POTENTIAL INTERACTION BETWEEN ANNEXIN-VI AND A 56-KDA PROTEIN-KINASE IN T-CELLS

Annexins belong to a large family of calcium-dependent phospholipid bi nding proteins known to undergo post-translational modifications such as phosphorylation. Physiological function of each annexin is still un clear since they may partipate in signal transduction. We have tested the presence of annexins in a T cell line (Jurkat) and studied their p hosphorylation by protein tyrosine kinases of the src family. Among an nexins I, II, V and VI found in Jurkat cells, annexin VI was shown to be phosphorylated in vitro by p56lck and annexins I and II by p60src. We could not detect the phosphorylation of A-VI in vivo, even after ce ll stimulation. However, a 56-kDa phosphoprotein was found to be assoc iated with A-VI after T cell activation. This 56-kDa protein shares so me characteristics with p56lck. (C) 1995 Academic Press, Inc.