Inhibition of phosphatidylserine synthesis during Jurkat T cell activation

Abstract

Sodium ortho‐vanadate (Na 3 VO 4 ), an inhibitor of protein tyrosine phosphatase, induces a rapid (15 min) and strong inhibition of phosphatidylserine synthesis with an IC 50 = 100 µ m . The mode of action of Na 3 VO 4 was compared to that of CD3 mAbs. It was found that Na 3 VO 4 bypasses the major CD3‐induced T cell activation signals including protein tyrosine phosphorylation, p56lck activation and the generation of second messengers including inositol phosphates and its subsequent Ca 2+ mobilization as well as diacylglycerol production. These facts were confirmed by using a panel of Jurkat clones that differs by the expression of either tyrosine kinases involved in the CD3‐induced T cell activation pathway such as p56 lck , p72 syk and ZAP‐70 or some cell surface receptors such as the CD3/TCR complex or the CD45 phosphatase.