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Molecular and Cellular Biology, November 1998, p. 6784-6794, Vol. 18, No. 11
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

The Pleckstrin Homology and Phosphotyrosine Binding Domains of Insulin Receptor Substrate 1 Mediate Inhibition of Apoptosis by Insulin

Lynne Yenush, Christine Zanella, Tohru Uchida, Dolores Bernal,dagger and Morris F. White

Howard Hughes Medical Institute, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts 02215

Received 20 April 1998/Returned for modification 8 June 1998/Accepted 13 August 1998

Insulin and insulin-like growth factor 1 (IGF-1) evoke diverse biological effects through receptor-mediated tyrosine phosphorylation of insulin receptor substrate (IRS) proteins. We investigated the elements of IRS-1 signaling that inhibit apoptosis of interleukin 3 (IL-3)-deprived 32D myeloid progenitor cells. 32D cells have few insulin receptors and no IRS proteins; therefore, insulin failed to inhibit apoptosis during IL-3 withdrawal. Insulin stimulated mitogen-activated protein kinase in 32D cells expressing insulin receptors (32DIR) but failed to activate the phosphatidylinositol 3 (PI 3)-kinase cascade or to inhibit apoptosis. By contrast, insulin stimulated the PI 3-kinase cascade, inhibited apoptosis, and promoted replication of 32DIR cells expressing IRS-1. As expected, insulin did not stimulate PI 3-kinase in 32DIR cells, which expressed a truncated IRS-1 protein lacking the tail of tyrosine phosphorylation sites. However, this truncated IRS-1 protein, which retained the NH2-terminal pleckstrin homology (PH) and phosphotyrosine binding (PTB) domains, mediated phosphorylation of PKB/akt, inhibition of apoptosis, and replication of 32DIR cells during insulin stimulation. These results suggest that a phosphotyrosine-independent mechanism mediated by the PH and PTB domains promoted antiapoptotic and growth actions of insulin. Although PI 3-kinase was not activated, its phospholipid products were required, since LY294002 inhibited these responses. Without IRS-1, a chimeric insulin receptor containing a tail of tyrosine phosphorylation sites derived from IRS-1 activated the PI 3-kinase cascade but failed to inhibit apoptosis. Thus, phosphotyrosine-independent IRS-1-linked pathways may be critical for survival and growth of IL-3-deprived 32D cells during insulin stimulation.

dagger Present address: Departament de Bioquimica i Biologia Molecular, Facultat de Ciencies Biologiques, 46100-Burjassot, Valencia, Spain.

Molecular and Cellular Biology, November 1998, p. 6784-6794, Vol. 18, No. 11
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


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