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

SAFFIOTI, NICOLÁS ANDRÉS; ROSSI ROLANDO; DE SAUTU, MARILINA; FERRIERA GOMES, MARIELA; RINALDI, DÉBORA; ROSSI JUAN PABLO; MANGIALAVORI, IRENE CECILIA

Tucumán

Congreso; III Latin American Federation of Biophysical Societies (LAFeBS) ? IX IberoAmerican Congress of Biophysics ? XLV Reunion Anual SAB 2016; 2016

Latin American Federation of Biophysical Societies (LAFeBS)

Differences and similarities in the mechanisms of inhibition ofaluminium on the plasma membrane and the sarcoplasmicreticulum calcium pumpsAluminium (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. Severalmechanisms explain its neurotoxicity, for example, damage to the glycolyticmetabolism, 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 mechanismof Al3+ on Ca2+-ATPases like the plasma membrane (PMCA) and thesarcoplasmic reticulum (SERCA). The function of these pumps is toreduce the cytoplasmic calcium concentration. For this purpose, weperformed enzymatic measurements of the effect of Al3+ on purifiedpreparations of PMCA and SERCA. Then, we measured the effect ofdifferent concentrations of Al3+ on intracellular calcium concentrationin HEK293 cells using fluorescent probes.Our results show that: (1) Al3+ inhibits Ca2+-ATPase activity of bothenzymes with similar apparent affinity; (2) In the presence of ATP,Al3+ dissociates SERCA, showing reversibility of the process. Whilein PMCA not occur. (3) In the presence of Al3+, the apparent affinityfor Ca2+ of SERCA decreased, but not for PMCA; (3) Al3+ increasesthe phosphorylated intermediate (EP) of PMCA while it has not effecton SERCA; (5) Al3+ inhibits calcium efflux mediated by PMCA inHEK293 cells, suggesting that aluminum inhibits PMCA in vivo; (6)Preliminary studies using fluorescence microscopy and Lumogallionfluorescent probe, suggest that Al3+ could be located in the closenessof PMCA.This work propose for the first time a different inhibitory mechanismof action for Al3+ that involves intermediates of the ATP hydrolysis bythese two Ca2+-transport ATPases.With grants of ANPCYT, CONICET, UBACYT