Mechanism of inhibition of Epigallocatechin on the Plasma Membrane Ca2+-ATPase

ANA RIESCO; DEBORA RINALDI; MARIELA FERREIRA GOMES; MARIEL MARDER; JUAN PABLO ROSSI; IRENE MANGIALAVORI

Congreso; LII Reunión Anual de la Sociedad Argentina de Investigaciones Bioquímicas; 2016

Epigallocatechin 3-gallate (EGCg) is the major polyphenol component and primarily responsible for the green tea effects. EGCg beneficial effects include mainly antioxidant, anti-inflammatory and neuroprotective effects. However, EGCg has been suggested to inhibit the activity of the Na+,K+-ATPase, a P-type ATPase that is primarily responsible for maintaining the osmotic balance within animal cells. In order to investigate whether EGCG inhibits other members of the P-type ATPase we evaluated the effect of EGCg on the Plasma membrane Ca2+-ATPase (PMCA). PMCA transports Ca2+ actively to the extracellular medium coupled to the ATP hydrolysis maintaining the cellular homeostasis.We performed enzymatic measurements on purified preparations of PMCA obtained from human red blood cells and on HEK293T cells where we evaluated the Ca2+ flux as a measured to (of?) PMCA activity.Results show that EGCg is a potent inhibitor of PMCA with a K0.5 of (0.032 ± 0.003) M and that the inhibition would occur by a decrease of the rate of the E1P to E2P transition of phosphorylated intermediate in the catalytic cycle of the PMCA. Moreover, measurements of Ca2+ flux in HEK293T cells show that EGCg decreased the rate of removal of Ca2+ with respect to the control, suggesting that those systems that remove calcium including PMCA would be affected.