IL-2, but not IL-4 and other cytokines, induces phosphorylation of a 98-kDa protein associated with SHP-2, phosphatidylinositol 3'-kinase, and Grb2.
Binding of IL-2 to its receptor activates several biochemical pathways, including JAK-STAT, Ras-mitogen-activated protein kinase, and phosphatidylinositol 3'-kinase (PI 3'-kinase) pathways. Recently, it has been shown that the SH2-containing phosphatase, SHP-2, becomes phosphorylated in response to IL-2 stimulation, associates with PI3'-kinase and Grb2, and can exert a positive regulatory role in IL-2 signaling. We now report the identification of a prominent 98-kDa protein (p98) found to be phosphorylated in response to IL-2 stimulation and coprecipitated with SHP-2, the p85 subunit of PI 3'-kinase and Grb2. Interestingly, whereas IL-4 is known to activate PI 3'-kinase, we did not observe any p98 phosphorylation in response to IL-4 stimulation. p98 can form a multipartite complex with all these proteins as immunodepleting with anti-p85 antiserum substantially reduced the amount of p98 immunoprecipitated by SHP-2 and Grb2; the converse was also true. Furthermore, phosphorylation of p98 did not occur in cells lacking JAK3, suggesting that it may be a JAK substrate. Finally, deglycosylation of p98 did not alter its migration, suggesting p98 is not a member of the recently described SHP substrate/signal-regulatory proteins family of transmembrane glycoproteins. Thus p98 is a prominent IL-2-dependent substrate that associates with multiple proteins involved in IL-2 signaling and may play an important role in coupling the different signal transduction pathways activated by IL-2.
Gadina
M
M
Lymphocyte Cell Biology Section, Arthritis and Rheumatism Branch, National Institute of Arthritis Musculoskeletal and Skin Diseases, Bethesda, MD 20892, USA.
Sudarshan
C
C
O'Shea
J J
JJ
D048868:Adaptor Proteins, Signal Transducing; D000943:Antigens, Differentiation; D002478:Cells, Cultured; D016207:Cytokines / Q000502:physiology; D051380:GRB2 Adaptor Protein; D006801:Humans; D007376:Interleukin-2 / Q000502:physiology*; D015847:Interleukin-4 / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D053616:Janus Kinase 3; D007694:Killer Cells, Natural / Q000201:enzymology / Q000378:metabolism; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins / Q000378:metabolism; D008970:Molecular Weight; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010750:Phosphoproteins / Q000096:biosynthesis / Q000378:metabolism; D010766:Phosphorylation; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D011506:Proteins / Q000378:metabolism*; D011971:Receptors, Immunologic; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D015398:Signal Transduction / Q000276:immunology; D013379:Substrate Specificity / Q000276:immunology; D013601:T-Lymphocytes / Q000201:enzymology / Q000378:metabolism; D018909:src Homology Domains / Q000276:immunology*