Membrane interactions of the globular domain and the hypervariable region of KRAS4b define its unique diffusion...

Area of Science:

• Cellular Biology
• Molecular Biology
• Biophysics

Background:

• RAS proteins function as GTP-dependent switches controlling critical signaling pathways.
• RAS proteins localize to specific plasma membrane nanodomains through lipid anchors and protein interactions.
• Understanding RAS dynamics and activation mechanisms is crucial, especially given their frequent mutation in cancer.

Purpose of the Study:

• To characterize the membrane dynamics and mobility of RAS proteins in live cells.
• To elucidate the distinct mobility parameters of different RAS isoforms, particularly KRAS4b.
• To reveal the molecular mechanisms underlying altered KRAS4b mobility, especially in oncogenic contexts.

Main Methods:

• Single-molecule tracking in live human and mouse cells.
• Estimation of RAS protein mobility parameters.
• Molecular dynamics simulations and complementary experimental approaches.

Main Results:

• KRAS4b displays confined mobility with three distinct diffusive states, differentiating it from KRAS4a, NRAS, and HRAS.
• The globular domain, not solely the hypervariable region, significantly contributes to KRAS4b's restricted movement.
• A detailed mechanism for altered oncogenic KRAS4b mobility was elucidated.

Conclusions:

• RAS protein isoforms exhibit distinct membrane dynamics, with KRAS4b showing unique confined mobility.
• The structural basis for KRAS4b's altered dynamics involves its globular domain.
• These findings provide mechanistic insights into RAS signaling and its role in cancer.