Search

Phosphorylation is one of the critical protein modifications, which can lead to changing the activity of the proteins and regulating a variety of biological processes. Therefore, it is essential to properly maintain the phosphorylation level on proteins by balancing the activity of kinases and phosphatases. In this study, we report that calcineurin, a serine/threonine phosphatase, counteracts with a salt inducible kinase (SIK) to control male tail development in Caenorhabditis elegans. The counteracting regulation is cell lineage-dependent; the number of defective rays from T lineage in animals lacking calcineurin tax-6 is decreased by knock-down of SIK kin-29. This result is in contrast with the knock-down of bone marrow protein (BMP) receptor kinase sma-6, which slightly aggravates the T lineage defect. Also, sma-6 knock-down results in modest defect in ray 1 of V5 lineage in the absence of tax-6 activity. Finally, knock-down of a tyrosine phosphatase cdc-25.3 does not affect the defective ray phenotype of calcineurin tax-6 loss-of-function(lf) mutants. Altogether, these results suggest that balanced phosphorylation mediated by tax-6 and kin-29 is required for proper development of T lineage rays, and tax-6 and sma-6 may function in a parallel pathway in the developmental process of V5 lineage ray 1. This study emphasizes the elaborated developmental process of male ray formation, in which carefully coordinated expression of various genes is essential. [ABSTRACT FROM AUTHOR]

Calcineurin (Cn) is a calcium/calmodulin-dependent serine/threonine protein phosphatase that has diverse functions in different cell types and organisms. We screened proteins interacting with the C. elegans CnA homolog, TAX-6, by the yeast two-hybrid system. CNP-3 (Calcineurin interacting protein-3) is a novel protein that physically interacts with the catalytic domain of TAX-6. It is strongly expressed in the nuclei of intestine, hypodermis, dorsal uterine regions and spermatheca. Expression begins around the 60-cell stage and proceeds during all larval stages and the adult. To elucidate the biological function of cnp-3 we isolated a cnp-3 deletion mutant. Since CNP-3 binds CnA, we looked at factors 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 had no gross defects compared to wild-type animal. However, the phenotypes of 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 serotoninmediated egg-laying defects than tax-6(p675) and cnb- 1(jh103), respectively. These results suggest that dysfunction of cnp-3 enhances certain calcineurin loss-offunction phenotypes in C. elegans. [ABSTRACT FROM AUTHOR]

Abstract: Calcineurin is a Ca2+/Calmodulin activated Ser/Thr phosphatase that is well conserved from yeast to human. In Caenorhabditis elegans, tax-6 and cnb-1 encode catalytic and regulatory subunits of calcineurin, respectively. We performed yeast two-hybrid screening using TAX-6 as a bait to identify calcineurin interacting proteins. KIN-29 is one of proteins that specifically interacted with TAX-6. KIN-29 is a Ser/Thr kinase previously shown to be involved in regulating gene expression of a subset of chemoreceptors in specific neurons. Both TAX-6 and KIN-29 are expressed in hypodermis, muscles, and neurons. Moreover, both calcineurin and kin-29 mutants exhibit similar phenotypes, namely small body size, small brood size, and slow growth. Here we describe specific genetic interaction between tax-6 and kin-29 in regulating body size, serotonin mediated egg laying, and chemoreceptor expression. [Copyright &y& Elsevier]

The enteric muscle contraction (EMC) is the last step of the defecation behavior which occurs every 50s in Caenorhabditis elegans. This EMC is regulated by intestinal and anal depressor muscles, which are innervated by GABA motor neurons. Our data show that calcineurin (tax-6) is expressed in intestinal muscle and anal depressor muscle, and the gain-of-function mutant of calcineurin, tax-6(jh107), shows defects in enteric muscle contractions. In addition, the intracellular region of EXP-1, an excitatory GABA receptor, specifically binds to calcineurin A. This interaction between TAX-6 and EXP-1 appears to be independent of both calcium and CNB, which is the calcium-binding regulatory subunit. Genetic evidence of epistasis between cnb-1(jh103) and exp-1(sa6) suggests that calcineurin functions as a negative regulator of excitatory GABA receptor in GABA signaling in C.elegans. [Copyright &y& Elsevier]

Ca2+/calmodulin-dependent calcineurin has been shown to have important roles in various Ca2+ signaling pathways. We have previously reported that cnb-1(jh103) mutants, null mutants of a regulatory B subunit, displayed pleiotropic defects including uncoordinated movement and delayed egg laying in Caenorhabditis elegans. Interestingly, gain-of-function mutants of a catalytic A subunit showed exactly opposite phenotypes to those of cnb-1(null) mutants providing an excellent genetic model to define calcium-mediated signaling pathway at the organism level. Furthermore, calcineurin is also important for normal cuticle formation, which is required for maintenance of normal body size in C.elegans. Genetic interactions between tax-6 and several mutants including egl-30 and egl-10, which are known to be involved in G-protein signaling pathways suggest that calcineurin indeed regulates locomotion and serotonin-mediated egg laying through goa-1(Goα) and egl-30(Gqα). Our results indicate that, along with CaMKII, calcineurin regulates G-protein-coupled phosphorylation signaling pathways in C.elegans. [Copyright &y& Elsevier]