The mechanism of activation of PMCA by calmodulin or etanol involves dissociation of tubulin/PMCA complex.

MONESTEROLO, N; PREVITALI, G; CARLOS ANGEL ARCE; BARRA, H.S.; CASALE, C.H.

FEBS Journal

Año: 2008 vol. 275 p. 3567 - 3579

We showed recently that acetylated tubulin interacts with plasma membrane Na+,K+-ATPase and inhibits its enzyme activity in several types of cells. H+-ATPase of S. cerevisiae is similarly inhibited by interaction with acetylated tubulin. Activities of both these ATPases are restored upon dissociation of the acetylated tubulin/ATPase complex. We now report that in plasma membrane vesicles isolated from brain synaptosomes, another P-type ATPase, plasma membrane Ca2+-ATPase (PMCA), undergoes enzyme activity regulation by its association/dissociation with acetylated tubulin. Presence of acetylated tubulin/PMCA complex in membrane vesicles was demonstrated by analyzing the behaviour of acetylated tubulin in detergent partition, and by immunoprecipitation experiments. PMCA is known to be stimulated by ethanol and calmodulin at physiological concentrations. We found that treatment of plasma membrane vesicles with these reagents induced dissociation of the complex, with concomitant restoration of enzyme activity. Conversely, incubation of vesicles with exogenous tubulin induced association of acetylated tubulin with PMCA, and inhibition of enzyme activity. These findings indicate that the activation of synaptosomal PMCA by ethanol and calmodulin involves dissociation of the acetylated tubulin/PMCA complex. This regulatory mechanism was shown to also operate in living cells.