INSULIN-RECEPTOR SUBSTRATE-2 IS THE MAJOR 170-KDA PROTEIN PHOSPHORYLATED ON TYROSINE IN RESPONSE TO CYTOKINES IN MURINE LYMPHOHEMATOPOIETICCELLS

Insulin receptor substrate 1 (IRS-1), and its structural relative IRS- 2, are both phosphorylated on tyrosine following treatment of cells wi th interleukin-4 (IL-4) and insulin. We have investigated whether both IRS-I and IRS-P are expressed in murine lymphohemopoietic cells. T an d B lymphocytes and macrophages from primary cultures expressed only I RS-2, which became phosphorylated on tyrosine following stimulation wi th both IL-4 and insulin. Likewise, the murine myeloid cell line FD-5 expressed only IRS-2, which was tyrosine phosphorylated in response to IL-4 and insulin, as well as interleukin-3 and granulocyte-macrophage colony stimulating factor. Neither IRS-1 nor IRS-S were expressed at detectable levels in primary bone marrow mast cells although these cel ls do respond to IL-4. Moreover, a factor-dependent lymphocyte cell li ne, CT.4S, which grows continuously in IL-4, did not express detectabl e levels of IRS-1 or IRS-2. IRS-2 from FD-5 cells stimulated with eith er IL-4 or insulin bound to glutathione S-transferase fusion proteins of the p85 subunit of phosphoinositol 3'-kinase, Grb2, and Syp, parall eling reported associations of IRS-1 with these molecules and indicati ng phosphorylation of the corresponding residues on IRS-2.