Abstract
The protein K-Ras functions as a molecular switch in signaling pathways regulating cell growth. In the human mitogen-activated protein kinase (MAPK) pathway, which is implicated in many cancers, multiple K-Ras proteins are thought to assemble at the cell membrane with Ras effector proteins from the Raf family. Here we propose an atomistic structural model for such an assembly. Our starting point was an asymmetric guanosine triphosphate-mediated K-Ras dimer model, which we generated using unbiased molecular dynamics simulations and verified with mutagenesis experiments. Adding further K-Ras monomers in a head-to-tail fashion led to a compact helical assembly, a model we validated using electron microscopy and cell-based experiments. This assembly stabilizes K-Ras in its active state and presents composite interfaces to facilitate Raf binding. Guided by existing experimental data, we then positioned C-Raf, the downstream kinase MEK1 and accessory proteins (Galectin-3 and 14-3-3σ) on and around the helical assembly. The resulting Ras-Raf signalosome model offers an explanation for a large body of data on MAPK signaling.
© 2021. The Author(s), under exclusive licence to Springer Nature America, Inc.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Blood Proteins / chemistry
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Blood Proteins / metabolism
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DNA-Binding Proteins / chemistry
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DNA-Binding Proteins / metabolism
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Fluorescence Resonance Energy Transfer
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GTPase-Activating Proteins / chemistry
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GTPase-Activating Proteins / metabolism
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Galectins / chemistry
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Galectins / metabolism
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Guanosine Triphosphate / chemistry
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Guanosine Triphosphate / metabolism
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HEK293 Cells
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Humans
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MAP Kinase Kinase 1 / metabolism
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Microscopy, Electron
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Microscopy, Electron, Transmission
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Molecular Dynamics Simulation
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Multiprotein Complexes / chemistry
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Multiprotein Complexes / metabolism
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Mutagenesis
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Protein Multimerization
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Proto-Oncogene Proteins c-raf / chemistry*
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Proto-Oncogene Proteins c-raf / genetics
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Proto-Oncogene Proteins c-raf / metabolism*
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Proto-Oncogene Proteins p21(ras) / chemistry*
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Proto-Oncogene Proteins p21(ras) / genetics
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Proto-Oncogene Proteins p21(ras) / metabolism*
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Reproducibility of Results
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Signal Transduction
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Transcription Factors / chemistry
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Transcription Factors / metabolism
Substances
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Blood Proteins
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DNA-Binding Proteins
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GTPase-Activating Proteins
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Galectins
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KRAS protein, human
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LGALS3 protein, human
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Multiprotein Complexes
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SLC2A4RG protein, human
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Transcription Factors
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Guanosine Triphosphate
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Proto-Oncogene Proteins c-raf
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Raf1 protein, human
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MAP Kinase Kinase 1
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MAP2K1 protein, human
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Proto-Oncogene Proteins p21(ras)