Biophysical Society Thematic Meeting| Lima 2019

Revisiting the Central Dogma of Molecular Biology at the Single-Molecule Level

Poster Abstracts

41-POS Board 41 NATURAL FLAVONOIDS AND CALCIUM TRANSPORT THROUGH BIOLOGICAL MEMBRANES: MOLECULAR TARGET AND MECHANISMS OF ACTION Mallku Ontiveros 1 ; Débora Rinaldi 1 ; Mariel Marder 1 ; Victoria Espelt 1 ; Maximiliano Vigil 1 ; Irene Mangialavori 1 ; Rolando Rossi 1 ; Juan Pablo Rossi 1 ; Mariela Ferreira-Gomes 1 ; 1 Instituto de Química y Fisicoquímica Biológica (IQUIFIB) UBA-CONICET, Química Biologica, Ciudad Autónoma de Buenos Aires, Argentina Recently, there has been increasing interest in research on flavonoids from plant sources because of their beneficial properties for health. Several studies have attributed them anti-oxidative and anti-carcinogenic properties. Flavonoids exert their effect in different ways, in particular, there are flavonoids related with changes of intracellular calcium concentration suggesting that they could disturb the calcium transport, including SERCA and PMCA. However, the molecular mechanisms underlying this effect are not yet clear. The present study seeks to investigate the effect of several natural flavonoids on hPMCA4 a P-type ATPase essential for the intracellular Ca 2+ control in eukaryotic cells. Results obtained with purified PMCA show that some flavonoids inhibited the PMCA activity related to the increase in the number of -OH in the B ring. The most potent inhibitors were quercetin and gossypin. The mechanism of inhibition of these flavonoids was dependent on the Mg 2+ concentration, suggesting that the real inhibitor is a flavonoid-Mg 2+ complex. When phosphorylated intermediates (EP) were measured, quercetin led to the increase of EP, which was sensitive to the ADP concentration in the medium, whereas gossypin induced a decrease. These results suggest that gossypin could affect the ATP binding site. We evaluated the effect of these flavonoids monitoring the changes in the cytoplasmic Ca 2+ in HeK293T and Caco-2 cells that overexpress hPMCA4. Fluorescence microscopy images indicate that both flavonoids distributed widely in the nucleus and the cytoplasm of cells. Results reveal that quercetin and gossypin are incorporated into the cells, showing that the cytoplasmic Ca 2+ dynamics is affected, probably because PMCA activity is inhibited when quercetin or gossypin pass into the cells. These findings suggest a direct interaction between PMCA cytoplasmic domains and these flavonoids. In conclusion, our results show that PMCA could be involved in the molecular mechanism underlying the flavonoids effects on biological systems.

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