COSMIC-Linked Ras Mutations at the Interface Between H-Ras and PI3Kγ_RBD Frequently Generate Affinity Increases.

Area of Science:

• Molecular biology
• Cell signaling
• Protein-protein interactions

Background:

• Ras G-proteins (H-, K-, N-Ras) are crucial molecular switches regulating signaling pathways.
• The Ras-PI3K-PIP3-PDK1-AKT pathway is vital for immunity and cell growth, often dysregulated in diseases.
• Ras activation depends on binding affinity with its effectors, like PI3Kγ.

Purpose of the Study:

• To investigate the evolutionary optimization of the H-Ras:PI3Kγ binding interface for affinity.
• To determine if the native interface maximizes binding affinity or provides intermediate affinity.

Main Methods:

• Focused on the H-Ras:PI3Kγ co-complex interface, involving 10 conserved H-Ras residues.
• Introduced 8 specific H-Ras mutations at contact positions, selected from the COSMIC database and literature.
• Assessed the impact of these mutations on H-Ras:PI3KγRBD binding affinity.

Main Results:

• All 8 introduced Ras mutations altered the H-Ras:PI3KγRBD binding affinity.
• Four mutations significantly increased binding affinity, while four significantly decreased it.
• The native H-Ras:PI3KγRBD interface exhibits intermediate, not maximal, binding affinity.

Conclusions:

• The intermediate binding affinity suggests evolutionary adaptation for binding diverse Ras effectors.
• COSMIC mutations at this interface can increase or decrease binding affinity.
• Findings have implications for understanding disease mechanisms and developing cell biology tools.