GNG2-MRAS interaction regulates SHOC2-dependent RAF activation and MAPK signaling

The interaction between GNG2 and the MRAS protein plays a significant role in regulating the SHOC2-dependent RAF activation and MAPK signaling pathway. This pathway is often dysregulated in various human cancers and RASopathies. The SHOC2-MRAS-PP1C complex, also known as SMP, is a key regulatory component of this pathway, activating it through the dephosphorylation of RAF kinases, which in turn relieves their autoinhibition.

Although GNG2, a subunit of heterotrimeric G proteins, has been shown to negatively modulate MAPK signaling, the exact mechanism of this action has been unclear. This study reveals that GNG2 and its truncated versions are inhibitors of SMP complex assembly by directly targeting MRAS. Using various techniques such as NanoBiT live-cell bioluminescence, co-immunoprecipitation, biolayer interferometry, and molecular dynamics simulations, researchers demonstrate that the full-length GNG2 (residues 1-71aa) and two helical fragments (Delta1, residues 1-29aa, and Delta2, residues 30-71aa) bind to MRAS.

These interactions disrupt SMP complex formation and inhibit RAF dephosphorylation. When cells express these truncated GNG2 variants, there is a significant reduction in phosphorylation of ERK, indicating inhibition of the pathway's activation.

Moreover, a short peptide derived from the GNG2 Delta2 sequence effectively disrupts SMP complex formation in both purified protein systems and live cells, and effectively suppresses MAPK signaling. Molecular dynamics simulations show that GNG2 variants interact with the Switch I/II regions of MRAS, interfering with SHOC2-PP1C association.

The study thus identifies GNG2 as a direct regulator of SMP complex assembly, and suggests that GNG2-derived peptides could serve as a promising approach to disrupt SHOC2-MRAS interactions and dampen MAPK signaling in RAS/RAF-driven pathologies.