title: Inhibition of Ral GTPases Using a Stapled Peptide Approach.
abstract: Aberrant Ras signaling drives numerous cancers, and drugs to inhibit this are urgently required. This compelling clinical need combined with recent innovations in drug discovery including the advent of biologic therapeutic agents, has propelled Ras back to the forefront of targeting efforts. Activated Ras has proved extremely difficult to target directly, and the focus has moved to the main downstream Ras-signaling pathways. In particular, the Ras-Raf and Ras-PI3K pathways have provided conspicuous enzyme therapeutic targets that were more accessible to conventional drug-discovery strategies. The Ras-RalGEF-Ral pathway is a more difficult challenge for traditional medicinal development, and there have, therefore, been few inhibitors reported that disrupt this axis. We have used our structure of a Ral-effector complex as a basis for the design and characterization of α-helical-stapled peptides that bind selectively to active, GTP-bound Ral proteins and that compete with downstream effector proteins. The peptides have been thoroughly characterized biophysically. Crucially, the lead peptide enters cells and is biologically active, inhibiting isoform-specific RalB-driven cellular processes. This, therefore, provides a starting point for therapeutic inhibition of the Ras-RalGEF-Ral pathway.
authors.affiliation: From the Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom, Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom.
authors.forename: Jemima C
authors.initials: JC
authors.lastname: Thomas
authors.affiliation: Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas 75390-9039.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Cooper
authors.affiliation: From the Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom.
authors.forename: Natasha S
authors.initials: NS
authors.lastname: Clayton
authors.affiliation: Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas 75390-9039.
authors.forename: Chensu
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas 75390-9039.
authors.forename: Michael A
authors.initials: MA
authors.lastname: White
authors.affiliation: Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom.
authors.forename: Chris
authors.initials: C
authors.lastname: Abell
authors.affiliation: From the Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom, do202@cam.ac.uk.
authors.forename: Darerca
authors.initials: D
authors.lastname: Owen
authors.affiliation: From the Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom, hrm28@cam.ac.uk.
authors.forename: Helen R
authors.identifier: 0000-0002-7890-7097
authors.initials: HR
authors.lastname: Mott
mesh_terms: D002460:Cell Line; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D010455:Peptides / Q000235:genetics / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D020725:ral GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D010455:Peptides; C483163:Ralb protein, human; D019869:Phosphatidylinositol 3-Kinases; D020725:ral GTP-Binding Proteins; D018631:ras Proteins
keywords: Ral; Ras; autophagy; cell signaling; peptide chemical synthesis; peptides; protein-protein interaction; small GTPase; stapled peptides; therapeutics