Membrane-mediated induction and sorting of K-Ras microdomain signaling platforms

Academic Article

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 (ld) 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 ld phase and concentrate at the ld/lo 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. © 2010 American Chemical Society.
  • Digital Object Identifier (doi)

    Author List

  • Weise K; Kapoor S; Denter C; Nikolaus J; Opitz N; Koch S; Triola G; Herrmann A; Waldmann H; Winter R
  • Start Page

  • 880
  • End Page

  • 887
  • Volume

  • 133
  • Issue

  • 4