Bves Modulates Tight Junction Associated Signaling

Abstract

Blood vessel epicardial substance (Bves) is a transmembrane adhesion protein that regulates tight junction (TJ) formation in a variety of epithelia. The role of TJs within epithelium extends beyond the mechanical properties. They have been shown to play a direct role in regulation of RhoA and ZONAB/DbpA, a y-box transcription factor. We hypothesize that Bves can modulate RhoA activation and ZONAB/DbpA activity through its regulatory effect on TJ formation. Immortalized human corneal epithelial (HCE) cells were stably transfected with Flag-tagged full length chicken Bves (w-Bves) or C-terminus truncated Bves (t-Bves). We found that stably transfected w-Bves and t-Bves were interacting with endogenous human Bves. However, interaction with t-Bves appeared to disrupt cell membrane localization of endogenous Bves and interaction with ZO-1. w-Bves cells exhibited increased TJ function reflected by increased trans-epithelial electrical resistance, while t-Bves cells lost TJ protein immunolocalization at cell-cell contacts and exhibited decreased trans-epithelial electrical resistance. In parental HCE and w-Bves cells ZONAB/DbpA and GEF-H1 were seen at cell borders in the same pattern as ZO-1. However, expression of t-Bves led to decreased membrane localization of both ZONAB/DbpA and GEF-H1. t-Bves cells had increased RhoA activity, as indicated by a significant 30% increase in FRET activity compared to parental HCE cells. ZONAB/DbpA transcriptional activity, assessed using a luciferase reporter probe, was increased in t-Bves cells. These studies demonstrate that Bves expression and localization can regulate RhoA and ZONAB/DbpA activity.

Expression and distribution of symplekin regulates the assembly and function of the epithelial tight junction

“…It is believed that ZO-1 acts as a scaVolding protein that forms a foundation for tight junction assembly (Tsukita et al 2001). Indeed, loss of ZO-1 leads to the failure of tight junction formation (Georgiadis et al 2010;Russ et al 2011). In this investigation, we observed that symplekin and ZO-1 showed almost the same immunoXuorescence staining pattern at the tight junction in 2.5-D cell cultures, while our co-immunoprecipitation results indicated that symplekin and ZO-1 form a protein-protein complex in both HT-29 and Caco-2 epithelial cells.…”

Tight junctions: from simple barriers to multifunctional molecular gates

“…CFTR, the transmembrane protein linked to cystic fibrosis, binds and stabilises ZO-1, leading to reduced ZO-1 expression in its absence and, thereby, promoting nuclear translocation of ZONAB, induction of cyclin D1 and repression of ErbB2 147 . Manipulation of other junctional transmembrane proteins, such as BVES, regulates ZONAB activation via a GEF-H1/RhoA-stimulated mechanism 140,148 . In endothelial cells of the blood-tumour-barrier, bradykinin-induced activation of nitric oxide synthesis induces increased permeability and ZONAB activation, leading to repression of claudin-5 and occludin promoters 149 .…”

Signalling at tight junctions during epithelial differentiation and microbial pathogenesis

“…2) (Aijaz et al, 2005;Benais-Pont et al, 2003;Guillemot et al, 2008a). Binding to cingulin results in the inhibition of GEF-H1 and is promoted by tight junction formation that is induced by the junctional membrane protein BVES; hence, junctional GEF-H1 is thought to be inactive (Aijaz et al, 2005;Russ et al, 2011). If it is not sequestered at tight junctions, GEF-H1 promotes various RhoA-driven processes, including cell spreading and migration, cell cycle progression and gene expression (Birukova et al, 2006;Kakiashvili et al, 2009;Krendel et al, 2002;Nie et al, 2009;Terry et al, 2011;Tsapara et al, 2010).…”

“…BVES forms a complex with ZO-1 and suppresses the GEF-H1-ZONAB pathway in corneal epithelial cells. It also regulates junctional integrity through aPKC, indicating that downregulation of BVES results in the modulation of several tight-junction-associated signalling pathways (Russ et al, 2010;Russ et al, 2011;Wu et al, 2012). However, the mechanism(s) underlying the tumour suppressor activity of BVES have not been identified.…”