Transport of divalent cations mediated by the Plasma Membrane Calcium Pump

MALLKU ONTIVEROS; IRENE CECILIA MANGIALAVORI; JORGE MARTIARENA; SANDRA VERTRAETEN; JUAN PABLO F.C. ROSSI; MARIELA FERREIRA -GOMES

Bahía Blanca

Congreso; XLIII. Reunión Anual de la Sociedad Argentina de Biofísica; 2014

Sociedad Argentina de Biofísica

The plasma membrane calcium (PMCA) pump maintains the homeostasis in eukaryotic cells by transporting Ca2+ in a process coupled to the ATP hydrolysis. PMCA is activated by a Ca2+-calmodulin complex, by controlled proteolysis or by acidic phospholipids [1, 2]. The aim of this work was to investigate the effect and regulation of different divalent metal ions on PMCA activity. The experiments were performed with purified PMCA and inside-out vesicles from membranes of human erythrocytes. We evaluated the transport of Be2+, Sr2+, Ba2+, from the alkaline earth metals and Co2+, Cd2+ and Pb2+ from the fourth, fifth, and sixth periods, respectively. Results show that: (a) PMCA is able to transport Ca2+, Sr2+, Ba2+, Co2+ and Pb2+ with different Vmax and affinities, while Be2+ and Cd2+ are not transported; (b) activated PMCA showed an increasing to the apparent affinity for Ca2+, Sr2+ and Ba2+, however for Co2+ and Pb2+ the apparent affinity was not modified; (c) the closer the cation is to the Ca2+ radius, the transport is more efficient, at exception of Cd2+, which inhibits PMCA reacting with Cys residues. These results suggest that PMCA may contribute to the mechanism of toxicity/detoxification process under the eventual access of other divalent cations into the cell. With grants of ANPCYT, CONICET and UBACYT. 1- Mangialavori et al. J. Biol. Chem. 2009. 4823 2- Filomatori et al. J. Biol. Chem. 2003. 22265