Activation of phospholipase D following perturbation of the human T lymphocyte antigen receptor/CD3 complex is dependent upon protein kinase C.

Perturbation of the T lymphocyte antigen receptor/CD3 complex or phorbol ester stimulation leads to activation of phospholipase D in the Jurkat T lymphocyte cell line. These observations suggested that phospholipase D activation might result from activation of protein kinase C. In other systems, phospholipase D activity has been shown to be under G-protein or protein kinase C control. Studies detailed here demonstrate that commonly used inhibitors of protein kinase C had unrelated, diverse effects on phospholipase D activity in T lymphocytes. However, protein kinase C down-regulation resulting from prolonged cellular exposure to phorbol esters led to abrogation of anti-CD3-stimulated phospholipase D activation. The results presented underline the complexity of studies employing inhibitors of protein kinase C, suggest interesting approaches to isolation of phospholipase D dependent signalling pathways, confirm that T cell antigen receptor-linked activation of phospholipase D is dependent upon protein kinase C activity and suggest that distant events of T lymphocyte activation are dependent upon the establishment of a positive feedback loop involving protein kinase C and phospholipase D which would result in the prolonged activation of protein kinase C required for certain lymphokine production.