Regulatory subunit of protein phosphatase 1 (PP1c) that acts as a M-Ras/MRAS effector and participates in MAPK pathway activation. Upon M-Ras/MRAS activation, targets PP1c to specifically dephosphorylate the 'Ser-259' inhibitory site of raf1 kinase and stimulate raf1 activity at specialized signaling complexes (By similarity). Belongs to the SHOC2 family.