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Updated: Jul 4, 2025
Construction of Model Lipid Membranes Incorporating G-protein Coupled Receptors GPCRs
Published on: February 5, 2022
RAS G-domains allosterically contribute to the recognition of lipid headgroups and acyl chains
Neha Arora1, Huanwen Mu2, Hong Liang1
1Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center, Houston, TX, USA.
Abstract:
Mutant RAS are major contributors to cancer and signal primarily from nanoclusters on the plasma membrane (PM). Their C-terminal membrane anchors are main features of membrane association. However, the same RAS isoform bound to different guanine nucleotides spatially segregate. Different RAS nanoclusters all enrich a phospholipid, phosphatidylserine (PS). These findings suggest more complex membrane interactions. Our electron microscopy-spatial analysis shows that wild-types, G12V mutants, and membrane anchors of isoforms HRAS, KRAS4A, and KRAS4B prefer distinct PS species. Mechanistically, reorientation of KRAS4B G-domain exposes distinct residues, such as Arg 135 in orientation state 1 (OS1) and Arg 73/Arg 102 in OS2, to the PM and differentially facilitates the recognition of PS acyl chains. Allele-specific oncogenic mutations of KRAS4B also shift G-domain reorientation equilibrium. Indeed, KRAS4BG12V, KRAS4BG12D, KRAS4BG12C, KRAS4BG13D, and KRAS4BQ61H associate with PM lipids with headgroup and acyl chain specificities. Distribution of these KRAS4B oncogenic mutants favors different nanoscale membrane topography. Thus, RAS G-domains allosterically facilitate membrane lateral distribution.
Insights
RAS proteins, key in cancer, interact with specific membrane lipids like phosphatidylserine (PS). Oncogenic mutations alter RAS G-domain orientation, influencing their association with distinct membrane nanoclusters and lipid species.
Area of Science:
- Molecular Biology
- Cell Biology
- Biophysics
Background:
- Mutant RAS proteins are critical drivers of cancer, initiating signaling from plasma membrane nanoclusters.
- RAS protein association with the plasma membrane is primarily mediated by their C-terminal membrane anchors.
- Different RAS isoforms exhibit distinct spatial segregation when bound to varying guanine nucleotides, and RAS nanoclusters enrich phosphatidylserine (PS).
Purpose of the Study:
- To investigate the complex membrane interactions of RAS proteins, particularly their specificity towards different phosphatidylserine (PS) species.
- To elucidate the mechanistic basis for RAS protein localization and distribution within distinct membrane nanoclusters.
- To determine how oncogenic mutations in KRAS4B affect its interaction with plasma membrane lipids.
Main Methods:
- Electron microscopy coupled with spatial analysis to examine wild-type and mutant RAS protein interactions with membrane anchors.
- Analysis of RAS G-domain reorientation states and their impact on residue exposure and PS acyl chain recognition.
- Investigating the lipid headgroup and acyl chain specificities of oncogenic KRAS4B mutants' association with plasma membrane lipids.
Main Results:
- Wild-type RAS, G12V mutants, and HRAS, KRAS4A, and KRAS4B membrane anchors demonstrate preferential binding to distinct PS species.
- KRAS4B G-domain reorientation exposes different residues (e.g., Arg 135 in OS1, Arg 73/102 in OS2), modulating PS acyl chain recognition.
- Oncogenic KRAS4B mutations (G12V, G12D, G12C, G13D, Q61H) exhibit specific headgroup and acyl chain preferences for plasma membrane lipids, favoring distinct nanoscale membrane topographies.
Conclusions:
- RAS G-domains allosterically regulate their lateral distribution within the plasma membrane.
- Specific interactions between RAS G-domains, PS lipids, and membrane nanoclusters are crucial for RAS signaling and oncogenesis.
- Understanding these lipid-protein interactions provides insights into targeted cancer therapies.
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