Abstract 2272: Interrogating RAS isoform and mutational specificity for effectors with bioluminescence resonance energy transfer (BRET)

Abstract

Abstract Mutations in the small GTPases HRAS, NRAS, and splice variants KRAS4a and KRAS4b occur in roughly 20% of all cancers1. Each of these four RAS isoforms share a high degree of homology, yet play distinct biological roles; mouse models devoid of KRAS die mid-gestation, whereas HRAS and NRAS null mice survive2. The occurrence of RAS isoform mutations and their specific oncogenic codon substitutions are non-uniform across cancer types, with KRAS mutations in the G12 position frequently driving colorectal cancer while NRAS Q61 mutations are commonly present in skin cancer1. Several explanations have been proposed for this, including differential regulation at the level of transcription, mRNA stability, translation, and protein stability, along with distinctions in post-translational modification, localization, and tissue-specific availability of effectors3. Subtle differences in the biochemical properties of amino acid substitutions may also influence the dominant mutational forms across cancer types. However, the question of whether RAS isoforms and their specific codon substitutions preferentially engage with certain effectors within a cellular context remains unclear, despite considerable efforts. Here, we utilize bioluminescence resonance energy transfer (BRET) between mVenus- and NanoLuc-tagged recombinant proteins to derive quantitative measurements of effector affinity across RAS isoforms and common mutants. By transiently expressing a fixed concentration of NanoLuc-tagged effectors while titrating increasing amounts of mVenus-tagged RAS in a cellular system, we generated saturation curves that reflect the nature of binding between the protein pair in vivo to help untangle this longstanding question. We further validated interactions by immunoprecipitation, and determined construct expression and colocalization via western blot and confocal microscopy. 1Prior IA, Hood FE, Hartley JL. The frequency of Ras mutations in cancer. Cancer Research 20202Malumbres M, Barbacid M. RAS oncogenes: the first 30 years. Nature Reviews Cancer 2003;3:459-653Li S, Balmain A, Counter CM. A model for RAS mutation patterns in cancers: finding the sweet spot. Nature Reviews Cancer 2018;18:767-77 Citation Format: Megan Rigby, John Columbus, Vanessa Wall, Dominic Esposito, Thomas Turbyville. Interrogating RAS isoform and mutational specificity for effectors with bioluminescence resonance energy transfer (BRET) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2272.