Tissue Distribution of the Four Gene Products of the Plasma Membrane Ca2+ Pump

Antibodies against the four isoforms of the human plasma membrane Ca(2+)-ATPase (PMCA) were raised using an N-terminal sequence of the pump as epitope. The antibodies against PMCA isoforms 1, 2, and 3 were not species-specific, e.g. they also recognized the corresponding proteins in rat, whereas that against the human PMCA isoform 4 failed to do so. The tissue distribution of the four isoforms was estimated by Western blot analysis. Two, PMCA1 and PMCA4, were expressed in all tissues tested (with the exception of the choroid plexus, where the former was not detected). In most tissues the signal from the PMCA1 protein exceeded that of PMCA4, the exception being the erythrocyte. The PMCA2 and PMCA3 proteins were only found in neuronal tissues; the PMCA2 protein was present in high concentrations in the cerebellum and in the cerebral cortex. At variance with previous results on mRNA (e.g. the kidney) no other tissues contained the PMCA2 protein. PMCA3 was the other tissue-specific isoform; in agreement with results in the rat, the protein was found in human neuronal tissues, particularly in the choroid plexus, but was practically absent in all other tissues tested.