The function of MRAS (muscle RAS oncogene homolog, ENSG00000158186) is as follows. Signal transducer in the Ras-MAPK signaling pathway that regulates cell proliferation and survival (PubMed:16630891, PubMed:28289718, PubMed:35768504, PubMed:35830882, PubMed:35831509, PubMed:36175670). Core component of the SHOC2-MRAS-PP1c (SMP) holophosphatase complex that regulates the MAPK pathway activation (PubMed:16630891, PubMed:35768504, PubMed:35830882, PubMed:35831509, PubMed:36175670). The formation of the SMP complex only occurs when MRAS is GTP-bound (PubMed:35768504, PubMed:35830882, PubMed:35831509, PubMed:36175670, PubMed:39809765). Unlike other Ras proteins, MRAS has low intrinsic GTPase activity and may require additional factors for activation (PubMed:39809765). The SMP complex specifically dephosphorylates the inhibitory phosphorylation at 'Ser-259' of RAF1 kinase, 'Ser-365' of BRAF kinase and 'Ser-214' of ARAF kinase, stimulating their kinase activities (PubMed:16630891, PubMed:35768504, PubMed:35830882, PubMed:35831509, PubMed:36175670). Recognized by LZTR1 that mediates its ubiquitination by a BCR (BTB-CUL3-RBX1) E3 ubiquitin- protein ligase complex (PubMed:40934300). {ECO:0000269|PubMed:16630891, ECO:0000269|PubMed:28289718, ECO:0000269|PubMed:35768504, ECO:0000269|PubMed:35830882, ECO:0000269|PubMed:35831509, ECO:0000269|PubMed:36175670, ECO:0000269|PubMed:39809765, ECO:0000269|PubMed:40934300}.