EFFECT OF EPIGALLOCATECHIN-3-GALLATE ON CALCIUM HOMEOSTASIS THROUGH INHIBITION OF THE PLASMA MEMBRANE CA2+-ATPASE

RINALDI, D.E; ONTIVEROS, M; MANGIALAVORI, I. .; ROSSI, ROLANDO; ROSSI, J.P.; FERREIRA GOMES, M

Buenos Aires

Congreso; REUNION CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

Sociedades de Biociencias

Catechins are polyphenols that possess beneficial properties for health, such as, antioxidant, anticancer, cardioprotective, neuroprotective and vasorelaxant properties. Epigallocatechin-3-gallate (EGCG), which is the major polyphenol component of green tea, is believed to be the compound most responsible for many of such properties. Different studies have shown that EGCG produces alterations in intracellular Ca2+ homeostasis which could be linked to alterations in the function of the mitochondria, different types of Ca2+ channels and calcium pumps. In this sense, the Plasma Membrane Ca2+-ATPase (PMCA) could be involved. PMCA transports Ca2+ actively to the extracellular medium coupled to the ATP hydrolysis maintaining the cellular homeostasis.The purpose of this work is to investigate the effect of EGCG on the PMCA and its relationship with the calcium homeostasis. We evaluated the effect of EGCG on the activity of PMCA purified from human red blood cells. EGCG showed a strong inhibition with an apparent affinity of 30 nM by increasing the phosphorylated intermediate which was found to be ADP sensitive. This suggest that EGCG could stabilize the E1P conformation on the reaction cycle of hydrolysis of ATP by PMCA. In addition, EGCG did not show to be competitive with Ca2+, but it increased the apparent affinity for Mg2+.In order to assess whether this inhibition may be of physiological relevance, we decided to characterize this effect in the context of a living cell by monitoring in real-time the changes in the cytosolic calcium levels. We tested the influence of EGCG on the activity of the PMCA transiently expressed in human embryonic kidney (HEK293) cells. We found that EGCG produced an increase of the cytoplasmic basal Ca2+ concentration and decreased the rate of removal of Ca2+ suggesting that PMCA activity was affected. These results suggest that the effect of the EGCG on intracellular Ca2+ levels may be linked to the inhibition of PMCA.