title: Src promotes GTPase activity of Ras via tyrosine 32 phosphorylation.
abstract: Mutations in Ras GTPase and various other components of the Ras signaling pathways are among the most common genetic alterations in human cancers and also have been identified in several familial developmental syndromes. Over the past few decades it has become clear that the activity or the oncogenic potential of Ras is dependent on the nonreceptor tyrosine kinase Src to promote the Ras/Raf/MAPK pathway essential for proliferation, differentiation, and survival of eukaryotic cells. However, no direct relationship between Ras and Src has been established. We show here that Src binds to and phosphorylates GTP-, but not GDP-, loaded Ras on a conserved Y32 residue within the switch I region in vitro and that in vivo, Ras-Y32 phosphorylation markedly reduces the binding to effector Raf and concomitantly increases binding to GTPase-activating proteins and the rate of GTP hydrolysis. These results suggest that, in the context of predetermined crystallographic structures, Ras-Y32 serves as an Src-dependent keystone regulatory residue that modulates Ras GTPase activity and ensures unidirectionality to the Ras GTPase cycle.
authors.affiliation: Departments of Laboratory Medicine and Pathobiology and Biochemistry, University of Toronto, Toronto, ON, Canada M5S1A8;
authors.forename: Severa
authors.initials: S
authors.lastname: Bunda
authors.affiliation: Departments of Laboratory Medicine and Pathobiology and.
authors.forename: Pardeep
authors.initials: P
authors.lastname: Heir
authors.affiliation: Princess Margaret Cancer Centre, Toronto, ON, Canada M5G1L7; and.
authors.forename: Tharan
authors.initials: T
authors.lastname: Srikumar
authors.affiliation: Departments of Laboratory Medicine and Pathobiology and.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Cook
authors.affiliation: Brain Tumour Research Centre, The Hospital for Sick Children, University Health Network, Toronto, ON, Canada M5G1L7.
authors.forename: Kelly
authors.initials: K
authors.lastname: Burrell
authors.affiliation: Departments of Laboratory Medicine and Pathobiology and Biochemistry, University of Toronto, Toronto, ON, Canada M5S1A8;
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Kano
authors.affiliation: Departments of Laboratory Medicine and Pathobiology and.
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Lee
authors.affiliation: Brain Tumour Research Centre, The Hospital for Sick Children, University Health Network, Toronto, ON, Canada M5G1L7.
authors.forename: Gelareh
authors.initials: G
authors.lastname: Zadeh
authors.affiliation: Princess Margaret Cancer Centre, Toronto, ON, Canada M5G1L7; and.
authors.forename: Brian
authors.initials: B
authors.lastname: Raught
authors.affiliation: Departments of Laboratory Medicine and Pathobiology and Biochemistry, University of Toronto, Toronto, ON, Canada M5S1A8; michael.ohh@utoronto.ca.
authors.forename: Michael
authors.initials: M
authors.lastname: Ohh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism*; D011485:Protein Binding; D048490:raf Kinases / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D020690:GTPase-Activating Proteins; D008565:Membrane Proteins; D050505:Mutant Proteins; D019000:Phosphotyrosine; D006160:Guanosine Triphosphate; D019061:src-Family Kinases; D048490:raf Kinases; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human