The epidermal growth factor system in Caenorhabditis elegans

Abstract

The single known epidermal growth factor-like growth factor and single epidermal growth factor receptor in Caenorhabditis elegans mediate two types of processes, each via a distinct signal transduction pathway. This pathway is subject to multiple redundantly acting positive and negative modulatory signals and, in addition, virtually, every step of signaling from receptor localization to communication to RNA Pol II is regulated in a precise manner. Several instances of cell fate specification during organogenesis require the RAS–MAP kinase pathway, as well as multiple nuclear factors. In contrast, appropriate myoepithelial contractions during ovulation involve IP3-mediated signal transduction. Positive modulators of the RAS pathway include KSR, SUR-8, phosphatase PP2A, and a zinc cation diffusion facilitator. Negative regulators of the RAS pathway include homologs of CBL, GAP-1, ACK, and MAP kinase phosphatase, while negative regulators of the IP3 pathway are enzymes that modify IP3. In addition to its stimulation of RAS activity, the GRB2 homolog SEM-5 acts negatively on both signaling pathways, as does the Ack-related kinase ARK-1.

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