A Molecular Basis for Insulin Resistance

Tumor necrosis factor α (TNFα) or chronic hyperinsulinemia that induce insulin resistance trigger increased Ser/Thr phosphorylation of the insulin receptor (IR) and of its major insulin receptor substrates, IRS-1 and IRS-2. To unravel the molecular basis for this uncoupling in insulin signaling, we undertook to study the interaction of Ser/Thr-phosphorylated IRS-1 and IRS-2 with the insulin receptor. We could demonstrate that, similar to IRS-1, IRS-2 also interacts with the juxtamembrane (JM) domain (amino acids 943–984) but not with the carboxyl-terminal region (amino acids 1245–1331) of IR expressed in bacteria as His6fusion peptides. Moreover, incubation of rat hepatoma Fao cells with TNFα, bacterial sphingomyelinase, or other Ser(P)/Thr(P)-elevating agents reduced insulin-induced Tyr phosphorylation of IRS-1 and IRS-2, markedly elevated their Ser(P)/Thr(P) levels, and significantly reduced their ability to interact with the JM region of IR. Withdrawal of TNFα for periods as short as 30 min reversed its inhibitory effects on IR-IRS interactions. Similar inhibitory effects were obtained when Fao cells were subjected to prolonged (20–60 min) pretreatment with insulin. Incubation of the cell extracts with alkaline phosphatase reversed the inhibitory effects of insulin. These findings suggest that insulin resistance is associated with enhanced Ser/Thr phosphorylation of IRS-1 and IRS-2, which impairs their interaction with the JM region of IR. Such impaired interactions abolish the ability of IRS-1 and IRS-2 to undergo insulin-induced Tyr phosphorylation and further propagate the insulin receptor signal. Moreover, the reversibility of the TNFα effects and the ability to mimic its action by exogenously added sphingomyelinase argue against the involvement of a proteolytic cascade in mediating the acute inhibitory effects of TNFα on insulin action. Tumor necrosis factor α (TNFα) or chronic hyperinsulinemia that induce insulin resistance trigger increased Ser/Thr phosphorylation of the insulin receptor (IR) and of its major insulin receptor substrates, IRS-1 and IRS-2. To unravel the molecular basis for this uncoupling in insulin signaling, we undertook to study the interaction of Ser/Thr-phosphorylated IRS-1 and IRS-2 with the insulin receptor. We could demonstrate that, similar to IRS-1, IRS-2 also interacts with the juxtamembrane (JM) domain (amino acids 943–984) but not with the carboxyl-terminal region (amino acids 1245–1331) of IR expressed in bacteria as His6fusion peptides. Moreover, incubation of rat hepatoma Fao cells with TNFα, bacterial sphingomyelinase, or other Ser(P)/Thr(P)-elevating agents reduced insulin-induced Tyr phosphorylation of IRS-1 and IRS-2, markedly elevated their Ser(P)/Thr(P) levels, and significantly reduced their ability to interact with the JM region of IR. Withdrawal of TNFα for periods as short as 30 min reversed its inhibitory effects on IR-IRS interactions. Similar inhibitory effects were obtained when Fao cells were subjected to prolonged (20–60 min) pretreatment with insulin. Incubation of the cell extracts with alkaline phosphatase reversed the inhibitory effects of insulin. These findings suggest that insulin resistance is associated with enhanced Ser/Thr phosphorylation of IRS-1 and IRS-2, which impairs their interaction with the JM region of IR. Such impaired interactions abolish the ability of IRS-1 and IRS-2 to undergo insulin-induced Tyr phosphorylation and further propagate the insulin receptor signal. Moreover, the reversibility of the TNFα effects and the ability to mimic its action by exogenously added sphingomyelinase argue against the involvement of a proteolytic cascade in mediating the acute inhibitory effects of TNFα on insulin action. The insulin receptor (IR) 1The abbreviations used are: IR, insulin receptor; IRK, insulin receptor kinase; CT, carboxyl-terminal; JM, juxtamembrane; TNFα, tumor necrosis factor α; SMase, sphingomyelinase; TPA, 12-O-tetradecanoylphorbol-13-acetate; PTB, phosphotyrosine-binding; PAGE, polyacrylamide gel electrophoresis; TNFαR, TNFα receptor. 