CONICET | Buscador de Institutos y Recursos Humanos

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 preventing the dephosphorylation of the pump [1]. 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 lipids [2]. 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. Using small angle X-ray scattering (SAXS) we studied how the lipidic environment was changing alongside different molar fractions at different concentrations of aluminium. Further, with an aluminum-specific fluorescent probe (Lumogallion) we evaluate how free aluminium is modified by interacting with the different lipids.The inhibition of the pump by aluminium depends largely on the composition and concentration of phospholipids surrounding PMCA. SAXS measurements indicate that biophysical changes of the bilayer at different molar fractions could explain the difference in enzymatic activity. Moreover, we demonstrated how aluminium interacts with the micelles, in agreement with lumogallion fluorescence changes.