The 'undruggable' oncogene finally targeted–where mutation-specific drugs exploit unique protein conformations.
KRAS cycles between active (GTP-bound) and inactive (GDP-bound) states. GTPase-activating proteins (GAPs) accelerate GTP hydrolysis; guanine nucleotide exchange factors (GEFs) promote GTP loading. Oncogenic mutations impair GTPase activity, locking KRAS in the active state.
Active KRAS engages effector proteins (RAF, PI3K) through protein-protein interactionsLoading..., driving downstream signaling cascades that promote proliferation and survival.
What KRAS Does: KRAS is a molecular switch that cycles between "on" (GTP-bound) and "off" (GDP-bound). It transmits growth signals from receptors to downstream pathways.
When Mutated: Oncogenic KRAS mutations lock it in the "on" position, constantly signaling growth regardless of upstream signals.
KRAS's smooth surface and picomolar GTP affinity made traditional drug design impossible. The breakthrough came from recognizing that G12C creates a unique druggable pocket. Covalent inhibitors form irreversible bonds with the mutant cysteine, trapping KRAS in the inactive GDP-bound state.
Sotorasib (2021) and adagrasib (2022) are approved for KRAS G12C-mutant NSCLCLoading.... However, G12C represents only ~13% of KRAS mutations–G12D and G12V (more common) remain challenging targets.
Historic Challenge: For decades, KRAS was considered "undruggable"—its smooth surface offered no pocket for drugs to bind.
Recent Breakthroughs: Sotorasib and adagrasib now target the G12C mutation. Other mutations are being targeted with newer approaches.
KRAS function depends on effector protein interactions. Active KRAS binds RAF ('MAPK pathway) and PI3K ('Akt pathway) through specific protein-protein interactionLoading... domains. Different KRAS mutations may preferentially engage different effectors.
FRET-based measurement of KRAS-effector interactions could potentially assess pathway engagement and predict which downstream inhibitors might be effective in combination with KRAS inhibitors.
Signaling Through Interactions: KRAS works by interacting with effector proteins (RAF, PI3K). Measuring these interactions could potentially assess pathway activity.
Downstream Readout: The validated Akt activation assay provides one window into KRAS pathway output, since PI3K/Akt is a major KRAS effector pathway.