1The abbreviations used are: IR, insulin receptor; IRK, insulin receptor kinase; CT, carboxyl-terminal; JM, juxtamembrane; TNFα, tumor necrosis factor α; SMase, sphingomyelinase; TPA, 12-O-tetradecanoylphorbol-13-acetate; PTB, phosphotyrosine-binding; PAGE, polyacrylamide gel electrophoresis; TNFαR, TNFα receptor. is an heterotetrameric transmembrane glycoprotein composed of two extracellular α subunits and two transmembrane β subunits linked by disulfide bonds. The α subunits contain the insulin-binding domain while the transmembrane β subunits function as a tyrosine-specific protein kinase (IRK) that undergoes autophosphorylation following insulin binding (reviewed in Ref. 1Cheatham B. Kahn C.R. Endocr. Rev. 1995; 16: 117-142Crossref PubMed Google Scholar). Autophosphorylation activates the IRK (2Zick Y. Kasuga M. Kahn C.R. Roth J. J. Biol. Chem. 1983; 258: 75-80Abstract Full PubMed Google and to protein substrates, J. J. Biol. Chem. Full PubMed Google and the insulin receptor IRS-1 Kahn C.R. PubMed Google and IRS-2 Y. 1995; PubMed Google to further propagate the insulin signal. IRS-1 and IRS-2, two protein of IRK, a which a domain and a and a with phosphorylation IRS-1 and IRS-2 also contain 30 Ser/Thr in phosphorylation Kahn C.R. PubMed Google Y. 1995; PubMed Google Scholar). The of IRS-1 and IRS-2 in mediating insulin action is IRS-2 as an of IR in IRS-1 Kahn C.R. J. Biol. Chem. 1995; Full Full PubMed Google which a of insulin resistance is a in which cells to to of insulin J. Scholar). the molecular impaired insulin or of the insulin receptor or of its major to insulin action is to agents that Ser/Thr phosphorylation of the receptor or of its which IRK or its ability to Y. Rev. Biol. PubMed Google and PubMed Google for as or levels, the protein and the Ser(P)/Thr(P) of the insulin which in an an of protein insulin-induced Tyr phosphorylation of IRS-1 while the Ser/Thr phosphorylation of this protein Y. J. Biol. Chem. Full PubMed Google J. Biol. Chem. Full Full PubMed Google Scholar). Tumor necrosis a of insulin resistance in tumor and also in a similar TNFα insulin-induced Tyr phosphorylation of IRS-1 while Ser/Thr phosphorylation of IRS-1, which its J. Biol. Chem. 1995; Full Full PubMed Google PubMed Google Scholar). These effects of TNFα not the of increased phosphatase but of or of J. Biol. Chem. 1995; Full Full PubMed Google Scholar). The effects of TNFα by cells with sphingomyelinase or of J. Biol. Chem. Full Full PubMed Google J. Biol. Chem. Full Full PubMed Google that TNFα the Full PubMed Google J. M. Full Full PubMed Google to insulin action. findings suggest the of for IR and IRS-1 that Ser/Thr phosphorylation of is Ser/Thr phosphorylation of IR or its their interactions and is the of of the in this to the in insulin is to in in agents that Ser/Thr phosphorylation IR and its impaired could enhanced Ser/Thr phosphorylation of IR its IRS-1 and or the study we undertook to this by the effects of Ser/Thr phosphorylation of IR, on in Ser(P)/Thr(P) of IRS-1 and IRS-2. We of findings that the juxtamembrane (JM) domain of IR (amino acids not its carboxyl-terminal region (amino acids to interactions IR and IRS-1 Y. J. Biol. Chem. Full Full PubMed Google Scholar). we that similar