RasIns: Genetically Encoded Intrabodies of Activated Ras Proteins

Area of Science:

• Oncology
• Molecular Biology
• Biotechnology

Background:

• K-Ras and H-Ras are frequently mutated in human cancers, driving tumor growth and poor prognoses.
• Targeting oncogenic Ras proteins is a significant challenge in cancer therapy.

Purpose of the Study:

• To design and develop genetically encoded antibody-like ligands (intrabodies) that specifically recognize active, GTP-bound K-Ras and H-Ras.
• To create tools for monitoring and potentially modulating Ras-mediated signaling pathways.

Main Methods:

• Utilized mRNA display for primary selection of intrabodies against Ras.
• Employed affinity maturation to enhance intrabody binding affinity and selectivity.
• Fused intrabodies with fluorescent proteins for cellular localization studies.

Main Results:

• Developed RasIn1, an intrabody with micromolar affinity (K_D = 2.1μM) for H-Ras(G12V)-GTP, demonstrating high state selectivity and specificity for K- and H-Ras.
• Generated RasIn2 through affinity maturation, achieving nanomolar affinity (K_D = 120nM) while maintaining selectivity.
• Observed colocalization of both intrabodies with Ras proteins and their mutants within cells.
• Demonstrated mutant-selective recognition of G12V Ras mutants over wild-type Ras.

Conclusions:

• Engineered intrabodies (RasIn1 and RasIn2) effectively bind active, GTP-bound K- and H-Ras, including oncogenic mutants.
• These intrabodies exhibit high specificity and selectivity, with potential for mutant-specific targeting.
• The developed intrabodies serve as promising tools for investigating and potentially interfering with Ras signaling in cancer.