Inhibition of SERCA and PMCA Ca-ATPase activities by polyoxotungstates.

Plasma membrane calcium ATPases (PMCA) and sarco(endo) reticulum calcium ATPases (SERCA) are key proteins in the maintenance of calcium homeostasis. Herein, we compare for the first time the inhibition of SERCA and PMCA calcium pumps by several polyoxotungstates (POTs), namely by Wells-Dawson phosphotungstate anions [PWO] (intact, {PW}), [PWO] (monolacunary, {PW}), [PWO] (trilacunary, {PW}), [HPWO] (hexalacunary, {PW}), [HPWVO] (trivanadium-substituted, {PWV}) and by Preyssler-type anion [NaPWO] ({PW}). The speciation in the solutions of tested POTs was investigated by P and V NMR spectroscopy. The tested POTs inhibited SERCA Ca-ATPase activity, whereby the Preyssler POT showed the strongest effect, with an IC value of 0.37 μM. For {PW} and {PWV} higher IC values were determined: 0.72 and 0.95 μM, respectively. The studied POTs showed to be more potent inhibitors of PMCA Ca-ATPase activity, with lower IC values for {PW}, {PW} and {PWV}.