to IRS-1, IRS-2 also interacts with the JM but not the region of IR. Moreover, TNFα, and other agents significantly the ability of IRS-1 or IRS-2 to interact with the JM region of IR. Such impaired interactions abolish the ability of IRS-1 and IRS-2 to undergo insulin-induced Tyr phosphorylation and further propagate the insulin receptor with a molecular for the of an this study we that insulin resistance the molecular is in by enhanced Ser/Thr phosphorylation of IRS-1 and IRS-2, which their interaction with the juxtamembrane region of the insulin receptor that to undergo Tyr Tyr phosphorylation the ability of IRS-1 and IRS-2 to as J. Biol. Chem. 1995; Full Full PubMed Google and in of insulin of a we could demonstrate that IRS-2, IRS-1, interacts with the JM region of IR but not with its Moreover, the JM, but not the with binding of the to the JM in with PubMed Google J. Biol. Chem. Full Full PubMed Google J. Biol. Chem. 1995; Full Full PubMed Google J. Biol. Chem. Full Full PubMed Google B. J. Biol. Chem. Full PubMed Google PubMed Google B. M. B. J. PubMed Google we that agents as TNFα, SMase, TPA, and to insulin the Ser(P)/Thr(P) of IRS-1 and IRS-2, as by a in their we an the of Ser/Thr phosphorylation of IRS-1 and IRS-2 by their reduced and the ability of to interact with the JM region of IR. we were to demonstrate the reversibility of with to TNFα, the involvement of in the of Ser/Thr phosphorylation in the of IRS-1 and IRS-2 to the JM phosphorylation of a by insulin and other is the in insulin in to TNFα, the to a and a to insulin resistance J. Biol. Chem. Full Full PubMed Google J. Biol. Chem. Full Full PubMed Google Full Google Full Full PubMed Google Scholar). TNFα with a to two J. M. Full Full PubMed Google Biol. 1995; Full PubMed Google Scholar). These and transmembrane of that with J. 1995; Full PubMed Google Scholar). of is to by TNFα, J. Rev. PubMed Google Scholar). of the TNFα to to to of the as to the of an cascade Full Full PubMed Google M. Full Full PubMed Google two other and kinase and M. Full Full PubMed Google Scholar). a protein a to J. M. Full Full PubMed Google in the of Biol. 1995; Full PubMed Google which in activates Full PubMed Google J. Biol. Chem. Full PubMed Google M. J. J. 1995; PubMed Google Scholar). of J. Biol. Chem. Full Full PubMed Google which impairs IR-IRS min of TNFα of Fao that TNFα insulin resistance in cells of an Moreover, TNFα effects by bacterial and in involvement of SMase, and not Tyr phosphorylation of IRS-2 in cells IR and IRS-2 J. Biol. Chem. Full Full PubMed Google Scholar). These to the that IRS-1 but not IRS-2 is in the by which TNFα, SMase, and insulin J. Biol. Chem. Full Full PubMed Google Scholar). to the that the insulin-induced Tyr phosphorylation of IRS-1 and IRS-2, as as their interactions with IR subjected to by TNFα or by The for is but could for by the that were in rat hepatoma cells that of the for of IRS-2 is which were not to to insulin as as with IRS-1 Y. 1995; PubMed Google Scholar). interact with of the insulin the of and Y. 1995; PubMed Google Kahn C.R. J. Biol. Chem. 1995; Full Full PubMed Google Scholar). Moreover, IRS-2 as an of the IR in Y. 1995; PubMed Google Scholar). of the two that IRS-2, IRS-1, is subjected to by TNFα and other Ser(P)/Thr(P) in hepatoma that the of Ser/Thr phosphorylation TNFα IRS-1 to an of IRK J. Biol. Chem. Full Full PubMed Google Scholar). an for the of Ser/Thr-phosphorylated IRS-1 and IRS-2. to insulin resistance is associated with enhanced Ser/Thr phosphorylation of IRS-1 and IRS-2, which in impaired interaction of with the insulin receptor. Such impaired interaction the ability of to undergo insulin-induced Tyr