Natural flavonoids and calcium transport through biological membranes: molecular target and mechanisms of action

DEBORA RINALDI; MAXIMILIANO VIGIL; JUAN PABLO ROSSI; MALLKU ONTIVEROS; VICTORIA ESPELT; ROLANDO ROSSI; MARIEL MARDER; IRENE C MANGIALAVORI; MARIELA FERREIRA GOMES

Otro; Reunión Internacional ?Revisiting the Central Dogma of Molecular Biology at the Single Molecule Level; 2019

Latin American Federation of Biophysical Societies; Brazilian Biophysical Society

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 purified show that a quercetin-Mg2+ complex inhibited PMCA and it did not avoid the PMCA phosphorylation, resulting in an 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 model was 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 measured Ca2+ dynamics in different cell types. Results reveal that quercetin-Mg2+ treatment affected the cytoplasmic Ca2+ dynamics probably because the PMCA activity is inhibited. Experiments performed with human embryonic kidney cells, which transiently overexpress PMCA, show that the quercetin-Mg2+ treatment induced 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.