title: An activating mutation in sos-1 identifies its Dbl domain as a critical inhibitor of the epidermal growth factor receptor pathway during Caenorhabditis elegans vulval development.
abstract: Proper regulation of receptor tyrosine kinase (RTK)-Ras-mitogen-activated protein kinase (MAPK) signaling pathways is critical for normal development and the prevention of cancer. SOS is a dual-function guanine nucleotide exchange factor (GEF) that catalyzes exchange on Ras and Rac. Although the physiologic role of SOS and its CDC25 domain in RTK-mediated Ras activation is well established, the in vivo function of its Dbl Rac GEF domain is less clear. We have identified a novel gain-of-function missense mutation in the Dbl domain of Caenorhabditis elegans SOS-1 that promotes epidermal growth factor receptor (EGFR) signaling in vivo. Our data indicate that a major developmental function of the Dbl domain is to inhibit EGF-dependent MAPK activation. The amount of inhibition conferred by the Dbl domain is equal to that of established trans-acting inhibitors of the EGFR pathway, including c-Cbl and RasGAP, and more than that of MAPK phosphatase. In conjunction with molecular modeling, our data suggest that the C. elegans mutation, as well as an equivalent mutation in human SOS1, activates the MAPK pathway by disrupting an autoinhibitory function of the Dbl domain on Ras activation. Our work suggests that functionally similar point mutations in humans could directly contribute to disease.
authors.affiliation: Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, 2000 Circle of Hope, Room 3242, Salt Lake City, UT 84112-5550, USA.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Modzelewska
authors.forename: Marc G
authors.initials: MG
authors.lastname: Elgort
authors.forename: Jingyu
authors.initials: J
authors.lastname: Huang
authors.forename: Gregg
authors.initials: G
authors.lastname: Jongeward
authors.forename: Amara
authors.initials: A
authors.lastname: Lauritzen
authors.forename: Charles H
authors.initials: CH
authors.lastname: Yoon
authors.forename: Paul W
authors.initials: PW
authors.lastname: Sternberg
authors.forename: Nadeem
authors.initials: N
authors.lastname: Moghal
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D020837:SOS1 Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology*; D048490:raf Kinases / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D020837:SOS1 Protein; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D048490:raf Kinases; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins