Janus Kinase-dependent Activation of Insulin Receptor Substrate 1 in Response to Interleukin-4, Oncostatin M, and the Interferons

Abstract

In addition to a role in response to insulin and insulinlike growth factors, insulin receptor substrate 1 (IRS-1) is phosphorylated in response to IL-4, the interferons (IFNs) and oncostatin M (OSM). Here mutant cell lines lacking JAK1, JAK2, or Tyk2 were used to determine the role(s) of the Janus kinase (JAK) family of protein-tyrosine kinases in IRS-1 phophorylation. 32D cells, which do not express IRS proteins, were analyzed for any requirement for these proteins in response to the IFNs. For the mutant human fibrosarcoma cell lines, phosphorylation of IRS-1 through the insulin-like growth factor receptor is independent of JAK1, JAK2, or Tyk2. In contrast, phosphorylation of IRS-1 mediated by the Type I IFNs, IL-4, and OSM is JAK-dependent. For the ␣␤-IFNs, activation of IRS-1 is dependent on JAK1 and Tyk2, consistent with the interdependence of these kinases in the IFN-␣␤ response. Neither IRS-1 nor IRS-2 was detectably activated by IFN-␥. Consistent with this, activation of neither IRS proteins appears to be an absolute requirement for an antiproliferative or an antiviral response to the IFNs. For IL-4 and OSM phosphorylation of IRS-1 in the human fibrosarcoma cells is largely dependent on JAK1 but can also be mediated through Tyk2 or JAK2. Activation of phosphatidylinositol 3 -kinase in response to IL-4 and OSM, at least, was also JAK-dependent. The JAKs are, therefore, required not only for STAT activation but also for the activation, through a variety of different types of cytokine receptor, of an additional signaling pathway(s) through IRS-1 and phosphatidylinositol 3 -kinase.Receptors that have an intrinsic tyrosine kinase domain recruit and activate a variety of signal transducers. Insulin receptor substrate 1 (IRS-1) 1 is a cytosolic protein of ϳ180 kDa in mass that is tyrosyl-phosphorylated at multiple sites through activated insulin and insulin-like growth factor 1 (IGF-1) receptors (1, 2). An L(X) 4 NPXY(p)XSXP motif has been identified in the insulin receptor as being important for the recruitment of the IRS proteins. IRS-1 contains multiple YMXM and YXXM tyrosine motifs, which when phosphorylated can recruit Src homology 2 domain-containing proteins, including the p85␣ regulatory subunit of PI 3Ј-kinase, SHP-2, Grb-2, Crk, and Nck (3, 4). Phosphorylated IRS-1, therefore, can mediate a variety of responses including a mitogenic response and activation of PI 3Ј-kinase.Common themes involving the role of tyrosine kinases and proteins with Src homology 2 domains have emerged to describe broadly the mechanism of signal transduction by many growth factors and cytokines. Signal transduction pathways utilizing the JAK (Janus kinase) family of protein-tyrosine kinases and the STATs (signal transducers and activators of transcription) are activated in response to polypeptide ligands including many cytokines, some growth factors and the interferons (IFNs). STAT activation mediated through the JAKs occurs in receptor complexes at the cell membrane. There are four known mammalian JAKs: JAK1, JAK2, JAK3, and T...

STAT-1 Mediates the Stimulatory Effect of IL-10 on CD14 Expression in Human Monocytic Cells

“…For example, JAK1 activated by either IL-4, IFN-␣, IL-10, or Oncostatin-M activates the p85 subunit of PI3K through tyrosine phosphorylation of the IRS-1 docking molecule (23,24). In this study, IL-10 stimulation of monocytic cells induced the activation of the survival enzyme, Akt-1, the signaling molecule downstream of PI3K.…”

“…For example, IL-10 induced the activation of PI3K (22,23) possibly through JAK-1 activation. There is evidence to suggest that JAK1 phosphorylates the insulin receptor substrate-1 (IRS-1) docking molecule following interaction of IL-2, IL-4, IL-10, and IFN-␣ with their corresponding receptors (23,24). Subsequently, tyrosine-phosphorylated IRS-1 proteins may recruit the regulatory p85 subunit of PI3K to the plasma membrane through phospho-tyrosine-SH2 domain interactions (25).…”

Dimerization of the Interferon Type I Receptor IFNaR2–2 Is Sufficient for Induction of Interferon Effector Genes but Not for Full Antiviral Activity

“…However, as it has been demonstrated that phosphorylation of tyrosine residues in the IFNaR1 intracellular domain is not required for Stat3 activation (43), other Stat3 docking sites, apart from the IRTAM sequence and not necessarily containing tyrosine residues, may exist on the IFNaR1 intracellular domain. In addition, phosphatidylinositol 3Ј-kinase activation may also be regulated by insulin receptor substrate-1 (IRS-1) for which activation via Tyk2 and JAK1 has been described (54). Although association of MAP kinase (ERK2) with the IFNaR1 subunit has been reported (55), caution must be taken when linking this pathway to antiviral activity since inhibition of mitogen-activated protein/extracellular signal-regulated kinase kinase and mitogen-activated protein kinase activation had no effect on the antiviral activity of IFN␣ (56).…”

Fes Mediates the IL-4 Activation of Insulin Receptor Substrate-2 and Cellular Proliferation

“…IRS-1/2 can be recruited to Tyr-495 (Y1) of IL-4R␣ after IL-4 stimulation and is subsequently tyrosine phosphorylated (6). Although it has been reported that Jak1 is essential for the cytokine-mediated activation of IRS-1 in fibroblast cells (13)(14)(15), whether IRS is a direct substrate of Jak1 remains unclear.…”