Phosphorylation of p56lck by external ATP in intact cells

Abstract Recent studies have suggested a role for extracellular ATP. In this report we show that extracellular labelled ATP crosses the plasma membrane of intact lymphoma cells and peripheral blood lymphocytes and phosphorylates p56 lck a tyrosine protein kinase specific of lymphoid cells. Two other phosphoproteins of 92Kd and 35Kd become detectable on alcali treated gels. Phosphorylation occurs within minutes following addition of ATP. ATP, GTP, ADP and an ATP analog prevent phosphorylation but not AMP nor P j ; trypsinization of cells abolishes labelling. The possible involvement of P 2 Purinergic receptors is discussed.