phosphorylation and further propagate the insulin of of IR-IRS interactions is not in of the that in the ability to Ser(P)/Thr(P) induce insulin TNFα or TPA, of as or Ser(P)/Thr(P) of protein of cells to insulin the Ser(P)/Thr(P) of IRS-1 and IRS-2 and their interaction with the JM is the that the reduced binding of IRS-1 and IRS-2 to the JM in cells a when with their of insulin-induced Tyr These findings with the that insulin-induced of Ser/Thr when with the of the IRK and the Tyr phosphorylation of its further suggest that of in the of enhanced Ser/Thr phosphorylation and of is to with a for the insulin to propagate is The of this is by the that protein of this in of Ser/Thr phosphorylation on IRS-1 and IRS-2 the of in impaired IR-IRS interactions a of the IRS-1 and IRS-2, a which IRS-1 and IRS-2, their interactions with the JM region of IR Full Full PubMed Google Scholar). of the (amino acids of IRS-1 and acids of IRS-2 Y. 1995; PubMed Google the of Ser/Thr phosphorylation the interactions of the domain with the JM that IRS-2 interacts with IR an domain (amino acids that to the kinase region of IR J. Biol. Chem. Full Full PubMed Google Scholar). the of this domain to the interactions not in the the IRS-2 phosphorylation and interactions of this protein with the JM region that the domain a to the interactions. that with of J. J. Biol. Chem. Full Full PubMed Google that of the domain the ability of IRS-1 to undergo phosphorylation in The for the could to the that the in which IRS-1 while insulin of and phosphorylation of IRS-1 when an domain for as the is of insulin Tyr phosphorylation of IRS-1 is impaired J. J. Biol. Chem. Full Full PubMed Google of the domain of IRS-1 impairs its ability to undergo phosphorylation in cells Y. J. Biol. Chem. 1995; Full Full PubMed Google its ability to interact with the JM in Y. J. Biol. Chem. Full Full PubMed Google Scholar). the and domain to interactions in IRS-1 or IRS-2, on Tyr or Ser/Thr to the JM is with the that on Tyr the receptor to other to further propagate the insulin signal. Ser/Thr phosphorylation with binding of IRS-1 or IRS-2 to the JM region and their Tyr phosphorylation to a to insulin receptor and Ser/Thr by insulin as that and induce a that the interactions and the JM region of IR. Ser(P)/Thr(P)-elevating agents the to insulin and an insulin-induced Ser/Thr phosphorylation of in the of and of the kinase cascade J. Biol. Chem. 1995; Full Full PubMed Google J. Biol. Chem. Full Full PubMed Google Scholar). the two major insulin by and by subjected to in the of Ser/Thr in this the of insulin as the of The insulin receptor (IR) 1The abbreviations used are: IR, insulin receptor; IRK, insulin receptor kinase; CT, carboxyl-terminal; JM, juxtamembrane; TNFα, tumor necrosis factor α; SMase, sphingomyelinase; TPA, 12-O-tetradecanoylphorbol-13-acetate; PTB, phosphotyrosine-binding; PAGE, polyacrylamide gel electrophoresis; TNFαR, TNFα receptor. 1The abbreviations used are: IR, insulin receptor; IRK, insulin receptor kinase; CT, carboxyl-terminal; JM, juxtamembrane; TNFα, tumor necrosis factor α; SMase, sphingomyelinase; TPA, 12-O-tetradecanoylphorbol-13-acetate; PTB, phosphotyrosine-binding; PAGE, polyacrylamide gel electrophoresis; TNFαR, TNFα receptor. is an heterotetrameric transmembrane glycoprotein composed of two extracellular α subunits and two transmembrane β subunits linked by disulfide bonds. The α subunits contain the insulin-binding domain while the transmembrane β subunits function as a tyrosine-specific protein kinase (IRK) that undergoes autophosphorylation following insulin binding (reviewed in Ref. 1Cheatham B. Kahn C.R. Endocr. Rev. 1995; 16: 117-142Crossref PubMed Google