Membrane-Driven Dimerization of the Peripheral Membrane Protein KRAS: Implications for Downstream Signaling

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• RAS GTPase homo-dimerization at the plasma membrane activates the MAPK pathway, crucial for cell proliferation and oncogenesis.
• Previous structural studies focused on RAS GTPase domains, lacking insights into membrane-bound RAS structures due to the absence of the C-terminal membrane anchor.

Purpose of the Study:

• To investigate the structural characteristics of membrane-anchored KRAS (Kirsten rat sarcoma viral oncogene homolog) homodimers.
• To explore how KRAS dimerization plasticity is influenced by oncogenic mutations, nucleotide states, and lipid composition.
• To utilize nanodisc platforms for screening anticancer drugs targeting KRAS dimers.

Main Methods:

• Utilized lipid-bilayer nanodisc platforms to stabilize membrane-bound RAS proteins.
• Employed paramagnetic relaxation enhancement (PRE) analyses to determine distinct structures of KRAS homodimers.
• Investigated the impact of mutations, nucleotide binding, and lipid environment on KRAS dimerization.

Main Results:

• Revealed distinct structures of membrane-anchored KRAS homodimers, differing in protomer orientation at the α4-α5 interface.
• Demonstrated that the KRAS dimerization interface is highly plastic and sensitive to biological conditions.
• Showed that altered KRAS orientations affect interactions with downstream effectors and regulatory proteins.

Conclusions:

• The plasticity of KRAS dimerization interfaces on the membrane influences its signaling.
• Membrane-bound KRAS dimers present viable targets for novel anticancer therapeutics.
• Nanodisc platforms are effective tools for studying membrane-bound RAS structures and screening drugs.