Differences in the mechanisms of inhibition of aluminium on the plasma membrane and the sarcoplasmic reticulum calcium pumps

MARILINA DE SAUTU; NICOLAS ANDRÉS SAFFIOTI; MARIELA FERREIRA GOMES; DEBORA RINALDI; ROLANDO ROSSI; JUAN PABLO ROSSI; IRENE CECILIA MANGIALAVORI

Congreso; Reunión conjunta XLV Reunión Anual de la Sociedad Argentina de Biofísica (SAB) / III LAFeBS / X IberoAmerican Congress of Biophysics.; 2016

Aluminium (Al3+) is a metal widely distributed in the environment. Al3+ is involved with the pathophysiology of neurodegenerative disorders, such as Parkinsonism dementia and Alzheimer?s disease. Several mechanisms explain its neurotoxicity, for example, damage to the glycolytic metabolism, lipid peroxidation leading increased free radicals, protein modifications and changes in the cellular calcium homeostasis. The aim of this work was to study the molecular inhibitory mechanism of Al3+ on Ca2+-ATPases like the plasma membrane (PMCA) and the sarcoplasmic reticulum (SERCA). The function of these pumps is to reduce the cytoplasmic calcium concentration. For this purpose, we performed enzymatic measurements of the effect of Al3+ on purified preparations of PMCA and SERCA. Then, we measured the effect of different concentrations of Al3+ on intracellular calcium concentration in HEK293 cells using fluorescent probes. Our results show that: (1) Al3+ inhibits Ca2+-ATPase activity of both enzymes with similar apparent affinity; (2) In the presence of ATP, Al3+ dissociates SERCA, showing reversibility of the process. While in PMCA not occur. (3) In the presence of Al3+, the apparent affinity for Ca2+ of SERCA decreased, but not for PMCA; (3) Al3+ increases the phosphorylated intermediate (EP) of PMCA while it has not effect on SERCA; (5) Al3+ inhibits calcium efflux mediated by PMCA in HEK293 cells, suggesting that aluminum inhibits PMCA in vivo; (6) Preliminary studies using fluorescence microscopy and Lumogallion fluorescent probe, suggest that Al3+ could be located in the closeness of PMCA.This work propose for the first time a different inhibitory mechanism of action for Al3+ that involves intermediates of the ATP hydrolysis by these two Ca2+-transport ATPases.