Natural flavonoids and calcium transport through biological membranes

HOLZWARTH CELESTE; PAKCIARZ PABLO; TOMISAKI, MARINA; RINALDI, DEBORA; ROSSI JPFC; MANGIALAVORI IRENE; FERREIRA GOMES, MARIELA; ONTIVEROS, MALLKU

Buenos Aires

Simposio; FRONTIERS IN BIOSCIENCE 4; 2023

Flavonoids are polyphenolic compounds synthesized and widely distributed in plants.Numerous studies have reported on the antioxidative, anti-inflammatory and anti-carcinogenic properties of flavonoids, along with their ability to modulate essentialcellular enzyme functions. Some flavonoids have been found to be associated withchanges in intracellular Ca 2+ concentration, which could be linked to their impact onCa 2+ transport systems. Several studies suggest that certain flavonoids inhibit a varietyof P-ATPases, such as the sarcoplasmic/endoplasmic reticulum and the plasmamembrane Ca 2+ -ATPases (PMCA). However, the molecular mechanism of this effect isnot yet defined. PMCA is a P-ATPase regulated by calmodulin (CaM) that maintainsthe homeostasis of intracellular Ca 2+ in eukaryotic cells, coupling the transport of Ca 2+with ATP hydrolysis.The aim of this work is to characterize the effect of quercetin, a flavonol aglycone, onPMCA both in the purified system and in living cells.The studies performed on HeK293T cells treated with quercetin indicate that it iscapable of entering the cells and staying in the cytoplasm for at least 30 minutes.Additionally, measurements of cytoplasmic calcium levels suggest that the systemsresponsible for the expulsion of cytoplasmic calcium are affected in the presence ofquercetin.Results obtained with purified PMCA show that quercetin inhibited PMCA activitythrough a Mg 2+ complex (Mg-quercetin) with a Ki of 0.05 M. This inhibition wasindependent of lipid environment of protein suggesting that Mg-quercetin interactsdirectly with PMCA. Additionally, quercetin inhibited the activity of CaM-activatedPMCA, indicating that it interacts with the enzyme bound to CaM. This evidence issignificant because CaM activates PMCA when the Ca 2+ concentration in the cytoplasmincreases, implying that quercetin could inhibit the pump in living cells.In conclusion, this study provides evidence that can explain the molecular basis of theeffects of flavonoids on calcium homeostasis in cells.Acknowledgement, with grants of CONICET, ANPCYT and UBACYT