title: Cullin 5 destabilizes Cas to inhibit Src-dependent cell transformation.
abstract: Phosphorylation-dependent protein ubiquitylation and degradation provides an irreversible mechanism to terminate protein kinase signaling. Here, we report that mammary epithelial cells require cullin-5-RING-E3-ubiquitin-ligase complexes (Cul5-CRLs) to prevent transformation by a Src-Cas signaling pathway. Removal of Cul5 stimulates growth-factor-independent growth and migration, membrane dynamics and colony dysmorphogenesis, which are all dependent on the endogenous tyrosine kinase Src. Src is activated in Cul5-deficient cells, but Src activation alone is not sufficient to cause transformation. We found that Cul5 and Src together stimulate degradation of the Src substrate p130Cas (Crk-associated substrate). Phosphorylation stimulates Cas binding to the Cul5-CRL adaptor protein SOCS6 and consequent proteasome-dependent degradation. Cas is necessary for the transformation of Cul5-deficient cells. Either knockdown of SOCS6 or use of a degradation-resistant Cas mutant stimulates membrane ruffling, but not other aspects of transformation. Our results show that endogenous Cul5 suppresses epithelial cell transformation by several pathways, including inhibition of Src-Cas-induced ruffling through SOCS6.
authors.affiliation: Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, Seattle, WA 98109, USA.
authors.forename: Anjali
authors.initials: A
authors.lastname: Teckchandani
authors.forename: George S
authors.initials: GS
authors.lastname: Laszlo
authors.forename: Sergi
authors.initials: S
authors.lastname: Simó
authors.forename: Khyati
authors.initials: K
authors.lastname: Shah
authors.forename: Carissa
authors.initials: C
authors.lastname: Pilling
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Strait
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Cooper
mesh_terms: D000818:Animals; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D050719:Crk-Associated Substrate Protein / Q000378:metabolism*; D044842:Cullin Proteins / Q000235:genetics* / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D055785:Gene Knockdown Techniques; D051379:Mice; D015398:Signal Transduction / Q000235:genetics; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D050719:Crk-Associated Substrate Protein; D044842:Cullin Proteins; C473086:Socs6 protein, mouse; D050826:Suppressor of Cytokine Signaling Proteins; C531145:cullin5 protein, mouse; D019061:src-Family Kinases
keywords: Cas; Cul5; Cullin 5; Migration; Src; Transformation; Ubiquitin