title: Feedback regulation of Ras signaling by Rabex-5-mediated ubiquitination.
abstract: Ras proteins play a central role in transducing signals that control cell proliferation, differentiation, motility, and survival. The location-specific signaling activity of Ras has been previously shown to be regulated by ubiquitination [1]. However, the molecular machinery that controls Ras ubiquitination has not been defined. Here we demonstrate through biochemical and functional analyses that Rabex-5 (also known as RabGEF1) [2, 3] functions as an E3 ligase for Ras. Rabex-5-mediated Ras ubiquitination promotes Ras endosomal localization and leads to the suppression of ERK activation. Moreover, the Ras effector RIN1 [4, 5] is required for Rabex-5-dependent Ras ubiquitination, suggesting a feedback mechanism by which Ras activation can be coupled to ubiquitination. These findings define new elements in the regulatory circuitry that link Ras compartmentalization to signaling output.
authors.affiliation: Department of Biochemistry, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Lizhong
authors.initials: L
authors.lastname: Xu
authors.forename: Veronica
authors.initials: V
authors.lastname: Lubkov
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Taylor
authors.forename: Dafna
authors.initials: D
authors.lastname: Bar-Sagi
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D011992:Endosomes / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D025461:Feedback, Physiological; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D047908:Intracellular Signaling Peptides and Proteins; C108382:RABGEF1 protein, human; C092117:RIN1 protein, human; D044767:Ubiquitin-Protein Ligases; D048049:Extracellular Signal-Regulated MAP Kinases; D018631:ras Proteins