Scholar). Autophosphorylation activates the IRK (2Zick Y. Kasuga M. Kahn C.R. Roth J. J. Biol. Chem. 1983; 258: 75-80Abstract Full PubMed Google and to protein substrates, J. J. Biol. Chem. Full PubMed Google and the insulin receptor IRS-1 Kahn C.R. PubMed Google and IRS-2 Y. 1995; PubMed Google to further propagate the insulin signal. IRS-1 and IRS-2, two protein of IRK, a which a domain and a and a with phosphorylation IRS-1 and IRS-2 also contain 30 Ser/Thr in phosphorylation Kahn C.R. PubMed Google Y. 1995; PubMed Google Scholar). The of IRS-1 and IRS-2 in mediating insulin action is IRS-2 as an of IR in IRS-1 Kahn C.R. J. Biol. Chem. 1995; Full Full PubMed Google which a of insulin resistance is a in which cells to to of insulin J. Scholar). the molecular impaired insulin or of the insulin receptor or of its major to insulin action is to agents that Ser/Thr phosphorylation of the receptor or of its which IRK or its ability to Y. Rev. Biol. PubMed Google and PubMed Google for as or levels, the protein and the Ser(P)/Thr(P) of the insulin which in an an of protein insulin-induced Tyr phosphorylation of IRS-1 while the Ser/Thr phosphorylation of this protein Y. J. Biol. Chem. Full PubMed Google J. Biol. Chem. Full Full PubMed Google Scholar). Tumor necrosis a of insulin resistance in tumor and also in a similar TNFα insulin-induced Tyr phosphorylation of IRS-1 while Ser/Thr phosphorylation of IRS-1, which its J. Biol. Chem. 1995; Full Full PubMed Google PubMed Google Scholar). These effects of TNFα not the of increased phosphatase but of or of J. Biol. Chem. 1995; Full Full PubMed Google Scholar). The effects of TNFα by cells with sphingomyelinase or of J. Biol. Chem. Full Full PubMed Google J. Biol. Chem. Full Full PubMed Google that TNFα the Full PubMed Google J. M. Full Full PubMed Google to insulin action. findings suggest the of for IR and IRS-1 that Ser/Thr phosphorylation of is Ser/Thr phosphorylation of IR or its their interactions and is the of of the in this to the in insulin is to in in agents that Ser/Thr phosphorylation IR and its impaired could enhanced Ser/Thr phosphorylation of IR its IRS-1 and or the study we undertook to this by the effects of Ser/Thr phosphorylation of IR, on in Ser(P)/Thr(P) of IRS-1 and IRS-2. We of findings that the juxtamembrane (JM) domain of IR (amino acids not its carboxyl-terminal region (amino acids to interactions IR and IRS-1 Y. J. Biol. Chem. Full Full PubMed Google Scholar). we that similar to IRS-1, IRS-2 also interacts with the JM but not the region of IR. Moreover, TNFα, and other agents significantly the ability of IRS-1 or IRS-2 to interact with the JM region of IR. Such impaired interactions abolish the ability of IRS-1 and IRS-2 to undergo insulin-induced Tyr phosphorylation and further propagate the insulin receptor with a molecular for the of an this study we that insulin resistance the molecular is in by enhanced Ser/Thr phosphorylation of IRS-1 and IRS-2, which their interaction with the juxtamembrane region of the insulin receptor that to undergo Tyr Tyr phosphorylation the ability of IRS-1 and IRS-2 to as J. Biol. Chem. 1995; Full Full PubMed Google and in of insulin of a we could demonstrate that IRS-2, IRS-1, interacts with the JM region of IR but not with its Moreover, the JM, but not the with binding of the to the JM in with PubMed Google J. Biol. Chem. Full Full PubMed Google J. Biol. Chem. 1995; Full Full PubMed Google J. Biol. Chem. Full Full PubMed Google B. J. Biol. Chem. Full PubMed Google PubMed Google B. M. B. J. PubMed Google we that agents as TNFα, SMase, TPA, and to insulin the Ser(P)/Thr(P) of IRS-1 and IRS-2, as by a in their we an the of