Heterogeneity in expression and subcellular localization of tight junction proteins, claudin-10 and -15, examined by RT-PCR and immunofluorescence microscopy

Abstract

Tight junctions regulate paracellular permeability, create the luminal fluid microenvironment of blood vessels and the digestive tract, and also form the protective barrier in the stratified epithelium including the epidermis. Claudins are the integral membrane proteins at tight junctions and form a multigene family composed of at least 24 members, but knowledge of the subcellular localization of each claudin is still fragmentary. We performed RT-PCR for fifteen claudin species to examine the mRNA expression in various mouse tissues, and focused on investigating the subcellular localization of claudin-10 and -15 by immunofluorescence microscopy in various rat tissues. Neither claudin-10 nor -15 was detected in vascular endothelial cells in most tissues, and these claudins were restricted to the vasa recta in the kidney medulla. Both claudins were also detected at apical tight junctions in the epithelium of the jejunum with no intensity gradients along the crypt-to-villus axis. However, both claudins were expressed only in the basal half of the crypt epithelium in the colon, showing obvious gradients along crypt-to-surface axis. Moreover, claudin-10 showed the ectopic subcellular localization where tight junction strands do not exist. Claudin-10 was detected along the entire lateral membranes of acinar cells in addition to the apical tight junctions in exocrine glands, and in the cytoplasm of basal cells in the stratified epithelium including the dorsal skin and cutaneous stomach. These heterogeneous distributions of claudin-10 and -15 in tissues may be related to the differences in paracellular permeability among tissues.

Molecular Staging of Epithelial Maturation Using Secretory Cell–Specific Genes as Markers

“…However, claudins-1 and -4 were found along the entire lateral membrane, while claudin-7 was located along the lateral membrane and excluded from the tight junction (32). Cldn10 has been localized along the entire lateral membrane of exocrine glands and scattered epithelial cells of the cecum (31,33). Our work colocalizes Cldn10 with b-catenin, an adherens junction protein.…”

Claudin-10 exists in six alternatively spliced isoforms that exhibit distinct localization and function

“…As both the N-terminus and C-terminus reside in the cytoplasm, there are two extracellular loops through which claudins of neighbouring cells are assumed to interact, as they have been demonstrated to exhibit a barrier function and to regulate paracellular permeability (Wen et al, 2004;Hou et al, 2005). In tubular epithelia, a segment-specific distribution of different claudins is observed (Kiuchi-Saishin et al, 2002;Hashizume et al, 2004;Guan et al, 2005;Inai et al, 2005;Holmes et al, 2006;Ohta et al, 2006). Amongst these is claudin-10 which is differentially expressed along the length of many tubular epithelia including the nephron in the kidney.…”

HE6/GPR64 adhesion receptor co-localizes with apical and subapical F-actin scaffold in male excurrent duct epithelia

“…The list of downregulated gene products included claudin-10, member of a family of tight junction proteins. Claudin proteins create the tissue-specific and regional differences in paracellular conductance of various epithelia, including epithelia of the male genital tract (Inai et al 2005, Holmes et al 2006.…”