Subcellular Distribution of Tight Junction-Associated Proteins (Occludin, ZO-1, ZO-2) in Rodent Skin

• Published in: Journal of investigative dermatology Vol. 110; no. 6; pp. 862 - 866
• Main Authors: Morita, Kazumasa, Itoh, Masahiko, Saitou, Mitinori, Ando-Akatsuka, Yuhko, Furuse, Mikio, Yoneda, Kozo, Imamura, Sadao, Fujimoto, Kazushi, Tsukita, Shoichiro
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.06.1998
• Subjects: Animals; Animals, Newborn; Cells, Cultured; Epithelial Cells - chemistry; Female; Freeze Fracturing; Frozen Sections; Immunoblotting; Immunohistochemistry; Male; Membrane Proteins - analysis; Mice; Microscopy, Fluorescence; Microscopy, Immunoelectron; Occludin; Phosphoproteins - analysis; Skin - chemistry; Skin - cytology; Skin - ultrastructure; Subcellular Fractions - chemistry; tight junction; Tight Junctions - chemistry; Tight Junctions - ultrastructure; ZO-1; ZO-2; Zonula Occludens-1 Protein; Zonula Occludens-2 Protein; ZO-2; occludin; ZO-1; tight junction
• ISSN: 0022-202X; 1523-1747
• DOI: 10.1046/j.1523-1747.1998.00209.x

Occludin is an integral membrane protein that is concentrated at tight junctions (zonulae occludentes) in simple epithelial cells. ZO-1 and ZO-2 are peripheral membrane proteins that are localized at tight junctions in simple epithelial cells and at cadherin-based adherens junctions in nonepithelial cells. In this study, we investigated the expression and subcellular distribution of occludin, ZO-1, and ZO-2 in rodent skin. Immunoblotting detected all of these molecules in isolated epidermis, but the occludin/ZO-1 (or occludin/ZO-2) ratio was significantly lower than that in cultured simple epithelial cells. In the epidermis of adult skin, occludin was concentrated at cell–cell borders only in the most superficial zone of the granular cell layer, whereas ZO-1 and ZO-2 were distributed in a much broader zone from the spinous to the granular layers. During mouse skin development, this peculiar distribution of occludin in the epidermis appeared when the periderm, a simple epithelium bearing typical occludin-based tight junctions, was sloughed off at embryonic day 16.5 of gestation. Freeze-fracture electron microscopy identified the so-called focal strands or maculae occludentes, i.e., spot tight junction-like structures, between adjacent granular cells, and anti-occludin monoclonal antibody exclusively labeled these focal strands. In hair follicles, occludin and ZO-1 were colocalized at cell–cell borders in Henle’s layer and the cornifying cuticle of the inner root sheath. In addition, ZO-1 but not occludin were localized weakly at the outer root sheath and intensely at the hair cortex/matrix.