CD39 as a caveolar-associated ectonucleotidase

CD39 is a human lymphoid cell activation antigen, (also referred to E-ATPDa se or apyrase) that hydrolyzes extracellular ATP and ADP, Although it has b een widely studied, its physiological role, however, still remains unclear, This ectonucleotidase generally is said to be evenly distributed in the me mbrane of the cells. However, we observed that in cell types which possess caveolae, specialised membrane invaginations involved in signalling, CD39 i s preferentially targeted to these membrane microdomains. Since all molecul es involved in signalling (eNOS, G-proteins, receptors) which are targeted to the caveolae undergo posttranslational modifications (e.g., palmitoylati on) we hypothesize the same to be the case for CD39. Furthermore, its prese nce in the caveolae supports its participation in signalling events. (C) 19 99 Academic Press.