Does tubulin regulate phospholipids asymmetry in the plasma membrane of mammalians cells?

MUHLBERGER T; BALACH M; CASALE C; CAMPETELLI AN

Mar del Plata

Congreso; Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2015

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

Phospholipids distributes asymmetrically in the plasma membrane in most cells. This asymmetry is kept by lipid flippases, P4-ATPases that transport Phosphatidylethanolamine and Phosphatidylserine (PS) from the extra to the intracellular leaflet, while scramblases breaks assimetry by scrambling phospholipids between the two layers. While PS exposition is an apoptotic signal in most mammalian cells and is a key event in erythrocytes and platelets during clot formation, PS in the inner leaflet regulates the recruitment of polarity factors and cytoskeletal components. Erythrocytes from hypertensive patients have increased tubulin in the plasma membrane, what results in intracellular Na+ accumulation (because tubulin inhibit de Na+/K+ pump) and gives less deformable erythrocytes, one of the causes of arterial hypertension. Little is known about flippases regulation. We have showed previously that tubulin regulates several P-ATPases, so the aim of this work was to investigate a putative regulation of flippases by tubulin. Here, we developed a method to assay flippase activity in vitro. Our results show that tubulin inhibits flippase activity in vitro. In COS cells treated with carbachol, a muscarinic agonist that induces tubulin association to the plasma membrane, the flippase activity was decreased. Similarly, microtubules depolimerization by Nocodazole, reduces the flippase activity. These results suggest that tubulin would regulate the flippase activity in these cells and propose tubulin as one of the first described flippase regulators.