Association of Src-Related Kinase Lyn with the Interleukin-2 Receptor and Its Role in Maintaining Constitutive Phosphorylation of JAK/STAT in Human T-Cell Leukemia Virus Type 1-Transformed T Cells

Human T-cell leukemia virus type 1 (HTLV-1) infection and transformation are associated with an incremental switch in the expression of the Src-related protein tyrosine kinases Lck and Lyn. We examined the physical and functional interactions of Lyn with receptors and signal transduction proteins in HTLV-1-infected T cells. Lyn coimmunoprecipitates with the interleukin-2 beta receptor (IL-2Rβ) and JAK3 proteins; however, the association of Lyn with the IL-2Rβ and Lyn kinase activity was independent of IL-2 stimulation. Phosphorylation of Janus kinase 3 (JAK3) and signal transducers and activator of transcription 5 (STAT5) proteins was reduced by treatment of cells with the Src kinase inhibitor PP2 or by ectopic expression of a dominant negative Lyn kinase protein.