EVIDENCE FOR A NOVEL FUNCTION OF THE CD40 LIGAND AS A SIGNALING MOLECULE IN T-LYMPHOCYTES

The interaction of the CD40 receptor with its ligand has been shown to be crucial for the activation of B-lymphocytes. Here, me provide evid ence that the pg39 molecule/CD40 ligand (gp39/CD40L) also functions as a stimulatory molecule for T-lymphocytes. Activation of T-lymphocytes via gp39/CD40L induced a strong activation of Jun-N-terminal kinase ( JNK) and p38-K. Activation of these kinases correlates with a stimulat ion of Rad and inhibition of Rad prevents gp39/CD40L triggered JNK/p38 -K activation, Further, cellular stimulation via the CD40 ligand resul ts in tyrosine phosphorylation of cellular proteins and the activation of p56(lck), Inhibition of src-like kinases inhibits Rad as well as J NK/p38-K stimulation suggesting a signalling cascade from the gp39/CD4 0L via p56(lck) and Rad to JNK/p38-K. (C) 1997 Federation of European Biochemical Societies.