Effects of mono-ADP-ribosylation on cytoskeletal actin in chromaffin cellsand their release of catecholamine

To better understand the physiological role of mono-ADP-ribosylation in ani mals, we examined its role in chromaffin cells, Monoclonal antibodies again st rat brain ADP-ribosylhydrolase were prepared, one of which (9E7) complet ely inhibited the enzyme's activity with ADP-ribosylated actin as the subst rate. After actin monomers were polymerized by the addition of Mg2+, mono-A DP-ribosylation induced actin depolymerization. After mono-ADP-ribosylation , the actin monomers did not polymerize by the addition of Mg2+. Polymerize d actin cosedimented with chromaffin granules but mono-ADP-ribosylated acti n did not. After ADP-ribosylhydrolase on the membrane of chromaffin granule s was incubated with 9E7, mono-ADP-ribosylated actin did not cosediment wit h chromaffin granules. when chromaffin cells permeabilized with saponin wer e incubated with NAD and 9E7, actin and rho protein was mono-ADP-ribosylate d and stimulated catecholamine release from the cells. In histochemical exp eriments, catecholamine and actin filaments disappeared when the permeabili zed chromaffin cells were treated with NAD and 9E7. These findings indicate that mono-ADP-ribosylation breaks the actin barrier in order to move granu les during exocytosis, and ADP-ribosylactin hydrolase may keep the granules within the actin barrier. (C) 1999 Elsevier Science Ltd. All rights reserv ed.