Regulated Disruption of Inositol 1,4,5-Trisphosphate Signaling inCaenorhabditis elegansReveals New Functions in Feeding and Embryogenesis

Abstract

Inositol 1,4,5-trisphosphate (IP₃) is an important second messenger in animal cells and is central to a wide range of cellular responses. The major intracellular activity of IP₃is to regulate release of Ca²⁺from intracellular stores through IP₃receptors (IP₃Rs). We describe a system for the transient disruption of IP₃signaling in the model organismCaenorhabditis elegans. The IP₃binding domain of the C. elegans IP₃R, ITR-1, was expressed from heat shock-induced promoters in live animals. This results in a dominant-negative effect caused by the overexpressed IP₃binding domain acting as an IP₃“sponge.” Disruption of IP₃signaling resulted in disrupted defecation, a phenotype predicted by previous genetic studies. This approach also identified two new IP₃-mediated processes. First, the up-regulation of pharyngeal pumping in response to food is dependent on IP₃signaling. RNA-mediated interference studies and analysis of itr-1mutants show that this process is also IP₃R dependent. Second, the tissue-specific expression of the dominant-negative construct enabled us to circumvent the sterility associated with loss of IP₃signaling through the IP₃R and thus determine that IP₃-mediated signaling is required for multiple steps in embryogenesis, including cytokinesis and gastrulation.