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

Abstract

In the recent years, the toxicity of certain divalent cations has been associated with the alteration of intracellular Ca homeostasis. Among other mechanisms, these cations may affect the functionality of certain Ca-binding proteins and/or Ca pumps. The plasma membrane calcium pump (PMCA) maintains Ca 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 (Sr, Ba, Co, Cd, Pb or Be) could be transported by PMCA. Current results indicate that both purified and intact cell PMCA transported Sr with kinetic parameters close to those of Ca transport. The transport of Pb and Co by purified PMCA was, respectively, 50 and 75% lower than that of Ca, but only Co was extruded by intact cells and to a very low extent. In contrast, purified PMCA-but not intact cell PMCA-transported Ba at low rates and only when activated by limited proteolysis or by phosphatidylserine addition. Finally, purified PMCA did not transport Cd or Be, although minor Be transport was measured in intact cells. Moreover, Cd impaired the transport of Ca through various mechanisms, suggesting that PMCA may be a potential target of Cd-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.

Natural flavonoids inhibit the plasma membrane Ca2+-ATPase

“…To assess whether the effects of quercetin or gossypin observed on the purified hPMCA4 could occur in a living cell, the dynamics of cytoplasmic Ca 2+ ([Ca 2+ ] CYT ) were studied in HEK293T cells overexpressing hPMCA4 according to the method previously described [43,48]. The dynamics of [Ca 2+ ] CYT were examined by studying the alterations in [Ca 2+ ] CYT generated by Ca 2+ release from the ER, and by extracellular Ca 2+ entry through SOCs.…”

Epigallocatechin 3-gallate inhibits the plasma membrane Ca2+-ATPase: effects on calcium homeostasis

“…A calmodulin (CaM) affinity chromatography column was used to isolate PMCA from CaM-depleted human erythrocyte membranes [23]. Briefly, 0.5% C 12 E 10 -containing buffer was used to solubilize membrane proteins, they were centrifuged, and the supernatants were loaded into a CaM-Sepharose column with 1 mM Ca 2þ .…”

Cross-Talk between Mechanosensitive Ion Channels and Calcium Regulatory Proteins in Cardiovascular Health and Disease

“…The cell membrane controls the balance between intracellular and extracellular Ca 2+ via various proteins, and thus maintains Ca 2+ homeostasis. Plasma membrane Ca 2+ ATPase (PMCA), voltage-gated calcium channel (VGCC), Na + /Ca 2+ exchanger (NCX), and Orai have been identified as the main calcium regulatory proteins on the cell membrane [8][9][10][11]. Endoplasmic reticulum (ER) as an important Ca 2+ reservoir in the cell also contains some calcium regulatory proteins.…”