TY - JOUR
T1 - Enhancement or inhibition of insulin signaling by insulin receptor substrate 1 is cell context dependent
AU - Yamauchi, Keishi
AU - Pessin, Jeffrey E.
PY - 1994/7
Y1 - 1994/7
N2 - Insulin treatment of Chinese hamster ovary (CHO) cells expressing high levels of the insulin receptor (CHO/IR cells) activates both c-fos serum response element and activator protein 1 (AP-1) reporter genes approximately 10-fold. In contrast, parental CHO cells display only two- to threefold insulin stimulation of reporter gene activity. Transient transfection of parental CHO cells with an insulin receptor substrate 1 (IRS1) expression plasmid enhanced insulin downstream signaling in a biphasic manner, whereas IRS1 transfection of CHO/IR cells inhibited insulin signaling in a dose- dependent fashion. Further, expression of Grb2 in parental CHO cells had no effect on insulin signaling, whereas Grb2 increased insulin activation of reporter gene expression in CHO/IR cells. These data suggest that the expression levels of various effector molecules can either enhance or inhibit insulin downstream signaling events. To assess the relative effects of various insulin receptor, IRS1, and Grb2 levels on insulin signaling, parental CHO cells were transiently transfected with various combinations of expression plasmids encoding these proteins. Although expression of IRS1 resulted in a biphasic increase of insulin signaling in parental CHO cells, coexpression of IRS1 with the insulin receptor resulted in inhibition of signaling. This inhibition of insulin signaling directly correlated with an increased association of Grb2 with IRS1 and a concomitant sequestration of Grb2 away from Shc. Consistent with the Shc-Grb2 pathway as the major route for insulin-stimulated c-Fos and AP-1 transcriptional activation, the IRS1- mediated inhibition was reversed by transfection with an expression plasmid for Grb2. These data demonstrate that the extent of insulin-stimulated downstream signaling was dependent not only on the levels of individual signaling molecules but also on the formation of multiprotein complexes with specific stoichiometries.
AB - Insulin treatment of Chinese hamster ovary (CHO) cells expressing high levels of the insulin receptor (CHO/IR cells) activates both c-fos serum response element and activator protein 1 (AP-1) reporter genes approximately 10-fold. In contrast, parental CHO cells display only two- to threefold insulin stimulation of reporter gene activity. Transient transfection of parental CHO cells with an insulin receptor substrate 1 (IRS1) expression plasmid enhanced insulin downstream signaling in a biphasic manner, whereas IRS1 transfection of CHO/IR cells inhibited insulin signaling in a dose- dependent fashion. Further, expression of Grb2 in parental CHO cells had no effect on insulin signaling, whereas Grb2 increased insulin activation of reporter gene expression in CHO/IR cells. These data suggest that the expression levels of various effector molecules can either enhance or inhibit insulin downstream signaling events. To assess the relative effects of various insulin receptor, IRS1, and Grb2 levels on insulin signaling, parental CHO cells were transiently transfected with various combinations of expression plasmids encoding these proteins. Although expression of IRS1 resulted in a biphasic increase of insulin signaling in parental CHO cells, coexpression of IRS1 with the insulin receptor resulted in inhibition of signaling. This inhibition of insulin signaling directly correlated with an increased association of Grb2 with IRS1 and a concomitant sequestration of Grb2 away from Shc. Consistent with the Shc-Grb2 pathway as the major route for insulin-stimulated c-Fos and AP-1 transcriptional activation, the IRS1- mediated inhibition was reversed by transfection with an expression plasmid for Grb2. These data demonstrate that the extent of insulin-stimulated downstream signaling was dependent not only on the levels of individual signaling molecules but also on the formation of multiprotein complexes with specific stoichiometries.
UR - http://www.scopus.com/inward/record.url?scp=0028226039&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0028226039&partnerID=8YFLogxK
U2 - 10.1128/MCB.14.7.4427
DO - 10.1128/MCB.14.7.4427
M3 - Article
C2 - 8007950
AN - SCOPUS:0028226039
SN - 0270-7306
VL - 14
SP - 4427
EP - 4434
JO - Molecular and cellular biology
JF - Molecular and cellular biology
IS - 7
ER -