Occludin

[5] Together with Claudins, and zonula occludens-1 (ZO-1), occludin has been considered a staple of tight junctions, and although it was shown to regulate the formation, maintenance, and function of tight junctions, its precise mechanism of action remained elusive and most of its actions were initially attributed to conformational changes following selective phosphorylation,[6] and its redox-sensitive dimerization.[16] Furthermore, manipulation of occludin content in human cells is capable of influencing the expression of glucose transporters,[16] and the activation of transcription factors like NFkB, and histone deacetylases like sirtuins, which proved capable of diminishing HIV replication rates in infected human macrophages under laboratory conditions.Indeed, MDCK cells lacking occludin and its homolog tricellulin exhibit less complex tight junction strand network and impaired barrier function.[22] Furthermore, studies in which mice were deprived of occludin expression showed morphological stability in several epithelial tissues but also found chronic inflammation and hyperplasia in the gastric epithelium, calcification in the brain, testicular atrophy, loss of cytoplasmic granules in straited duct cells of salivary gland, and thinning of the compact bone.In standard cells, loss or disruption of occludin and other tight junction proteins leads to initiation of apoptosis through extrinsic pathways.