CLDN2 (claudin-2) is a tight junction protein that forms paracellular cation- and water-selective channels in epithelial barriers 1. In the intestine, CLDN2 regulates sodium and water flux to control nutrient absorption and immune homeostasis 1. CLDN2 expression is tightly regulated through autophagy-mediated degradation via clathrin-dependent endocytosis and AP2M1-LC3 interactions; autophagy-induced CLDN2 degradation enhances barrier function by reducing paracellular permeability 1. Dysregulated CLDN2 has significant pathological consequences. Elevated CLDN2 expression in sepsis increases intestinal permeability, promotes pathogenic dysbiosis, enhances immune activation, and increases mortality, while CLDN2 knockout dramatically improves survival 2. Conversely, in inflammatory bowel disease, CLDN2 upregulation promotes mucosal healing downstream of EGFR signaling and protects against colitis-associated cancer through Survivin regulation 3. CLDN2 variants (rs7057398) are genetically associated with acute pancreatitis susceptibility in Caucasians 4, and CLDN2 mutations contribute to hereditary pancreatitis pathogenesis 5. These findings indicate CLDN2's context-dependent role: while promoting recovery in IBD, elevated CLDN2 worsens sepsis outcomes, suggesting therapeutic potential as a target in septic patients.