Plasma Membrane Calcium ATPase (PMCA) is modulated by aluminium thougth its effect on the lipids bilayer

MARILUNA DE SAUTU; JUAN PABLO ROSSI; MARIELA FERREIRA GOMES; IRENE MANGIALAVORI; GUSTAVO SCANAVACHI; ROSANGELA ITRI

Congreso; XLIV Congress of the Brazilian Biophysical Society; 2019

Aluminum (Al) is environmentally ubiquitous, providing human exposure and it has neurotoxic effects in humans and animals. The mechanisms that have been proposed to explain the toxicity of Al are linked to changes in the cellular calcium homeostasis. Recently, we demonstrated that Al inhibits the plasma membrane calcium ATPase activity by preventing the dephosphorylation of the pump [1]. PMCA is a P-ATPase involved in the regulation of the cell calcium homeostasis. Its function is to transport Ca2+ from cytoplasm towards the extracellular medium against the electrochemical gradient. PMCA like other integral membrane proteins operates surrounded by a complex and dynamic lipid bilayer, and the activity of this pump largely depends on the lipids [2]. In previous works, we showed that AlCl3 inhibits calcium efflux mediated by PMCA in HEK293T cells [3]. The aim of this work is to understand the effect that Al has on the lipid environment of the PMCA. This provide information of the distinctive effect that Al3+ would have depends on the lipidic composition of the cell membrane where the PMCA is located. To characterize this effect, mixed micelles of lipids and detergent (C12E10) were formed in different molar fractions and we measured how the PMCA activity varied and in presence of lipids. Then through SAXS experiments we studied how the lipidic environment was changing in the different molar fractions and in the presence of Al. With an aluminum-specific fluorescent probe (Lumogallion) we evaluate how free aluminum is modified by interacting with the different lipids.The inhibition of the pump by Al depends largely on the lipids surrounding it. The SAXS experiments results indicate that the biophysical changes in the different molar fractions could explain the difference in protein activity. Moreover, it was demonstrated how aluminum interacts with the micelles, coinciding with lumogallion fluorescence experiments. Acknowledgement: This work was supported by ANCYT PICT 2014 0065, CONICET PIP 0250 and Universidad de Buenos Aires 2014-2017: 20020130100254B, FAPESP, CNPQ and Universidade do Sao Paulo