Phosphorylation of a 15- to 17-kDa protein correlated with lytic function in cytotoxic T lymphocytes

CTL are activated to lyse their targets through the interaction of the CTL-R and the appropriate Ag on the surface of the target cell. Experiments with tumor-promoting phorbol esters have suggested that the activation and translocation of protein kinase C (PKC) to the CTL membrane may be important in the activation process. We have studied the functional role of PKC in lytic signal transduction by correlating the phosphorylation of a set of CTL membrane proteins bound by the lectin Con A with lytic function in CTL clones. The data obtained indicate that the phosphorylation of a 15- to 17-kDa polypeptide in this subset is associated with the translocation of PKC to the membrane and the stimulation of lytic function. This suggests that the 15- to 17-kDa protein may be a physiologically relevant substrate for PKC translocated to the membrane as a result of Ag-specific perturbation of the CTL-R.