The plasma membrane calcium ATPase MCA-3 is required for clathrin-mediated endocytosis in scavenger cells of Caenorhabditis elegans

Plasma membrane Ca2+ ATPases (PMCAs) maintain proper intracellular Ca2+ levels by extruding Ca2+ from the cytosol. PMCA genes and splice forms are expressed in tissue-specific patterns in vertebrates, suggesting that these isoforms may regulate specific biological processes. However, knockout mutants die as embryos or undergo cell death; thus, it is unclear whether other cell processes utilize PMCAs or whether these pumps are largely committed to the control of toxic levels of calcium. Here, we analyze the role of the PMCA gene, mca-3, in Caenorhabditis elegans. We report that partial loss-of-function mutations disrupt clathrin-mediated endocytosis in a class of scavenger cells called coelomocytes. Moreover, components of early endocytic machinery are mislocalized in mca-3 mutants, including phosphatidylinositol-4,5-bisphosphate, clathrin and the Eps15 homology (EH) domain protein RME-1. This defect in endocytosis in the coelomocytes can be reversed by lowering calcium. Together, these data support a function for PMCAs in the regulation of endocytosis in the C. elegans coelomocytes. In addition, they suggest that endocytosis can be blocked by high calcium levels.