Occludin (OCLN) (OCLN)

Occludin is a 65 kDa tetraspan integral membrane protein that serves as a fundamental structural and functional component of tight junctions (TJs) in epithelial and endothelial cells [1, 10]. It is characterized by four transmembrane domains, two extracellular loops, and cytoplasmic N- and C-terminal domains that interact with scaffolding proteins such as zonula occludens-1 (ZO-1) to link the junctional complex to the actin cytoskeleton [5, 17]. Biologically, occludin is critical for maintaining cellular polarity and regulating paracellular permeability, effectively sealing the space between cells to form selective physiological barriers such as the blood-brain barrier (BBB) and the intestinal barrier [3, 4]. In disease states, its downregulation or redistribution due to phosphorylation is associated with the pathophysiology of ischemic stroke, cancer metastasis, and inflammatory bowel disease (IBD) [1, 3, 12]. Furthermore, occludin is a recognized essential host factor and co-receptor for the entry of the Hepatitis C virus (HCV) into hepatocytes [1, 10]. While few drugs target it directly in clinical practice, occludin remains a high-interest target for therapies aimed at barrier modulation and the prevention of viral infections [3, 5, 13].

Other names

OCLNTight junction protein occludin

Occludin acts as an essential host co-receptor for the entry of the Hepatitis C virus (HCV) into hepatocytes by interacting with other cell-surface factors. In its structural role, it regulates the paracellular permeability of tight junctions (TJs); therapeutic strategies focus on stabilizing occludin at the cell membrane to restore barrier integrity in conditions like ischemic stroke or inflammatory bowel disease, or temporary modulation to facilitate drug delivery across the blood-brain barrier.