The role of the lipid bilayer on the inhibition of the Plasma membrane calcium ATPase (PMCA) by aluminium

BELEN BIANCO; IRENE C MANGIALAVORI; MARILINA DE SAUTU; JUAN PABLO ROSSI; MARIELA FERREIRA -GOMES

Congreso; XLVIII Reunión Annual de la Sociedad de Biofísica Argentina.; 2019

PMCA is a P-ATPase involved in the regulation of the cell calcium homeostasis transporting Ca2+ from cytoplasm towards the extracellular medium. PMCA like other integral membrane proteins operates surrounded by a complex and dynamic lipid bilayer, and its activity largely depends on the type of lipids [1]. Aluminium (Al3+ and other soluble species) is environmentally ubiquitous, providing human exposure and neurotoxic effects in humans and animals. The mechanisms proposed to explain aluminium toxicity are linked to changes in the cellular calcium homeostasis. In previous works, we showed that AlCl3 inhibits calcium efflux mediated by PMCA in HEK293T cells. Also, we demonstrated that aluminium inhibits PMCA activity irreversibly by preventing the dephosphorylation of the pump [1]. The aim of this work is to understand the effect of aluminium on the lipidic environment of PMCA. Aluminium would have distinct effect depending on the lipid composition of the cell membrane where the PMCA is located. To characterize this effect, mixed micelles of phospholipids and detergent (C12E10) were formed at different molar fractions and we measured how PMCA activity varied with or without the presence of aluminium. Further, we characterize the interaction of aluminium in the same micelles with an aluminum-specific fluorescent probe (Lumogallion).Our results indicate that the inhibition of the pump by aluminium depends largely on the composition and concentration of phospholipids surrounding PMCA. Moreover, we show how aluminium interacts with the micelles, in agreement with lumogallion fluorescence changes. [1] Pignataro, M. F et al (2015) Modulation of plasma membrane Ca2+-ATPase by neutral phospholipids: effect of the micelle-vesicle transition and the bilayer thickness. The Journal of biological chemistry, 290(10), 6179?6190. doi:10.1074/jbc.M114. [2] De Sautu M et al. BBA-Biomembrane (2018) 860(8):1580-1588. doi: 10.1016/j.bbamem.2018.05.014 Acknowledgement: This work was supported by ANPCYT PICT 2017- 2615, CONICET PIP 0250 and Universidad de Buenos Aires: 20020130100254B.