PPP1CB (protein phosphatase 1 catalytic subunit beta) is a serine/threonine phosphatase that functions as a catalytic component of multiple regulatory complexes controlling diverse biological processes. As a core component of the SHOC2-MRAS-PP1c (SMP) holophosphatase complex, PPP1CB dephosphorylates inhibitory phosphorylation sites on RAF family kinases (RAF1 at Ser-259, BRAF at Ser-365, ARAF at Ser-214), thereby stimulating MAPK pathway activation 123. PPP1CB also participates in the PTW/PP1 phosphatase complex regulating chr2 structure and cell cycle progression, and modulates circadian rhythm through PER1 and PER2 dephosphorylation [UniProt annotations]. Beyond MAPK signaling, PPP1CB has documented roles in lung adenocarcinoma glycolysis suppression via STAT3 dephosphorylation 4 and in immune regulation, including FOXP3 dephosphorylation in regulatory T cells [UniProt]. Clinically, PPP1CB mutations are associated with Noonan syndrome and Noonan syndrome-like disorders 5, intellectual disability 6, and lupus nephritis with RASopathy features 7. PPP1CB emerges as a diagnostic candidate gene in osteoporosis with sarcopenia 8 and rheumatoid arthritis 9, suggesting broader disease relevance beyond developmental disorders.