Selectivity of plasma membrane calcium ATPase (PMCA)-mediated extrusion of toxic divalent cations in vitro and in cultured cells

FERREIRA-GOMES, MARIELA S.; MANGIALAVORI, IRENE C.; ONTIVEROS, MALLKU Q.; RINALDI, DEBORA E.; MARTIARENA, JORGE; VERSTRAETEN, SANDRA V.; ROSSI, JUAN PABLO F. C.

ARCHIVES OF TOXICOLOGY.

SPRINGER

Año: 2017

0340-5761

In the recent years, the toxicity of certain divalent cations has been associated with the alteration of intracellular Ca2+ homeostasis. Among other mechanisms, these cations may affect the functionality of certain Ca2+-binding proteins and/or Ca2+ pumps. The plasma membrane calcium pump (PMCA) maintains Ca2+ homeostasis in eukaryotic cells by mediating the efflux of this cation in a process coupled to ATP hydrolysis. The aim of this work was to investigate both in vitro and in cultured cells if other divalent cations (Sr2+, Ba2+, Co2+, Cd2+, Pb2+ or Be2+) could be transported by PMCA. Current results indicate that both purified and intact cell PMCA transported Sr2+ with kinetic parameters close to those of Ca2+ transport. The transport of Pb2+ and Co2+ by purified PMCA were, respectively, 50 and 75% lower than that of Ca2+ but only Co2+ was extruded by intact cells and to a very low extent. In contrast, purified PMCA ?but not intact cell PMCA? transported Ba2+ at low rates and only when activated by limited proteolysis or by phosphatidylserine addition. Finally, purified PMCA did not transport Cd2+ or Be2+, although minor Be2+ transport was measured in intact cells. Moreover, Cd2+ impaired the transport of Ca2+ through various mechanisms, suggesting that PMCA may be a potential target of Cd2+-mediated toxicity. The differential capacity of PMCA to transport these divalent cations may have a key role in their detoxification, limiting their noxious effects on cell homeostasis.