 Although it was originally 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 its selective phosphorylation., and its redox-sensitive dimerization However, mounting evidence demonstrated that occludin is not only present in epithelial/endothelial cells, but is also found in large amounts in cells that do not have tight junctions but have very active metabolism