Year-end Sale % OFF 
Abstract
Tight junctions (TJs) and adherens junctions (AJs) are key determinants of the structure and permeability of epithelial barriers. Although exocytic delivery to the cell surface is crucial for junctional assembly, little is known about the mechanisms controlling TJ and AJ exocytosis. This study was aimed at investigating whether a key mediator of exocytosis, soluble N-ethylmaleimide sensitive factor (NSF) attachment protein alpha (αSNAP), regulates epithelial junctions. αSNAP was enriched at apical junctions in SK-CO15 and T84 colonic epithelial cells and in normal human intestinal mucosa. siRNA-mediated knockdown of αSNAP inhibited AJ/TJ assembly and establishment of the paracellular barrier in SK-CO15 cells, which was accompanied by a significant down-regulation of p120-catenin and E-cadherin expression. A selective depletion of p120 catenin effectively disrupted AJ and TJ structure and compromised the epithelial barrier. However, overexpression of p120 catenin did not rescue the defects of junctional structure and permeability caused by αSNAP knockdown thereby suggesting the involvement of additional mechanisms. Such mechanisms did not depend on NSF functions or induction of cell death, but were associated with disruption of the Golgi complex and down-regulation of a Golgi-associated guanidine nucleotide exchange factor, GBF1. These findings suggest novel roles for αSNAP in promoting the formation of epithelial AJs and TJs by controlling Golgi-dependent expression and trafficking of junctional proteins.
Highlights
Intercellular junctions are the most characteristic morphological features of differentiated epithelia
In contact-naıve, calcium-depleted SK-CO15 colonic epithelial cells, b-catenin demonstrated a diffuse cytosolic labeling, whereas aSNAP accumulated in the perinuclear region (Figure 1B, Figure 1. aSNAP is enriched at epithelial junctions in vitro and in vivo. (A) Dual immunofluorescence labeling and confocal microscopy show colocalization of aSNAP and tight junction protein occludin in confluent T84 cell monolayers and normal human colonic mucosa. (B) Immunofluorescence images show predominantly-perinuclear localization of aSNAP in calcium-depleted SK-CO15 cells and its rapid translocation to newly-formed adherens junctions (AJs) in calcium-repleted cells
Discussion aSNAP regulates AJ and tight junctions (TJs) integrity and establishment of the epithelial barrier aSNAP is a ubiquitously expressed regulator of intracellular vesicle fusion that plays a major role in the disassembly and recycling of various SNARE complexes [37,39]
Summary
Intercellular junctions are the most characteristic morphological features of differentiated epithelia These plasma membrane structures mediate physical interactions between adjacent epithelial cells thereby ensuring the integrity of epithelial layers and creating a barrier to free paracellular passage of different substances. Adhesive properties of epithelial junctions are determined by specialized integral membrane proteins such as the AJ constituent E-cadherin, or the TJ components claudins, occludin, and junctional adhesion molecule (JAM)-A [4,5,6,7,8]. By interacting with their partners on opposing plasma membrane, these integral proteins mediate cell-cell attachment and formation of the paracellular barrier. Components of the AJ cytosolic plaque, a-, b- and p120 catenins, and the TJ plaque proteins, zonula occludens (ZO) enhance adhesive properties of epithelial junctions and regulate AJ/TJ biogenesis [5,6,7,8,9]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
