Differential inhibition of Plasma Membrane Ca2+-ATPase by quercetin and gossypin

GENTILE, L. ; RINALDI, D.; MANGIALAVORI, I.; MARDER, M.; ROSSI, JP; FERREIRA-GOMES, M.

Córdoba

Congreso; LII Reunión de SAIB; 2016

Flavonoids are commonly found in fruit and vegetables and they are also part of human diet. These compounds are also believed to have cancer chemoprotective properties by triggering apoptosis via the Ca2+-dependent mitochondrial pathway which can be activated through an increase of cytosolic [Ca2+] ([Ca2+]c) involving the inhibition of sarcoplasmic/endoplasmic reticulum Ca2+ ATPase and plasma membrane calcium ATPase (PMCA). The aim of this work is to characterize the inhibition of PMCA by quercetin and gossypin, two flavonoids with known anticarcinogenic activity. The differences in the mechanism of inhibition will be analyzed considering these compound?s molecular structures, as quercetin is a flavonol aglycone and gossypin is a flavonol glycoside, and their possible interaction with the pump. We evaluated the [Ca2+]c in HEK293T cells and also studied the Ca2+-ATPase activity in purified PMCA obtained from human erythrocytes. The results showed that (1) PMCA activity was inhibited by quercetin and gossypin with a K0.5 of 0.34 ± 0.01 and 5.1 ± 1 M, respectively; (2) PMCA phosphorylation showed that quercetin led to the accumulation of phosphoenzyme while gossypin induced a decrease; (3) quercetin produced a larger calmodulin PMCA inhibition than gossypin; (4) in HEK293T cells, quercetin and gossypin lowered Ca2+ removal rate compared to control. These results show that quercetin and gossypin inhibit PMCA by different mechanisms, possibly due to their distinct molecular structures, giving rise to the idea that PMCA could be a novel target for flavonoids.