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Interaction of KRas4B protein with C6-ceramide containing lipid model membranes

Lei Li1, Mridula Dwivedi2, Nelli Erwin1

  • 1Faculty of Chemistry and Chemical Biology, Physical Chemistry I, Technical University of Dortmund, Otto-Hahn-Strasse 4a, 44221 Dortmund, Germany; International Max Planck Research School (IMPRS) in Chemical and Molecular Biology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany.

Biochimica Et Biophysica Acta. Biomembranes
|January 23, 2018
PubMed

Insights

C6-ceramide inhibits KRas4B mutated cancer cells by altering their membrane organization. KRas4B forms nanoclusters, reducing protein stability without direct C6-ceramide interaction, revealing a novel inhibition mechanism.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Cancer Research

Background:

  • Ras proteins are crucial oncoproteins in cellular signaling, with mutations driving over 30% of cancers.
  • KRas4B is the most frequently mutated Ras isoform, and its signaling depends on cell membrane localization.
  • C6-ceramide inhibits KRas4B mutated cell growth, but the underlying mechanism is unknown.

Purpose of the Study:

  • To elucidate the molecular mechanism by which C6-ceramide inhibits KRas4B mutated cells.
  • To investigate the effect of C6-ceramide on KRas4B localization and behavior within a model biomembrane.

Main Methods:

  • Established a heterogeneous model biomembrane incorporating C6-ceramide.
  • Utilized fluorescence cross-correlation spectroscopy to study KRas4B-lipid interactions.
  • Employed Förster Resonance Energy Transfer (FRET)-based binding assays to assess KRas4B protein stability.

Main Results:

  • C6-ceramide incorporation did not disrupt the model lipid membrane.
  • KRas4B formed small, monodisperse nanoclusters in a fluid-like environment, suggesting a lipid sorting mechanism.
  • No direct interaction was observed between C6-ceramide and KRas4B; KRas4B recruited other lipids.
  • The stability of KRas4B proteins in the C6-ceramide-containing membrane was reduced.

Conclusions:

  • C6-ceramide inhibits KRas4B mutated cells by altering membrane organization and reducing KRas4B protein stability.
  • The mechanism involves KRas4B forming nanoclusters and recruiting other lipids, rather than direct interaction with C6-ceramide.
  • This study provides a molecular basis for C6-ceramide's anti-cancer activity against KRas4B mutations.

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