Distribution of the tight junction proteins ZO-1, occludin, and claudin-4, -8, and -12 in bladder epithelium

Abstract

In mammals, the bladder stores urine without permitting the passage of urine contents into the bloodstream, a function, in part, of the uroepithelial-associated tight junction complex. The protein constituents that make up this high-resistance barrier in the bladder are currently unknown, although the claudins, a multigene family, are thought to govern paracellular transport in other epithelia. Reverse transcriptase-polymerase chain reaction analysis was used to define that mRNA for claudin-2, -4, -8, -12, and -13 was expressed in mouse bladder tissue. The localization of these claudins, as well as the tight junction-associated proteins zonula occludens-1 (ZO-1) and occludin, within the bladder epithelium was determined by immunofluorescence microscopy. As expected, occludin and ZO-1 were localized to the tight junctions of rat, mouse, and rabbit umbrella cells. Intriguingly, ZO-1 in mouse epithelium, ZO-1 in the dome region of rabbit bladders and occludin in rat and mouse bladders were also expressed in the underlying intermediate and basal cell layers. Claudin-4, -8, and -12 were found in the umbrella cell tight junction; however, additional staining of claudin-4 was observed along the sites of cell-cell contact in the underlying cell layers of rat, mouse, and rabbit tissue. No claudin-2 staining was associated with tight junctions in the uroepithelium. Our results indicate that claudin-4, -8, and -12 are expressed in umbrella cells, where they may impart the high-resistance phenotype associated with this cell type, and that in some instances tight junction proteins are also associated at the sites of cell contact of the underlying cell layers, perhaps playing some role in cell-cell adhesion.

PPARγ‐regulated tight junction development during human urothelial cytodifferentiation

“…In addition, our study presents evidence that urothelium in situ expresses claudins 1, 2, 8 and 10, at least at the mRNA level. Our results extend previous studies that have demonstrated expression of ZO1 by human urothelia and ZO1, occludin and claudins 4, 8, 12 by rodent urothelia (Acharya et al, 2004;Slobodov et al, 2004).A majority of TJ proteins were not restricted to the 'kissing points' of the terminal junctions between the superficial cells. Indeed, several component proteins were expressed in basal and intermediate cell zones, although localisation at intercellular sites occurred primarily in the upper intermediate and superficial cell zones.…”

“…Indeed, several component proteins were expressed in basal and intermediate cell zones, although localisation at intercellular sites occurred primarily in the upper intermediate and superficial cell zones. This phenomenon has been observed previously in other epithelial tissues and implies that the claudins may have extended roles in regulating paracellular permeability within stratified tissues, although an alternative role in cell adhesion has also been suggested (Gregory et al, 2001;Langbein et al, 2002;Mysorekar et al, 2002;Acharya et al, 2004).Our immunohistochemical results indicate a coordinated pattern of TJ-associated protein expression relating to differentiation stage in situ (Fig. 1B): claudins 4 and 5 are expressed at a later stage of differentiation than claudin 7 and occludin, but prior to claudin 3, which, together with ZO1, is implicated in the terminal junction of the superficial cells.…”

“…However, very little is known of the composition of the urothelial TJ, which is responsible for maintaining the paracellular barrier. Although urothelium is regarded as one of the 'tightest' of all epithelia, there has been very little work on TJ composition in man (Slobodov et al, 2004) or other species (Acharya et al, 2004).The morphology of the urothelium and the expression of AUM plaques by the superficial cells imply a differentiation-associated acquisition of barrier function. In order to address this issue, we have exploited our well established in vitro model of normal human urothelial (NHU) cells (Southgate et al, 1994(Southgate et al, , 2002, using pharmacological activation of peroxisome proliferator activated receptor γ (PPARγ) to induce urothelial cytodifferentiation (Varley et al, 2004a,b).…”

Distinct Apical and Basolateral Membrane Requirements for Stretch-induced Membrane Traffic at the Apical Surface of Bladder Umbrella Cells

“…The increase may represent a slowing in the endocytic rate or an increase in exocytic rate. Additional mechanosensors may include the actomyosin cytoskeleton, which in conjunction with integrins is required for mechanosensation in both anchored and nonanchored cells (Gillespie and Walker, 2001;Frey et al, 2006;Ingber, 2006;Effler et al, 2007) and is prominently associated with the basolateral membrane of the umbrella cell (Acharya et al, 2004). Treatment with cytochalasin D or latrunculin impairs exocytosis and endocytosis in umbrella cells (Lewis and de Moura, 1982).…”

Expression of Coxsackievirus and Adenovirus Receptor Isoforms in Developing Mouse Bladder Uroepithelium

“…[3][4][5] To date, several different TJ proteins have been identified in the bladder uroepithelium. [6][7][8][9] One such TJ protein is coxsackievirus and adenovirus receptor (CAR), a member of the Ig-type superfamily of cell adhesion molecules. CAR in the epithelial lining plays a role in the regulation of epithelial permeability.…”