Plasma Membrane Calcium ATPase (PMCA) activity is modulated by aluminium due to its differential interaction with lipid bilayers

DE SAUTU, MARILINA; SCANAVACHI GUSTAVO; FERREIRA GOMES, MARIELA; ROSSI J. P. F. C.; ROSANGELA ITRI; MANGIALAVORI IRENE

Jornada; Biofísica en tiempos de COVID-19 : Primeras Jornadas Virtuales SAB 2020; 2020

Sociedad Argentina de Biofísica

PMCA is a P-ATPase involved in the regulation of the cell calcium homeostasistransporting Ca2+ from cytoplasm towards the extracellular medium. PMCA like otherintegral membrane proteins operates surrounded by a complex and dynamic lipidbilayer, and its activity largely depends on the lipids [1]. Aluminium (Al3+ and othersoluble species) is environmentally ubiquitous, providing human exposure andneurotoxic effects in humans and animals. The mechanisms proposed to explainaluminium toxicity are linked to changes in the cellular calcium homeostasis. In previousworks, we showed that AlCl3 inhibits calcium efflux mediated by PMCA in HEK293T cells.Also, we demonstrated that aluminium inhibits PMCA activity preventing thedephosphorylation of the pump [2].The aim of this work is to understand the effect of aluminium on the lipidic environmentof PMCA. Aluminium would have distinct effect depending on the lipid composition of thecell membrane where the PMCA is located. To characterize this effect, mixed micelles ofphospholipids and detergent (C12E10) were formed at different molar fractions and wemeasured how PMCA activity varied at different concentration of aluminium. Further, weevaluated other biophysical changes in the lipid bilayers performing Small Angle X-rayscattering (SAXS) experiments and we studied how the lipidic environment was changingalongside different molar fractions at different concentrations of aluminium. In turn, weevaluate changes in the membrane phase properties using the Laurdan probe.The results show a biphasic effect of activation and inhibition of the pump by aluminiumdepending largely on the composition and concentration of phospholipids surroundingPMCA. SAXS measurements indicate that biophysical changes of the bilayer at differentmolar fractions could explain the difference in enzymatic activity. Moreover, wedemonstrated how aluminium interacts with the lipids, in agreement with lumogallionfluorescence changes.[1] Pignataro, M. F et al (2015) Modulation of plasma membrane Ca2+-ATPase by neutralphospholipids: effect of the micelle-vesicle transition and the bilayer thickness. TheJournal of biological chemistry, 290(10), 6179?6190. doi:10.1074/jbc.M114. [2] De SautuM et al. BBA-Biomembrane (2018) 860(8):1580-1588. doi: 10.1016/j.bbamem.2018.05.014AcknowldegmentsThis work was supported by ANPCYT PICT 2014 0065, CONICET PIP 0250 and Universidad de BuenosAires: 20020130100254B, LNLS, CAPES, CNPq, FAPES