Nematode Sodium Calcium Exchangers: A Surprising Lack of Transport

Abstract

Na(+)/Ca(2+) exchangers are low-affinity, high-capacity transporters that rapidly transport calcium against a gradient of Na(+) ions. Na(+)/Ca(2+) exchangers are divided into three groups based upon substrate specificity: Na(+)/Ca(2+) exchangers (NCX), Na(+)/Ca(2+)/K(+) exchangers (NCKX), and Ca(2+)/cation exchangers (NCLX). In mammals, there are three NCX genes, five NCKX genes, and a single NCLX gene. The genome of the nematode Caenorhabditis elegans contains 10 Na(+)/Ca(2+) exchanger genes: three NCX, five NCLX, and two NCKX genes. In a previous study, we characterized the structural and taxonomic specializations within the family of Na(+)/Ca(2+) exchangers across the phylum Nematoda and observed a complex picture of Na(+)/Ca(2+) exchanger evolution across diverse nematode species. We noted multiple cases of putative gene gain and loss and, most surprisingly, did not detect members of the NCLX type of exchangers within subsets of nematode species. In this commentary, we discuss these findings and speculate on the functional outcomes and physiology of these observations. Our data highlight the importance of studying diverse systems in order to get a deeper understanding of the evolution and regulation of Ca(2+) signaling critical for animal function.

Keywords: NCLX; NCX; Nematode; evolution; sodium calcium exchanger.

Figure 1

Representative tree of the phylogenetic relationships between nematode species belonging to Clades I, III, IV, and V. Note: The types of sodium calcium exchangers are color coded red (NCKX), blue (NCX), and green (NCLX), and the number of colored lines represents the numbers of each exchanger detected from the genome of each nematode species in our analysis.