Flavonoids and calcium transport through biological membranes.

ONTIVEROS, M; RINALDI, D.E; MARDER, M; ESPELT, M.V.; VIGIL, M.; MANGIALAVORI, I.; ROSSI, ROLANDO; ROSSI, J.P.; FERREIRA GOMES, M

La PLata

Congreso; XLVII Reunion Anual de la Sociedad Argentina de Biofisica; 2018

Recently, there has been increasing interest in the research on flavonoids from plant sources because of their beneficial properties for health. Several studies have attributed them anti-oxidative, anti-inflammatory, anti-mutagenic, and anti-carcinogenic properties coupled with their capacity to modulate key cellular enzyme functions. Flavonoids exert their effect in different ways, in particular, there are flavonoids related with changes of intracellular calcium concentration, suggesting that they could affect the Ca2+ transport. The present study seeks to investigate the effect of several natural flavonoids on hPMCA4 (human plasma membrane Ca2+-ATPase isoform 4), a P-type ATPase essential for the intracellular Ca2+ control in eukaryotic cells.Results obtained with purified PMCA showed that some flavonoids inhibited the PMCA activity and that the increase in the number of -OH in the B ring enhanced the inhibition potency. The best inhibitors were quercetin and gossypin with Ki of 0.3 and 4.1 M, respectively. The mechanism of inhibition of these flavonoids was dependent on the Mg2+ concentration, suggesting that the inhibitor is a flavonoid-Mg2+ complex. When phosphorylated intermediate (EP) was measured, quercetin led to the increase of EP, which was sensitive to ADP level, whereas gossypin induced a decrease. These results suggest that gossypin could affect the ATP binding whereas quercetin could prevent the conformational change E1P → E2P. To assess whether the effects of quercetin and gossypin on the purified hPMCA4 could occur in living cells, we evaluated the effect of these flavonoids monitoring changes in the cytoplasmic Ca2+ in HeK293T cells that overexpress hPMCA4. Results showed that quercetin and gossypin inhibited the PMCA activity. Fluorescence microscopy images indicate that both flavonoids distributed widely in the cytoplasm of cells, suggesting that it is possible a direct interaction between these flavonoids and the cytoplasmic domains of PMCA. Acknowledgement, with grants of CONICET, ANPCYT and UBACYT