CNPY4 (canopy FGF signaling regulator 4) is a conserved saposin-like protein that regulates cellular signaling through multiple mechanisms. As a primary function, CNPY4 modulates cell surface expression of TLR4 and participates in protein localization to the plasma membrane 1. Mechanistically, CNPY4 acts as a negative regulator of Hedgehog (HH) pathway signaling by controlling membrane sterol lipid composition; Cnpy4 knockout embryos exhibit HH signaling perturbations including digit abnormalities, while Cnpy4 knockdown hyperactivates HH signaling and elevates membrane cholesterol levels 2. CNPY4 also functions as a substrate of the kinase FAM20C, where its phosphorylation contributes to proinflammatory adipocyte signaling and metabolic dysfunction 3. Disease relevance includes involvement in developmental processes, immune regulation, and metabolic disorders. Regarding clinical significance, CNPY4 expression is differentially regulated in endometrial stromal cells from women with recurrent pregnancy loss and repeated implantation failure compared to fertile controls, suggesting a potential biomarker role in reproductive pathology 4. CNPY4 interacts with the tumor suppressor LRIG1, implicating it in growth factor receptor regulation networks 5. Further research is needed to fully elucidate CNPY4's therapeutic potential in metabolic and immunological diseases.