Disease relevance of Cldn1

• In the esophagitis rats, the expression of claudin-1 was increased both in the plasma membrane and in the cytoplasm around the erosion in the spinous and granular layers [1].
• The roles of stress responsitive MAP-kinase, p38 MAP-kinase, in the signaling pathway for gap junction protein, Cx32, and tight junction protein, claudin-1, were examined in rat liver in vivo and in vitro, including regeneration following partial hepatectomy and cholestasis after common bile duct ligation [2].

High impact information on Cldn1

• These novel results provide direct evidence of the pivotal role of the claudin family in generating the paracellular physical barrier of tight junctions necessary for spermatogenesis and normal CNS function [3].
• In the pancreas, claudin 2 is only detected in junctions of the duct epithelia, claudin 5 only in junctions of acinar cells, whereas claudin 3 and 4 are in both [4].
• Among differences in the gut are a crypt-to-villus decrease in claudin 2, a highly restricted expression of claudin 4 to colonic surface cells, and the finding that some claudins can be junctional, lateral, or show a gradient in junctional vs. lateral localization along the crypt-to-villus surface axis [4].
• Exogenously expressed JEAP co-localized with ZO-1 and occludin at TJs in polarized Madin-Darby canine kidney cells, but not with claudin-1, JAM, or ZO-1 in L cells [5].
• Neighboring cells formed tight and gap junctions characteristic of epididymal cells in vivo and expressed tight (occludin and claudin-1, -3, and -4) and gap junctional proteins (connexin-26, -30.3, -32, and -43) [6].

Biological context of Cldn1

• Tight junctions in differentiating ameloblasts and odontoblasts differentially express ZO-1, occludin, and claudin-1 in early odontogenesis of rat molars [7].
• These results indicate that regulation of occludin gene expression is different from that of claudin-1, -2, and -3 [8].
• By SB203580 treatment, the down-regulation of Cx32 was inhibited and the up-regulation of claudin-1 was enhanced, well maintaining the structures of gap and tight junctions [9].
• We investigated changes in claudin expression in primary cultured AEC during transdifferentiation to the type I cell-like phenotype (days 0, 1, and 8), and on day 5 in culture +/- EGF (10 ng/ml) from day 0 or day 4 [10].
• 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 [11].

Anatomical context of Cldn1

• Claudin-1 was expressed in endothelial cells of microvessels and in short selected segments of the duct system [12].
• Claudin 2 was not detected in any of the salivary glands [12].
• Claudin-1 was strongly detected at the proximal complex but it was weak at distal complex of late differentiating ameloblasts [7].
• We studied the distribution of ZO-1, occludin, and claudin-1 between differentiating ameloblasts and odontoblasts in molar tooth germs from 1- to 3-day-old rats by confocal laser scanning microscopy [7].
• Heterogeneity of claudin expression by alveolar epithelial cells [13].

Associations of Cldn1 with chemical compounds

• However, methanandamide-treated cells showed a 12-fold increase in claudin-5 expression and a 2- to 3-fold increase in claudin-3, consistent with the notion that specific changes in claudin expression levels may correlate with changes in alveolar epithelial barrier function [13].
• Administration of thyroid hormone to neonates did not affect claudin 2 expression, occludin expression, or the transepithelial resistance in rat proximal tubule cells in vitro [14].
• This hypoxic stress caused an increase in the expression of tight junction proteins claudin-1 and actin, particularly in cells treated with C6-conditioned media [15].
• In EGF induced proliferative rat hepatocytes treated with SB203580, the expression and function of Cx32 and claudin-1 were increased [9].
• PURPOSE: To investigate the expression and cellular distribution of putative tight junction (TJ) proteins occludin, ZO-1, ZO-2, and claudin-1 in rat corneal epithelium and alterations of TJs in cultured human corneal epithelial cells in response to lipopolysaccharide (LPS) challenge [16].

Regulatory relationships of Cldn1

• In the endothelial cells, claudin-5 was stronger expressed than claudin-1 and -2 [17].

Other interactions of Cldn1

• In the cell body-rich area within the DRG, extravascular leakage of EBA was noted and claudin-5 but neither claudin-1 nor occludin was detected [18].
• RESULTS: When p38 MAP-kinase was activated during partial hepatectomy, down-regulation of Cx32 and up-regulation of claudin-1 were observed [9].
• Effects of transdifferentiation and EGF on claudin isoform expression in alveolar epithelial cells [10].
• For this reason, we currently do not have any functional data supporting that PASII/PMP22 is the member of claudin superfamily [19].

Analytical, diagnostic and therapeutic context of Cldn1

• Using immunoblot and immunohistochemistry, we demonstrated that claudin 2 has a 4-fold greater abundance in neonatal proximal tubules than in adult tubules [14].
• Rat endothelial cells showed a characteristic switch of tight junction particles from the P-face to the E-face, accompanied by the loss of claudin-1 in immunofluorescence labeling [20].
• An apparent increase of occludin mRNA expression was detected in livers after 6 h ligation, whereas the expression of claudin-1, -2, and -3 was not influenced by ligation [8].
• At 8 days (D8) after the first dose, testicular expression of the occludin, claudin-1, and -11 was analyzed by semiquantitative RT-PCR [21].
• Immunoblotting detected strong differences among tissues in the expression level of each claudin [4].

References