Ligand-specific calcium mobilization in IL 2 and IL 3 dependent cell lines

Calcium mobilization is one of the earliest quantitative biochemical events associated with extracellular messenger stimulation of cellular proliferation. Therefore, purified recombinant lymphokines Interleukin 2 (IL 2) and Interleukin 3 (IL 3) were examined for ligand stimulation of calcium mobilization with highly specific interleukin-dependent cloned cell lines. Although IL 2 and IL 3 share neither amino acid structural homologies nor cellular tissue specificity, both recombinant polypeptides induced rapid influx of calcium into quiescent cells bearing specific receptors for the ligand. Neither ligand was capable of stimulating calcium mobilization in the non-homologous target cells which differed in tissue lineage. Stimulation of calcium mobilization demonstrated characteristic threshold dose-response kinetics and was observed under conditions where intracytoplasmic calcium levels were spontaneously depleted upon ligand deprivation. These data confirm that in addition to the activation of protein kinase C, growth regulatory polypeptides of mature T lymphocytes (IL 2) and hematopoietic stem cells (IL 3) share common biochemical features of the ligand-receptor signal transduction apparatus which initiates cellular proliferation.