title: Membrane-mediated induction and sorting of K-Ras microdomain signaling platforms.
abstract: The K-Ras4B GTPase is a major oncoprotein whose signaling activity depends on its correct localization to negatively charged subcellular membranes and nanoclustering in membrane microdomains. Selective localization and clustering are mediated by the polybasic farnesylated C-terminus of K-Ras4B, but the mechanisms and molecular determinants involved are largely unknown. In a combined chemical biological and biophysical approach we investigated the partitioning of semisynthetic fully functional lipidated K-Ras4B proteins into heterogeneous anionic model membranes and membranes composed of viral lipid extracts. Independent of GDP/GTP-loading, K-Ras4B is preferentially localized in liquid-disordered (l(d)) lipid domains and forms new protein-containing fluid domains that are recruiting multivalent acidic lipids by an effective, electrostatic lipid sorting mechanism. In addition, GDP-GTP exchange and, thereby, Ras activation results in a higher concentration of activated K-Ras4B in the nanoscale signaling platforms. Conversely, palmitoylated and farnesylated N-Ras proteins partition into the l(d) phase and concentrate at the l(d)/l(o) phase boundary of heterogeneous membranes. Next to the lipid anchor system, the results reveal an involvement of the G-domain in the membrane interaction process by determining minor but yet significant structural reorientations of the GDP/GTP-K-Ras4B proteins at lipid interfaces. A molecular mechanism for isoform-specific Ras signaling from separate membrane microdomains is postulated from the results of this study.
authors.affiliation: Physical Chemistry I, Biophysical Chemistry, Faculty of Chemistry, TU Dortmund University , Otto-Hahn-Strasse 6, D-44227 Dortmund, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Weise
authors.forename: Shobhna
authors.initials: S
authors.lastname: Kapoor
authors.forename: Christian
authors.initials: C
authors.lastname: Denter
authors.forename: Jörg
authors.initials: J
authors.lastname: Nikolaus
authors.forename: Norbert
authors.initials: N
authors.lastname: Opitz
authors.forename: Sebastian
authors.initials: S
authors.lastname: Koch
authors.forename: Gemma
authors.initials: G
authors.lastname: Triola
authors.forename: Andreas
authors.initials: A
authors.lastname: Herrmann
authors.forename: Herbert
authors.initials: H
authors.lastname: Waldmann
authors.forename: Roland
authors.initials: R
authors.lastname: Winter
mesh_terms: D000595:Amino Acid Sequence; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D009980:Influenza A virus / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D050356:Lipid Metabolism; D021962:Membrane Microdomains / Q000737:chemistry / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D016283:Proto-Oncogene Proteins p21(ras) / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D017550:Spectroscopy, Fourier Transform Infrared; D053835:Unilamellar Liposomes / Q000737:chemistry / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D053835:Unilamellar Liposomes; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D016283:Proto-Oncogene Proteins p21(ras)