The human T-cell leukemia/lymphotropic virus type 1 p12(I) protein binds the interleukin-2 receptor beta and gamma(c) chains and affects their expression on the cell surface

p12(I) is a small hydrophobic protein encoded by the human T-cell leukemia/lymphotropic virus type 1 (HTLV-1) that interacts with the I6-kDa component of the H+ vacuolar ATPase and cooperates with bovine papillomavirus 1 E5 oncoprotein in cell transformation. Just as an important step in E5 action appears to be its binding to the platelet-derived growth factor receptor, it was found that p12(I) binds specifically to both the beta and gamma(c) chains of the interleukin-2 receptor (IL-2R). The IL-2R beta and gamma(c) chains associated with p12(I) are endoglycosidase-H sensitive, suggesting that their interaction occurs in a pre-Golgi compartment. p12(I) stabilizes the immature forms of the IL-2R beta and gamma(c) chains and decreases their cell surface expression. The interactions of p12(I) with IL-2R beta and gamma(c) may have important implications in the immunosuppressive effect of HTLV-1 in vivo as well as in the ligand-independent HTLV-1-mediated T-cell proliferation.