Ser/Thr phosphorylation of IRS-1 and IRS-2 by their reduced and the ability of to interact with the JM region of IR. we were to demonstrate the reversibility of with to TNFα, the involvement of in the of Ser/Thr phosphorylation in the of IRS-1 and IRS-2 to the JM phosphorylation of a by insulin and other is the in insulin in to TNFα, the to a and a to insulin resistance J. Biol. Chem. Full Full PubMed Google J. Biol. Chem. Full Full PubMed Google Full Google Full Full PubMed Google Scholar). TNFα with a to two J. M. Full Full PubMed Google Biol. 1995; Full PubMed Google Scholar). These and transmembrane of that with J. 1995; Full PubMed Google Scholar). of is to by TNFα, J. Rev. PubMed Google Scholar). of the TNFα to to to of the as to the of an cascade Full Full PubMed Google M. Full Full PubMed Google two other and kinase and M. Full Full PubMed Google Scholar). a protein a to J. M. Full Full PubMed Google in the of Biol. 1995; Full PubMed Google which in activates Full PubMed Google J. Biol. Chem. Full PubMed Google M. J. J. 1995; PubMed Google Scholar). of J. Biol. Chem. Full Full PubMed Google which impairs IR-IRS min of TNFα of Fao that TNFα insulin resistance in cells of an Moreover, TNFα effects by bacterial and in involvement of SMase, and not Tyr phosphorylation of IRS-2 in cells IR and IRS-2 J. Biol. Chem. Full Full PubMed Google Scholar). These to the that IRS-1 but not IRS-2 is in the by which TNFα, SMase, and insulin J. Biol. Chem. Full Full PubMed Google Scholar). to the that the insulin-induced Tyr phosphorylation of IRS-1 and IRS-2, as as their interactions with IR subjected to by TNFα or by The for is but could for by the that were in rat hepatoma cells that of the for of IRS-2 is which were not to to insulin as as with IRS-1 Y. 1995; PubMed Google Scholar). interact with of the insulin the of and Y. 1995; PubMed Google Kahn C.R. J. Biol. Chem. 1995; Full Full PubMed Google Scholar). Moreover, IRS-2 as an of the IR in Y. 1995; PubMed Google Scholar). of the two that IRS-2, IRS-1, is subjected to by TNFα and other Ser(P)/Thr(P) in hepatoma that the of Ser/Thr phosphorylation TNFα IRS-1 to an of IRK J. Biol. Chem. Full Full PubMed Google Scholar). an for the of Ser/Thr-phosphorylated IRS-1 and IRS-2. to insulin resistance is associated with enhanced Ser/Thr phosphorylation of IRS-1 and IRS-2, which in impaired interaction of with the insulin receptor. Such impaired interaction the ability of to undergo insulin-induced Tyr phosphorylation and further propagate the insulin of of IR-IRS interactions is not in of the that in the ability to Ser(P)/Thr(P) induce insulin TNFα or TPA, of as or Ser(P)/Thr(P) of protein of cells to insulin the Ser(P)/Thr(P) of IRS-1 and IRS-2 and their interaction with the JM is the that the reduced binding of IRS-1 and IRS-2 to the JM in cells a when with their of insulin-induced Tyr These findings with the that insulin-induced of Ser/Thr when with the of the IRK and the Tyr phosphorylation of its further suggest that of in the of enhanced Ser/Thr phosphorylation and of is to with a for the insulin to propagate is The of this is by the that protein of this in of Ser/Thr phosphorylation on IRS-1 and IRS-2 the of in impaired IR-IRS interactions a of the IRS-1 and IRS-2, a which IRS-1 and IRS-2, their interactions with the JM region of IR Full Full PubMed Google Scholar). of the (amino acids of IRS-1 and acids of IRS-2 Y. 1995; PubMed Google the of Ser/Thr phosphorylation the interactions of the domain with the JM that IRS-2 interacts with IR an domain (amino acids that to the kinase region of IR J. Biol. Chem. Full Full PubMed Google Scholar). the of this domain to the interactions not