CLIC2 is a multifunctional X-linked protein that exists in both soluble and membrane-bound forms. In its soluble state, CLIC2 catalyzes glutathione-dependent redox reactions and displays glutathione peroxidase activity 1, while maintaining a monomeric structure with an intramolecular disulfide bond regardless of redox conditions 2. Upon membrane insertion—a redox-regulated process—CLIC2 forms pH-dependent chloride channels 2 and modulates ryanodine receptor activity to inhibit calcium influx. CLIC2 plays critical roles in tissue homeostasis and immune regulation. In endothelial cells, CLIC2 associates with tight junction proteins (claudins, occludin, ZO-1) and is essential for maintaining barrier integrity; CLIC2 knockdown permits cancer cell transmigration 3. During monocyte-to-macrophage differentiation, CLIC2 regulates the Stat3 signaling pathway through interaction with Shp1 phosphatase, modulating cytokine secretion and promoting a tumor-permissive microenvironment 4. CLIC2 has disease relevance in multiple contexts. Anti-CLIC2 autoantibodies correlate with systemic lupus erythematosus disease activity (SLEDAI score ≥6) 5, suggesting potential as a biomarker. CLIC2 is implicated in gastric cancer progression 4 and cancer metastasis through effects on endothelial barrier function 3. While CLIC2 was proposed as an X-linked intellectual disability gene, large-scale sequencing studies question this association 6, warranting further replication studies.