Molecular cloning and localization of a PMCA P-type calcium ATPase from the coral Stylophora pistillata.

Plasma-membrane calcium pumps (PMCAs) are responsible for the expulsion of Ca(2+) from the cytosol of all eukaryotic cells and are one of the major transport systems involved in long-term regulation of resting intracellular Ca(2+) concentration. An important feature of stony corals, one of the major groups of calcifying animals, is the continuous export of large quantities of Ca(2+) for skeletogenesis. Here, we report the cloning and functional expression of the stpPMCA gene from the coral Stylophora pistillata, and whose features resemble those of the plasma-membrane Ca(2+)-ATPase family of mammalian cells. This is the first known example of a Ca(2+)-ATPase from the phylum Cnidaria, and thus, the most phylogenetically distant PMCA sequence in the animal kingdom described to date. We demonstrate that the localization of stpPMCA within calicoblastic cells is fully coherent with its role in calcification. We also show that the coral Ca(2+) pump is more closely related to vertebrate PMCAs than to Caenorhabditis elegans PMCAs. The cloning of evolutionarily conserved genes from cnidarian species repeatedly shows that these genes encode similar functional domains. Moreover, this high level of gene conservation further validates the use of cnidarian model systems for studying processes shared by Eumetazoans.