in the the IRS-2 phosphorylation and interactions of this protein with the JM region that the domain a to the interactions. that with of J. J. Biol. Chem. Full Full PubMed Google that of the domain the ability of IRS-1 to undergo phosphorylation in The for the could to the that the in which IRS-1 while insulin of and phosphorylation of IRS-1 when an domain for as the is of insulin Tyr phosphorylation of IRS-1 is impaired J. J. Biol. Chem. Full Full PubMed Google of the domain of IRS-1 impairs its ability to undergo phosphorylation in cells Y. J. Biol. Chem. 1995; Full Full PubMed Google its ability to interact with the JM in Y. J. Biol. Chem. Full Full PubMed Google Scholar). the and domain to interactions in IRS-1 or IRS-2, on Tyr or Ser/Thr to the JM is with the that on Tyr the receptor to other to further propagate the insulin signal. Ser/Thr phosphorylation with binding of IRS-1 or IRS-2 to the JM region and their Tyr phosphorylation to a to insulin receptor and Ser/Thr by insulin as that and induce a that the interactions and the JM region of IR. Ser(P)/Thr(P)-elevating agents the to insulin and an insulin-induced Ser/Thr phosphorylation of in the of and of the kinase cascade J. Biol. Chem. 1995; Full Full PubMed Google J. Biol. Chem. Full Full PubMed Google Scholar). the two major insulin by and by subjected to in the of Ser/Thr in this the of insulin as the of this study we that insulin resistance the molecular is in by enhanced Ser/Thr phosphorylation of IRS-1 and IRS-2, which their interaction with the juxtamembrane region of the insulin receptor that to undergo Tyr Tyr phosphorylation the ability of IRS-1 and IRS-2 to as J. Biol. Chem. 1995; Full Full PubMed Google and in of insulin of a we could demonstrate that IRS-2, IRS-1, interacts with the JM region of IR but not with its Moreover, the JM, but not the with binding of the to the JM in with PubMed Google J. Biol. Chem. Full Full PubMed Google J. Biol. Chem. 1995; Full Full PubMed Google J. Biol. Chem. Full Full PubMed Google B. J. Biol. Chem. Full PubMed Google PubMed Google B. M. B. J. PubMed Google we that agents as TNFα, SMase, TPA, and to insulin the Ser(P)/Thr(P) of IRS-1 and IRS-2, as by a in their we an the of Ser/Thr phosphorylation of IRS-1 and IRS-2 by their reduced and the ability of to interact with the JM region of IR. we were to demonstrate the reversibility of with to TNFα, the involvement of in the of Ser/Thr phosphorylation in the of IRS-1 and IRS-2 to the JM Ser/Thr phosphorylation of a by insulin and other is the in insulin in to TNFα, the to a and a to insulin resistance J. Biol. Chem. Full Full PubMed Google J. Biol. Chem. Full Full PubMed Google Full Google Full Full PubMed Google Scholar). TNFα with a to two J. M. Full Full PubMed Google Biol. 1995; Full PubMed Google Scholar). These and transmembrane of that with J. 1995; Full PubMed Google Scholar). of is to by TNFα, J. Rev. PubMed Google Scholar). of the TNFα to to to of the as to the of an cascade Full Full PubMed Google M. Full Full PubMed Google two other and kinase and M. Full Full PubMed Google Scholar). a protein a to J. M. Full Full PubMed Google in the of Biol. 1995; Full PubMed Google which in activates Full PubMed Google J. Biol. Chem. Full PubMed Google M. J. J. 1995; PubMed Google Scholar). of J. Biol. Chem. Full Full PubMed Google which impairs IR-IRS min of TNFα of Fao that TNFα insulin resistance in cells of an Moreover, TNFα effects by bacterial and in involvement of TNFα, SMase, and not Tyr phosphorylation of IRS-2 in cells IR and IRS-2 J. Biol. Chem. Full Full PubMed Google Scholar). These to the that IRS-1 but not IRS-2 is in the by which TNFα, SMase, and insulin