Interleukin 1 induces specific phosphorylation of a 41 kDa plasma membrane protein from the human tumor cell line K 562.

An in vitro system was established to investigate the early effects of interleukin 1 (IL 1) on a clearly defined subcellular system, the plasma membrane. Murine IL 1 was obtained from the macrophage tumor line P 388 D1 and purified to apparent homogeneity. Plasma membranes from the human leukaemic tumor cell line K 562 were highly purified by differential ultracentrifugation. The monokine induced the specific phosphorylation of a 41 kDa plasma membrane protein. This could be demonstrated by incubating the plasma membranes in the presence of IL 1 and (gamma-32P)-ATP, separating the proteins by SDS-PAGE and subsequent autoradiography. A first biochemical reaction caused by IL 1 in the target organelle of the cell, the plasma membrane, was discovered, yielding a clue of how signal transmission may take place finally resulting in the stimulation of the responding cell.