for the targeting of proteins to lipid rafts

Kimura

Baumann

Chiang

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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141

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On phosphorylation of Cbl, the c-Cbl-associated protein (CAP)͞Cbl complex dissociates from the insulin receptor and translocates to a lipid raft membrane fraction to form a ternary complex with flotillin. Deletion analyses of the CAP gene identified a 115-aa region responsible for flotillin binding. This region is homologous to the peptide sorbin and is referred to as the sorbin homology (SoHo) domain. This domain is present in two other proteins, vinexin and ArgBP2. Vinexin also interacted with flotillin, and deletion of its SoHo domain similarly blocked flotillin binding. The overexpression of a CAP mutant in which the SoHo domain had been deleted (CAP⌬SoHo) prevented the translocation of Cbl to lipid rafts and subsequently blocked the recruitment of CrkII and C3G. Moreover, overexpression of CAP⌬SoHo prevented the stimulation of glucose transport and GLUT4 translocation by insulin. These results suggest a mechanism for localization of signaling proteins to the lipid raft that mediates the compartmentalization of crucial signal transduction pathways.L ipid rafts are microdomains of the plasma membrane enriched in cholesterol and sphingolipids (1, 2). These regions concentrate certain signaling molecules (3, 4), including heterotrimeric and small G proteins (5-7), Src-family tyrosine kinases (8, 9), endothelial nitric oxide synthase (10, 11), G-proteincoupled receptors (12), and certain tyrosine kinase receptors (13). This concentration of signaling molecules suggests that these microdomains might function as a site for compartmentalization of signaling events. We observed that insulin stimulated the tyrosine phosphorylation of c-Cbl (14) and its subsequent translocation to a caveolin-enriched, lipid raft membrane fraction (15, 16). The c-Cbl-associated protein (CAP)͞Cbl complex interacts with the insulin receptor and dissociates after insulin stimulation, subsequently migrating to rafts because of the interaction of CAP with the lipid raft-associated protein flotillin (17)(18)(19). Moreover, the localization of the Cbl͞CAP complex to this microdomain recruits the guanyl nucleotide exchange protein C3G, resulting in the activation of the G protein TC10. This activation of TC10 generates a PI 3-kinaseindependent signal that is crucial to the regulation of glucose uptake by insulin (20,21).CAP is a multifunctional adapter protein with three SH3 domains in its C terminus and a region of homology to the gut peptide sorbin in its N terminus. The overall sorbin homology (SoHo)͞SH3 organization of CAP is also found in other proteins, including vinexin␣ and ArgBP2A. The similar organization of these proteins suggests that they may similarly function as adapters, linking signaling or cytoskeletal proteins to the lipid raft. We demonstrate here that the SoHo domain does indeed mediate the interaction of CAP and vinexin with flotillin. Moreover, this interaction is crucial for the localization of SH3-binding proteins such as Cbl to the lipid raft and propagation of the downstream signal. These data suggest a signaling par...

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“…Evidence from other systems however suggest that this may be the case. c-Cbl has been postulated to regulate the activity of c-Fyn in response to insulin (56), and PRL has been reported to stimulate the formation of a c-Cbl-PI 3-kinase complex with a resultant increase in the c-Cbl-associated PI 3-kinase activity (45). Interestingly, antisense repression of c-Cbl expression enhances the autophosphorylation of the EGF receptor and EGF activation of the JAK-STAT but not the Ras pathway (57), whereas c-Cbl has been reported to be a negative regulator of other kinases such as Syk (58) and ZAP-70 (59).…”

mentioning

confidence: 99%

Growth Hormone Stimulates the Formation of a Multiprotein Signaling Complex Involving p130Cas and CrkII

Zhu¹,

Goh²,

LeRoith³

et al. 1998

Journal of Biological Chemistry

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We have demonstrated previously that growth hormone (GH) activates focal adhesion kinase (FAK), and this activation results in the tyrosine phosphorylation of two FAK substrates, namely paxillin and tensin. We now show here in Chinese hamster ovary cells stably transfected with rat GH receptor cDNA that human (h)GH induces the formation of a large multiprotein signaling complex centered around another FAK-associated protein, p130Cas and the adaptor protein CrkII. hGH stimulates the tyrosine phosphorylation of both p130Cas and CrkII, their association, and the association of multiple other tyrosine-phosphorylated proteins to the complex. Growth hormone (GH)1 is the major regulator of postnatal body growth (1). It possesses diverse and pleiotropic effects on the growth, differentiation, and metabolism of cells. GH is thought to initiate its biological actions, including induction of a number of RNA species in mammalian tissues by interaction with a specific membrane-bound receptor (2). The GH receptor is phosphorylated upon ligand stimulation presumably by the physical association of the nonreceptor tyrosine kinase JAK2 (3). The JAK kinases are linked to transcriptional regulation and JAK activation results in the phosphorylation, dimerization, and nuclear translocation of latent cytoplasmic STAT transcription factors (4). The activated STAT factors bind to their appropriate DNA-responsive elements to activate gene transcription (4). Other diverse actions of GH include the stimulation of chemotaxis and migration of monocytic cells (5). Concordantly, we have demonstrated that GH stimulates the re-organization of the actin cytoskeleton in cells with fibroblastic morphology (6) and reported that this re-organization of the actin cytoskeleton requires the activity of PI 3-kinase.Focal adhesion kinase (p125 FAK ) has been postulated to play a central role in the response of the cell to the extracellular matrix (for review, see Ref. 7) and in cell morphology and motility (for review, see Ref. 8). For example, overexpression of FAK stimulates cell migration (9) and both FAK-deficient endodermal and mesodermal cells migrate slower than their FAK replete counterparts (10, 11). The effect of FAK on the cytoskeleton is presumably mediated by the formation of a p130Cas (Crk-associated substrate)-CrkII complex (12) in association with c-Src (for review, see Ref. 13). We have reported recently that GH stimulates the tyrosine phosphorylation of FAK and two of its substrates, paxillin and tensin, and that FAK associates with JAK2 and requires the JAK2 binding site on the GH receptor for its phosphorylation (14). We demonstrate here that hGH also stimulates the tyrosine phosphorylation of both p130Cas and CrkII, their association, and the association of multiple other tyrosine-phosphorylated proteins to the complex including the c-Src and c-Fyn protein-tyrosine kinases, Nck, c-Cbl, tensin, paxillin, IRS-1, the p85 subunit of PI 3-kinase, SHC, Grb-2, Sos-1, and C3G. Finally we demonstrate that JNK/SAPK is activated in response to ...

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Insulin-stimulated Tyrosine Phosphorylation of Caveolin Is Specific for the Differentiated Adipocyte Phenotype in 3T3-L1 Cells

Cited by 140 publications

References 55 publications

Identification of sirm, a Novel Insulin-regulated SH3 Binding Protein That Associates with Grb-2 and FYN

Identification of sirm, a Novel Insulin-regulated SH3 Binding Protein That Associates with Grb-2 and FYN

The sorbin homology domain: A motif for the targeting of proteins to lipid rafts

Growth Hormone Stimulates the Formation of a Multiprotein Signaling Complex Involving p130Cas and CrkII

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