The active Zot domain (aa 288–293) increases ZO‐1 and myosin 1C serine/threonine phosphorylation, alters interaction between ZO‐1 and its binding partners, and induces tight junction disassembly through proteinase activated receptor 2 activation

Abstract

Vibrio cholerae-derived zonula occludins toxin (Zot) is a multifunctional protein that reversibly disassembles intestinal tight junctions (tjs). Zot structure-function analysis has mapped this activity to aa 288-293, named AT1002. AT1002 reduced transepithelial electrical resistance across rat small intestine, ex vivo, as did Zot and its processed mature form, ΔG. AT1002 increased in vivo permeability to sugar tracers, whereas scrambled control peptides did not. Binding and barrier assays in proteinase activated receptor (PAR)(2)-expressing and PAR(2)-null cells established AT1002 activity to be PAR(2) dependent. Coincident with the increased intestinal permeability, confocal microscopy of AT1002-exposed rat intestinal IEC6 cells revealed displacement of ZO-1 and occludin from intercellular boundaries. In coimmunoprecipitation assays, AT1002 decreased ZO-1-occludin and ZO-1-claudin 1 interactions coincident with PKCα-dependent ZO-1 serine/threonine phosphorylation. Further, AT1002 increased serine phosphorylation of myosin 1C and, at the same time, transiently diminished its association with ZO-1. The COOH-terminal domain of ZO-1 was required for its association with myosin 1C. These data indicate that the NH(2)-terminal portion of active Zot contains a PAR(2)-activating motif, FCIGRL, that increases PKCα-dependent ZO-1 and myosin 1C serine/threonine phosphorylation. These modifications provoke selective disengagement of ZO-1 from its binding partners, occludin, claudin 1, and myosin 1C, coincident with opening of tjs.

The Blood-Testis Barrier and Its Implications for Male Contraception

“…It was also shown that phosphorylation of Tyr-398 and Tyr-402 prevents the interaction of occludin and ZO-1, dissociating the occludin-ZO-1 complex, thereby destabilizing the TJ barrier in colon carcinoma cell line (Caco-2), fibroblast cell line (Rat-1) or kidney cell lines (MDCK) (Elias et al, 2009). These findings are thus in agreement with other studies illustrating the significance of phosphorylation on the assembly of TJ proteins (e.g., occludin, claudin-5, ZO-1) into TJ fibrils at the TJ barrier in X. laevis oocytes (Cordenonsi et al, 1997(Cordenonsi et al, , 1999, small intestine (Goldblum et al, 2011), or brain endothelial cells (Yamamoto et al, 2008).…”

Zonulin as prehaptoglobin2 regulates lung permeability and activates the complement system

“…3A), which converted zonulin to HP2. As further support for the ability of zonulin to increase vascular permeability in mouse lung, we used AT-1002, which represents a peptide agonist of zonulin with permeability-inducing activity in the small intestine or in monolayers of intestinal epithelial cells (12). Similar to the application of AT-1001 in the previous experiments (Fig.…”

Role of Corticotropin-releasing Factor in Gastrointestinal Permeability

“…On the other hand, the tryptase released by mast cells upon activation has been shown to induce TJs disassembly through the activation of proteinase-activated receptor-2 of the epithelial cells. [88][89][90] These receptors can modulate enteric neurotransmission, secretion, motility, epithelial permeability, and visceral sensitivity, and are also known to regulate intestinal inflammation. 91 Anatomical contacts between mast cells and enteric nerve fibers have been demonstrated in the human gastrointestinal mucosa and inflammation multiplies these contacts.…”