Cell type-specific tyrosine phosphorylation of IL-2 receptor beta chain in response to IL-2.

Functional activities of the IL-2 receptor (IL-2R) beta chain exogenously expressed on lymphoid and non-lymphoid cells were examined in terms of phosphorylation of IL-2R beta and cell growth. Lymphoid MOLT-4 and its transfectants expressing IL-2R beta either alone or with IL-2R alpha chain were found to be rapidly phosphorylated predominantly at tyrosine residues of IL-2R beta and to be affected in their growth in an IL-2-dependent manner. In contrast, IL-2 induced neither phosphorylation of IL-2R beta nor cell growth in non-lymphoid transfectants derived from COS7, HeLa and L929, even though they acquired the IL-2 binding ability when coexpressed as IL-2R beta and IL-2R alpha. These results suggest that IL-2 induces activation of a tyrosine kinase possibly associated with IL-2R beta in a cell type-specific manner.