Regulation of RAS oncogenicity by acetylation (original) (raw)
Related papers
Oncogene, 2000
Ras proteins are small GTPases playing a pivotal role in cell proliferation and dierentiation. Their activation state depends on the competing action of GTPase Activating Proteins (GAP) and Guanine nucleotide Exchange Factors (GEF). A tryptophan residue (Trp1056 in CDC25 Mm-GEF), conserved in all ras-speci®c GEFs identi®ed so far has been previously shown to be essential for GEF activity. Its substitution with glutamic acid results in a catalytically inactive mutant, which is able to eciently displace wild-type GEF from p21 ras and to originate a stable ras/GEF binary complex due to the reduced anity of the nucleotide-free ras/ GEF complex for the incoming nucleotide. We show here that this`ras-sequestering property' can be utilized to attenuate ras signal transduction pathways in mouse ®broblasts transformed by oncogenic ras. In fact overexpression of the dominant negative GEF W1056E in stable transfected cells strongly reduces intracellular ras´GTP levels in k-ras transformed ®broblasts. Accordingly, the transfected ®broblasts revert to wild-type phenotype on the basis of morphology, cell cycle and anchorage independent growth. The reversion of the transformed phenotype is accompanied by DNA endoreduplication. The possible use of dominant negative ras-speci®c GEFs as a tool to down-regulate tumor growth is discussed.
Ras superfamily GEFs and GAPs: validated and tractable targets for cancer therapy?
Nature Reviews Cancer, 2010
There is now considerable and increasing evidence for a causal role of aberrant activity of the Ras superfamily of small GTPases in human cancers. These GTPases act as GDP-GTP-regulated binary switches that control many fundamental cellular processes. A common mechanism of GTPase deregulation in cancer is the deregulated expression and/or activity of their regulatory proteins, guanine nucleotide exchange factors (GEFs) that promote formation of the active GTPbound state and GTPase activating proteins (GAPs) that return the GTPase to its GDP-bound inactive state. We assess the association of GEFs and GAPs with cancer and their druggability for cancer therapeutics.
Journal of Biological Chemistry, 1996
While Ras proteins are activated by stimulated GDP release, which enables acquisition of the active GTPbound state, little is known about how guanine nucleotide exchange factors (GEFs) interact with Ras to promote this exchange reaction. Here we report that mutations within the switch 2 domain of Ras (residues 62-69) inhibit activation of Ras by the mammalian GEFs, Sos1, and GRF/CDC25 Mm. While mutations in the 62-69 region blocked upstream activation of Ras, they did not disrupt Ras effector functions, including transcriptional activation and transformation of NIH 3T3 cells. Biochemical analysis indicated that the loss of GEF responsiveness of a Ras(69N) mutant was due to a loss of GEF binding, with no change in intrinsic nucleotide exchange activity. Furthermore, structural analysis of Ras(69N) using NMR spectroscopy indicated that mutation of residue 69 had a very localized effect on Ras structure that was limited to ␣-helix 2 of the switch 2 domain. Together, these results suggest that the switch 2 domain of Ras forms a direct interaction with GEFs.
Guanine nucleotide exchange factors: Activators of the Ras superfamily of proteins
BioEssays, 1995
Members of the Ras superfamily of proteins function as regulated GDP/GTP switches that cycle between active GTP-complexed and inactive GDP-complexed states. Guanine nucleotide exchange factors (GEFs) stimulate formation of the GTP-bound state, whereas GTPase activating proteins (GAPs) catalyze the formation of the GDP-bound state. We describe three studies that evaluate the mechanism of action of GEFs for Ras (SOS1 and RasGRF/ CDC25) or Ras-related Rho (Dbl and Vav) proteins. Growth factor-mediated activation of Ras is believed to be MEMBRANE TRANSLOCATION MECHANISM OF RAS GEF ACTIVATION? Quite a diverse collection of extracellular ligands can stimulate Ras by activating their cognate receptors (Satoh et al., 1992; Khosravi-Far and Der, 1994). All of these factors, including neurotransmitters, hormones, growth factors, and cytokines cause transient increases in Ras-GTP levels. In resting, unstimulated cells, the level of Ras-GTP is approximately 1-5% of the total Ras protein pool. Upon stimulation by extracellular
Differential Regulation of RasGAPs in Cancer
Genes & Cancer, 2011
Ever since their discovery as cellular counterparts of viral oncogenes more than 25 years ago, much progress has been made in understanding the complex networks of signal transduction pathways activated by oncogenic Ras mutations in human cancers. The activity of Ras is regulated by nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs), and much emphasis has been put into the biochemical and structural analysis of the Ras/GAP complex. The mechanisms by which GAPs catalyze Ras-GTP hydrolysis have been clarified and revealed that oncogenic Ras mutations confer resistance to GAPs and remain constitutively active. However, it is yet unclear how cells coordinate the large and divergent GAP protein family to promote Ras inactivation and ensure a certain biological response. Different domain arrangements in GAPs to create differential protein-protein and protein-lipid interactions are probably key factors determining the inactivation of the 3 Ras isoforms H-, K-, and N-Ras and their effector pathways. In recent years, in vitro as well as cell-and animal-based studies examining GAP activity, localization, interaction partners, and expression profiles have provided further insights into Ras inactivation and revealed characteristics of several GAPs to exert specific and distinct functions. This review aims to summarize knowledge on the cell biology of RasGAP proteins that potentially contributes to differential regulation of spatiotemporal Ras signaling.
