Pleiotropic roles of calumenin (calu-1), a calcium-binding ER luminal protein, in Caenorhabditis elegans

Abstract 

Calumenin is a Ca²⁺ binding protein localizing at the lumen of the endoplasmic reticulum (ER). Although it has been implicated in various diseases, the in vivo functions of calumenin are largely unknown. Here, we report that calumenin has pleiotropic roles in muscle and cuticle function in Caenorhabditis elegans. Mutant analysis revealed that the calu-1 is required for regulating fertility, locomotion and body size. In addition, calu-1 is important for two behaviors, defecation and pharyngeal pumping, consistent with its ability to bind Ca²⁺. The genetic analysis further suggested the possibility that calu-1 regulates the pharyngeal pumping together with the inositol 1,4,5-triphosphate (IP₃) receptor encoded by itr-1. Taken together, our data suggest that calumenin is important for calcium signaling pathways in C. elegans.

Abbreviations: ER, endoplasmic reticulum, IPTG, isopropyl β-d-1-thiogalactopyranoside, SERCA, sarcoplasmic reticulum Ca²⁺-transporting ATPase, HIV, human immunodeficiency virus, pBoc, posterior body contraction, SEM, scanning electron microscopy, RNAi, RNA interference, IP₃, inositol 1,4,5-triphosphate, PDI, protein disulfide isomerase, PPIase, peptidyl prolyl cis–trans isomerase

Keywords: Ca²⁺ signaling, EF hand, Defecation, Pharyngeal pumping, Cuticle defect