PPP1R3C (protein phosphatase 1 regulatory subunit 3C) functions as a glycogen-targeting scaffolding subunit for protein phosphatase 1 (PP1), regulating glycogen metabolism and glucose homeostasis. As a regulatory subunit, PPP1R3C activates glycogen synthase while inhibiting glycogen phosphorylase, thereby promoting glycogen synthesis and limiting breakdown 1. The protein dramatically increases basal and insulin-stimulated glycogen synthesis upon overexpression. Mechanistically, PPP1R3C integrates multiple metabolic pathways. It regulates glycolysis and glycolytic capacity in chondrocytes 2 and links glycogen metabolism to thermogenic responses through catecholamine-induced glycogen turnover that generates reactive oxygen species 1. Under stress conditions, PPP1R3C can interact with aryl hydrocarbon receptor to activate glycogenolysis and support pentose phosphate pathway flux for antioxidant NADPH production 3. Clinically, PPP1R3C dysregulation associates with multiple disease states. Low PPP1R3C expression correlates with increased fasting blood glucose in pregnant rats exposed to environmental toxins 4. In cancer, PPP1R3C expression negatively correlates with ovarian cancer survival and stemness 5, while elevated PPP1R3C promotes colorectal cancer progression and rapamycin resistance via mTOR/Myc pathway activation 6. Conversely, miR-4461-mediated PPP1R3C suppression inhibits renal cell carcinoma tumorigenesis 7. These findings establish PPP1R3C as a critical metabolic hub with broad implications for metabolic disease and cancer biology.