Nonmuscle Myosin IIA Regulates Intestinal Epithelial Barrier in vivo and Plays a Protective Role During Experimental Colitis

Abstract

The actin cytoskeleton is a critical regulator of intestinal mucosal barrier permeability, and the integrity of epithelial adherens junctions (AJ) and tight junctions (TJ). Non muscle myosin II (NM II) is a key cytoskeletal motor that controls actin filament architecture and dynamics. While NM II has been implicated in the regulation of epithelial junctions in vitro, little is known about its roles in the intestinal mucosa in vivo. In this study, we generated a mouse model with an intestinal epithelial-specific knockout of NM IIA heavy chain (NM IIA cKO) and examined the structure and function of normal gut barrier, and the development of experimental colitis in these animals. Unchallenged NM IIA cKO mice showed increased intestinal permeability and altered expression/localization of several AJ/TJ proteins. They did not develop spontaneous colitis, but demonstrated signs of a low-scale mucosal inflammation manifested by prolapses, lymphoid aggregates, increased cytokine expression, and neutrophil infiltration in the gut. NM IIA cKO animals were characterized by a more severe disruption of the gut barrier and exaggerated mucosal injury during experimentally-induced colitis. Our study provides the first evidence that NM IIA plays important roles in establishing normal intestinal barrier, and protection from mucosal inflammation in vivo.

Cell Biology of Tight Junction Barrier Regulation and Mucosal Disease

“…Some investigators have argued that, because MLCK could, theoretically, phosphorylate substrates other than myosin II regulatory light chain, a more appropriate study would be to analyze mice lacking nonmuscle myosin IIA heavy chain specifically within the intestinal epithelium (Naydenov et al 2016). However, these tissue-specific nonmuscle myosin IIA heavy chain-deficient mice display barrier defects and intestinal disease under basal (i.e., unstressed) conditions.…”

Inflammation and the Intestinal Barrier: Leukocyte–Epithelial Cell Interactions, Cell Junction Remodeling, and Mucosal Repair

“…98 Both inhibition and activation of NM II disrupts the epithelial barrier and triggers AJ and TJ disassembly. 99–101 Likewise, recent studies using knockout and transgenic mouse models revealed that both the inhibition of the actin motor, via the intestinal epithelial-specific knockout of NM IIA, 102 and overactivation of NM II, via the overexpression of constitutively active MLCK in the intestinal epithelium, 103 resulted in increased intestinal permeability. These findings suggest that balanced NM II activity controls integrity of the gut barrier.…”

Endoplasmic reticulum chaperone Gp96 controls actomyosin dynamics and protects against pore‐forming toxins

“…Pathogenic Escherichia coli can target Gp96 to promote nitric oxide production, Ca 2+ oscillations and activation of cellular kinases such as PKC-a and FAK, which disrupts endothelial cell junctions and mediates bacterial internalization [40]. LLO and other PFTs trigger such events, which were associated with increased tissue damage in vivo [41,42], and NMHCIIA protects the epithelial barrier in vivo [43]. Interestingly, Lm can interact with Gp96 via its surface protein Vip, which promotes bacterial internalization [18].…”