SCRN1 (secernin 1) is a regulator of exocytosis with diverse roles in cellular physiology and disease. In its canonical function, SCRN1 regulates mast cell exocytosis and increases cellular secretion sensitivity to calcium stimulation 1. Beyond this, SCRN1 plays critical roles in neuronal function through VAP-SCRN1 interactions at the endoplasmic reticulum membrane, which modulate synaptic vesicle cycling, ER remodeling, and presynaptic calcium homeostasis 2. In cancer pathogenesis, SCRN1 promotes tumor progression through multiple mechanisms. In hepatocellular carcinoma, SCRN1 confers ferroptosis resistance by stabilizing GPX4 via STK38-mediated phosphorylation, reducing lipid peroxidation and cell death 3. In colorectal and oral squamous cell carcinomas, SCRN1 enhances matrix metalloproteinase (MMP)-2/9 exocytosis and promotes cell proliferation, invasion, and migration via TGF-β/Smad3 signaling 41. High SCRN1 expression correlates with poor prognosis in colorectal cancer 5. Clinically, SCRN1 emerges as a biomarker in neurodegenerative disease. CSF SCRN1 levels are significantly elevated in Alzheimer's disease, correlating strongly with tau pathology (total tau and phosphorylated tau181) and disease severity, but remain unchanged in other tauopathies 6. SCRN1 also represents a potential immunotherapy target for gastric cancer based on its tumor-associated antigen properties 7.