CONICET | Buscador de Institutos y Recursos Humanos

Research on flavonoids from plant sources has recently sparked increasing interest because of their beneficial health properties. Different studies have shown that flavonoids change the intracellular Ca2+ homeostasis linked to alterations in the function of mitochondria, Ca2+ channels and Ca2+ pumps. These findings hint at plasma membrane Ca2+-ATPase (PMCA) involvement, as it transports Ca2+ actively to the extracellular medium coupled to ATP hydrolysis, thus maintaining ion cellular homeostasis. The present study aims to investigate the effect of a flavonoid -quercetin- on PMCA both in isolated protein systems and in living cells,Results obtained using enzyme purifiedshow that a quercetin-Mg2+ complexinhibitedPMCA and itdid not avoid the PMCA phosphorylation, resulting inan increased level of phosphoenzyme in E1P conformation. On the other hand, we performed docking assays of quercetin-Mg2+as ligand and PMCA structure models as the receptor. PMCA modelwas obtained by homology modelling on Na,K-ATPase crystallographic structure.Then, we propose an interaction model between quercetin-Mg2+ complex and ATP binding domain in E1P conformation. To assess whether these quercetin-Mg2+ effects on PMCA purified could occur in living cells, we measuredCa2+ dynamics in different cell types. Results reveal that quercetin-Mg2+treatment affectedthe cytoplasmic Ca2+ dynamicsprobably because the PMCA activity is inhibited.Experiments performed withhuman embryonic kidney cells, which transiently overexpress PMCA, show that the quercetin-Mg2+treatmentinduced the PMCA inhibition, suggesting that the effects observed on isolated system could occur in a complex structure like a living cell.In conclusion, this work reveals a novel molecular mechanism through which quercetin-Mg2+ inhibit PMCA, which leads to Ca2+ homeostasis and signaling alterations in the cell.