Influence of CPZ and DMSO on the mechanism regulation of the plasma membrane Ca2+ ATPase of human erythrocyte

The calcium pumping ATPase of the erythrocyte plasma membrane (hPMCA4b) is the principal active system that expulse intracellular calcium into extracellular space in eukaryotic cells. PMCA is regulated by calmodulin (CaM), incrementing its ATP affinity. The use of molecules like chlorpromazine (CPZ) and dimethylsulfoxide (DMSO), inhibitors to hPMCA4b activity (non specific), were used in this study as a molecular tools that could help to understand the regulating mechanism of biochemical activation by CaM activation and their relationship with them. These molecules inhibit the PMCA activity, affecting its calcium homeostasis. CPZ is a phenotiazine that interfere with CaM functionality and it is commonly used in the treatment of mental disease. Erythrocytes membranes were used as the model biological system in order to assess the PMCA due to the absence of other calcium ATPases. PMCA activities in absence and presence of CaM and activated by trypsin exhibited inhibition by DMSO and CPZ. The ATPase activated with CaM in presence of CPZ does not interfere with the mechanism of regulation because there is no protection against the effect inhibitory of CPZ compared with the native PMCA. DMSO interacts with the regulation mechanism in the PMCA activated with CaM since there is the same profile of protection against the inhibition in comparison with the native enzyme. The recovery values of the activity in presence of CPZ and DMSO indicated the possible dilution of CPZ by the solvent. Supported by the grants of Fondos Mixtos CONACYT‐Edo. De Chihuahua and PROMEP‐CAEC.