Development of a Nucleotide Exchange Inhibitor That Impairs Ras Oncogenic Signaling
Chemistry - A European Journal, 2017
Despite more than three decades of intensee ffort, no anti-Ras therapies have reached clinical application. Contributing to this failureh as been an underestimation of Ras complexity andadearth of structural information.I nt his regard,r ecent studies have revealedt he highly dynamic character of the Ras surface and the existence of transient pocketss uitable for small-molecule binding,o pening up new possibilities for the development of Ras modulators. Herein,anovel Ras inhibitor (compound 12)i sd escribed that selectively impairsm utated Ras activity in ar eversible mannerw ithout significantly affecting wild-typeR as, reduces the Ras–guanosine triphosphate (GTP)l evels, inhibits the activation of the mitogen-activated protein kinase (MAPK) pathway,a nd exhibits remarkablec ytotoxic activity in Ras-drivenc ellular models. The use of molecular dynamics simu-lationsa nd NMR spectroscopye xperimentsh as enabled the molecular bases responsible for the interactions between compound 12 and Ras protein to be explored. The new Ras inhibitor binds partially to the GTP-binding region and extends into the adjacent hydrophobic pocket delimited by switchII. Hence, Ras inhibitor 12 could represent an ew compound for the developmento fm ore efficaciousd rugs to target Ras-driven cancers;acurrently unmet clinical need.
Guanosine Triphosphatase Stimulation of Oncogenic Ras Mutants
Proceedings of the …, 1999
Interest in the guanosine triphosphatase (GTPase) reaction of Ras as a molecular drug target stems from the observation that, in a large number of human tumors, Ras is characteristically mutated at codons 12 or 61, more rarely 13. Impaired GTPase activity, even in the ...
Journal of Biological Chemistry, 2000
Guanine nucleotide exchange factors (GEFs) are responsible for coupling cell surface receptors to Ras protein activation. Here we describe the characterization of a novel family of differentially expressed GEFs, identified by database sequence homology searching. These molecules share the core catalytic domain of other Ras family GEFs but lack the catalytic non-conserved (conserved non-catalytic/Ras exchange motif/structurally conserved region 0) domain that is believed to contribute to Sos1 integrity. In vitro binding and in vivo nucleotide exchange assays indicate that these GEFs specifically catalyze the GTP loading of the Ral GTPase when overexpressed in 293T cells. A central proline-rich motif associated with the Src homology (SH)2/SH3-containing adapter proteins Grb2 and Nck in vivo, whereas a pleckstrin homology (PH) domain was located at the GEF C terminus. We refer to these GEFs as RalGPS 1A, 1B, and 2 (Ral GEFs with PH domain and SH3 binding motif). The PH domain was required for in vivo GEF activity and could be functionally replaced by the Ki-Ras C terminus, suggesting a role in membrane targeting. In the absence of the PH domain RalGPS 1B cooperated with Grb2 to promote Ral activation, indicating that SH3 domain interaction also contributes to RalGPS regulation. In contrast to the Ral guanine nucleotide dissociation stimulator family of Ral GEFs, the RalGPS proteins do not possess a Ras-GTP-binding domain, suggesting that they are activated in a Ras-independent manner.