INOSITOL TRISPHOSPHATE MEDIATES A RAS-INDEPENDENT RESPONSE TO LET-23 RECEPTOR TYROSINE KINASE ACTIVATION IN C-ELEGANS

Activity of LET-23, the C. elegans homolog of the epidermal growth fac tor receptor, is required in multiple tissues. RAS activation is neces sary and sufficient for certain LET-23 functions. We show that an inos itol trisphosphate receptor can act as a PAS-independent, tissue-speci fic positive effector of LET-23. Moreover, an inositol trisphosphate k inase negatively regulates this transduction pathway. Signals transduc ed by LET-23 control ovulation through changes in spermathecal dilatio n, possibly dependent upon calcium release regulated by both IP3 and I P4. Our results demonstrate that one mechanism by which receptor tyros ine kinases can evoke tissue-specific responses is through activation of distinct signal transduction cascades in different tissues.