Flavonoids and calcium transport through biological membranes

ONTIVEROS, MALLKU Q.; ESPELT, MARÍA V.; ROSSI ROLANDO C; MARDER, MARIEL; MANGIALAVORI IRENE; FERREIRA GOMES, MARIELA; RINALDI, DEBORA E.; VIGIL MAXIMILIANO ANGEL; ROSSI JUAN PABLO

La Plata

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Biofísica; 2018

Sociedad Argentina de Biofísica

Recently, there has been increasing interest in the research on flavonoids fromplant sources because of their beneficial properties for health. Several studieshave attributed them anti-oxidative, anti-inflammatory, anti-mutagenic, and anticarcinogenic properties coupled with their capacity to modulate key cellularenzyme functions. Flavonoids exert their effect in different ways, in particular,there are flavonoids related to changes in intracellular calcium concentration,suggesting that they could affect the Ca2+ transport.The present study seeks to investigate the effect of several natural flavonoids onhPMCA4 (human plasma membrane Ca2+-ATPase isoform 4), a P-type ATPaseessential for the intracellular Ca2+ control in eukaryotic cells.Results obtained with purified PMCA showed that some flavonoids inhibited thePMCA activity and that the increase in the number of -OH in the B ring enhancedthe inhibition potency. The best inhibitors were quercetin and gossypin with Ki of0.3 and 4.1 mM, respectively. The mechanism of inhibition of these flavonoids wasdependent on the Mg2+ concentration, suggesting that the inhibitor is a flavonoidMg2+ complex. When phosphorylated intermediates ( EP) were measured,quercetin led to the increase of EP, which was sensitive to ADP, whereas gossypininduced a decrease. These results suggest that gossypin could affect the ATPbinding whereas quercetin could prevent the conformational change E1P → E2P.To assess whether the effects of quercetin and gossypin on the purified hPMCA4could occur in living cells, we monitored changes in the cytoplasmic Ca2+ inHeK293T cells that overexpress hPMCA4. Results are compatible with the idea thatquercetin and gossypin inhibited the PMCA activity. Fluorescence microscopyimages indicate that both flavonoids distributed widely in the cytoplasm of cells,suggesting that it is possible a direct interaction between these flavonoids and thecytoplasmic domains of PMCA.AcknowldegmentsWith grants of CONICET, ANPCYT and UBACYT