CNP-3, a novel calcineurin Interacting Protein-3, genetically modulates calcineurin deficient phenotypes in Caenorhabditis elegans

Abstract

Calcineurin (Cn) is a calcium/calmodulin-dependent serine/threonine protein phosphatase which exerts diverse functions in different cell types and organisms. We screened the proteins interacting with C. elegans CnA homolog, TAX-6 by yeast two-hybrid system. CNP-3 is one of the novel proteins that physically interacted with the catalytic domain of TAX-6. The cnp-3 is strongly expressed in the nuclei of intestine, hypodermis, dorsal uterine regions and spermatheca. The expression begins around 60-cell stage and progresses all larval stages and adult. To elucidate the biological function of the cnp-3 in C. elegans, we isolated cnp-3 deletion mutant. Since the cnp-3 is a binding partner of calcineurin A (CnA), we specifically examined the phenotypic abnormalities associated with calcineurin loss-of-function mutants, such as brood size, body size, serotonin- and levamisole-mediated egg-laying behavior. The cnp-3(jh145) single mutant showed no gross defect compared to wild-type animal. However, the double mutants, tax-6(p675);cnp-3(jh145) and cnb-1(jh103);cnp-3(jh145), were more severe in terms of brood size, body size and serotonin-mediated egg-laying defects compared to tax-6(p675) and cnb-1(jh103), respectively. These results suggest that the dysfunction of the cnp-3 enhances the calcineurin loss-of-function mutant phenotypes and thus, the cnp-3 genetically interacts with calcineurin