title: Extracellular domain determinants of LET-23 (EGF) receptor tyrosine kinase activity in Caenorhabditis elegans.
abstract: Negative regulation of ErbB/EGFR signalling pathways is important for normal development and the prevention of cancer. In a genetic screen to uncover mechanisms that negatively regulate ErbB signalling in Caenorhabditis elegans, we isolated a second-site mutation (sy621) that promotes the activity of a gain-of-function allele (sa62gf) of the let-23 (EGF) receptor tyrosine kinase. We show that activation by the sa62 mutation (C359Y) likely results from a break in the conserved disulphide-bonded eighth module at the junction of CR1 and L2. The sy621 mutation causes a G270E change in the third disulphide-bonded module of CR1, and causes no phenotype on its own, but cooperates with the sa62 mutation to promote receptor activity. Although both sa62 single- and double-mutant receptors can function in the absence of ligand, they can be further activated by ligand. Our results support the current model for ligand-induced dimerization based on the recent crystal structures of HER3 and the EGFR, and provide more evidence for the generation of distinctly activated ErbB family members through mutation.
authors.affiliation: Howard Hughes Medical Institute and Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA. nmoghal@caltech.edu
authors.forename: Nadeem
authors.initials: N
authors.lastname: Moghal
authors.forename: Paul W
authors.initials: PW
authors.lastname: Sternberg
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000201:enzymology* / Q000235:genetics; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism; D066246:ErbB Receptors / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005836:Genitalia, Female / Q000002:abnormalities; D009154:Mutation; D017434:Protein Structure, Tertiary
chemical_list: D029742:Caenorhabditis elegans Proteins; D066246:ErbB Receptors; C085873:let-23 protein, C elegans