J. Biol. Chem. Full Full PubMed Google Scholar). to the that the insulin-induced Tyr phosphorylation of IRS-1 and IRS-2, as as their interactions with IR subjected to by TNFα or by The for is but could for by the that were in rat hepatoma cells that of the for of IRS-2 is which were not to to insulin IRS-2 as as with IRS-1 Y. 1995; PubMed Google Scholar). interact with of the insulin the of and Y. 1995; PubMed Google Kahn C.R. J. Biol. Chem. 1995; Full Full PubMed Google Scholar). Moreover, IRS-2 as an of the IR in Y. 1995; PubMed Google Scholar). of the two that IRS-2, IRS-1, is subjected to by TNFα and other Ser(P)/Thr(P) in hepatoma that the of Ser/Thr phosphorylation TNFα IRS-1 to an of IRK J. Biol. Chem. Full Full PubMed Google Scholar). an for the of Ser/Thr-phosphorylated IRS-1 and IRS-2. to insulin resistance is associated with enhanced Ser/Thr phosphorylation of IRS-1 and IRS-2, which in impaired interaction of with the insulin receptor. Such impaired interaction the ability of to undergo insulin-induced Tyr phosphorylation and further propagate the insulin signal. The of of IR-IRS interactions is not in of the that in the ability to Ser(P)/Thr(P) induce insulin TNFα or TPA, of as or Ser(P)/Thr(P) of protein of cells to insulin the Ser(P)/Thr(P) of IRS-1 and IRS-2 and their interaction with the JM is the that the reduced binding of IRS-1 and IRS-2 to the JM in cells a when with their of insulin-induced Tyr These findings with the that insulin-induced of Ser/Thr when with the of the IRK and the Tyr phosphorylation of its further suggest that of in the of enhanced Ser/Thr phosphorylation and of is to with a for the insulin to propagate is The of this is by the that protein of this in The of Ser/Thr phosphorylation on IRS-1 and IRS-2 the of in impaired IR-IRS interactions a of the IRS-1 and IRS-2, a which IRS-1 and IRS-2, their interactions with the JM region of IR Full Full PubMed Google Scholar). of the (amino acids of IRS-1 and acids of IRS-2 Y. 1995; PubMed Google the of Ser/Thr phosphorylation the interactions of the domain with the JM that IRS-2 interacts with IR an domain (amino acids that to the kinase region of IR J. Biol. Chem. Full Full PubMed Google Scholar). the of this domain to the interactions not in the the IRS-2 phosphorylation and interactions of this protein with the JM region that the domain a to the interactions. that with of J. J. Biol. Chem. Full Full PubMed Google that of the domain the ability of IRS-1 to undergo phosphorylation in The for the could to the that the in which IRS-1 while insulin of and phosphorylation of IRS-1 when an domain for as the is of insulin Tyr phosphorylation of IRS-1 is impaired J. J. Biol. Chem. Full Full PubMed Google Scholar). of the domain of IRS-1 impairs its ability to undergo phosphorylation in cells Y. J. Biol. Chem. 1995; Full Full PubMed Google its ability to interact with the JM in Y. J. Biol. Chem. Full Full PubMed Google Scholar). the and domain to interactions in IRS-1 or IRS-2, on Tyr or Ser/Thr to the JM is with the that on Tyr the receptor to other to further propagate the insulin signal. Ser/Thr phosphorylation with binding of IRS-1 or IRS-2 to the JM region and their Tyr Ser/Thr phosphorylation to a to insulin receptor and Ser/Thr by insulin as that and induce a that the interactions and the JM region of IR. Ser(P)/Thr(P)-elevating agents the to insulin and an insulin-induced Ser/Thr phosphorylation of in the of and of the kinase cascade J. Biol. Chem. 1995; Full Full PubMed Google J. Biol. Chem. Full Full PubMed Google Scholar). the two major insulin by and by subjected to in the of Ser/Thr in this the of insulin as the of We and for and We for in the