CLIC4 (chloride intracellular channel 4) is a multifunctional protein with dual roles in cellular homeostasis and disease pathology. In its soluble state, CLIC4 catalyzes glutaredoxin-like thiol-disulfide exchange reactions 1, while membrane-inserted forms create voltage-dependent chloride channels under redox-regulated conditions 2. CLIC4 localizes to the nucleus upon cellular stress (DNA damage, TNF-α, TGF-β stimulation) where it enhances TGF-β signaling by stabilizing phosphorylated Smad2/3, promoting growth arrest and apoptosis 3. Additionally, CLIC4 regulates endothelial function through multiple mechanisms: it mediates PAR1-dependent RhoA activation controlling barrier integrity 4, activates Arf6-mediated endosomal trafficking affecting BMPRII expression 5, and promotes alveolar cell plasticity via the PCLAF-DREAM complex during lung regeneration 6. CLIC4 is essential for successful cytokinesis by bridging plasma membrane and actin cytoskeleton through ezrin activation 7. In cancer, CLIC4 expression is paradoxically reduced and excluded from tumor cell nuclei (loss of tumor suppressor function) but upregulated in tumor-associated myofibroblasts, marking malignant progression 89. Reactivation of nuclear CLIC4 in tumor cells suppresses growth, suggesting therapeutic potential.