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Comments on Attila Stetak et al. (2005) International Worm Meeting "Identification of PDZ- and FERM-domain proteins controlling the basolateral localization of LET-23 EGFR" (0)
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Attila Stetak, Peter Gutierrez, Erika Frohli-Hoier, & ALEX HAJNAL (2005). Identification of PDZ- and FERM-domain proteins controlling the basolateral localization of LET-23 EGFR presented in International Worm Meeting. Unpublished information; cite only with author permission.
The C.elegans hermaphrodite vulva is formed from the descendents of three out of six equipotent vulval precursor cells (VPCs, P3.p-P8.p). The gonadal anchor cell (AC) produces the LIN3 EGF growth factor that activates in P6.p the conserved EGFR/RAS/MAPK pathway to specify the primary cell fate. In order to receive the AC signal, the LET-23 EGFR must be kept on the basolateral surface of the VPCs facing the AC. The basolateral localization of LET-23 EGFR is essential for the efficient activation of RAS/MAPK signaling pathway and consequently for correct vulval induction. A ternary complex consisting of the PDZ domain proteins LIN-7, LIN-2 and LIN-10 is required for LET-23 EGFR localization to the basolateral compartment of the VPCs. Interestingly, PDZ domains are often found in adaptor proteins that regulate the subcellular localization of plasma membrane proteins. Furthermore, mammalian PDZ-domain proteins have been reported to bind to FERM (band 4.1/Ezrin/Radixin/Moesin)-proteins that link plasma membrane proteins to cytoskeletal structures. In order to find novel proteins that are necessary for the asymmetric localization of LET-23 EGFR, we downregulated by RNAi all predicted PDZ- (34 genes) and FERM-proteins (16 genes). The candidate genes were first tested in a let-60 ras(gf) background for a possible role in vulval induction. Only those genes that suppressed the let-60 ras(gf) multivulva phenotype were further analyzed for changes in LET-23 EGFR localization by immunostaining whole mounts. Four out of 6 genes that suppressed the let-60 ras(gf) phenotype displayed LET-23 EGFR localization defects (2 PDZ- and 2 FERM-domain proteins). RNAi against these four genes either caused apical mislocalization or intracellular accumulation of LET-23 EGFR in the VPCs. One FERM-domain gene appears to be required for the down-regulation of LET-23 EGFR in the 2<sym05> VPCs since RNAi knock-down resulted in persisting LET-23 EGFR expression in P5.p and P7.p. We are further characterizing these 4 candidates and their predicted binding partners to investigate their role in LET-23 EGFR localization.
Affiliation:
- Institute of Zoology, University of Zurich, Zurich, Switzerland