Enteric commensal bacteria potentiate epithelial restitution via reactive oxygen species-mediated inactivation of focal adhesion kinase phosphatases

Abstract

The mechanisms by which enteric commensal microbiota influence maturation and repair of the epithelial barrier are relatively unknown. Epithelial restitution requires active cell migration, a process dependent on dynamic turnover of focal cell-matrix adhesions (FAs). Here, we demonstrate that natural, commensal bacteria stimulate generation of reactive oxygen species (ROS) in intestinal epithelia. Bacteria-mediated ROS generation induces oxidation of target cysteines in the redox-sensitive tyrosine phosphatases, LMW-PTP and SHP-2, which in turn results in increased phosphorylation of focal adhesion kinase (FAK), a key protein regulating the turnover of FAs. Accordingly, phosphorylation of FAK substrate proteins, focal adhesion formation, and cell migration are all significantly enhanced by bacterial contact in both in vitro and in vivo models of wound closure. These results suggest that commensal bacteria regulate cell migration via induced generation of ROS in epithelial cells.intestine | gastroenterology | phosphoprotein phosphatases | probiotics | lactobacillus T he mammalian gastrointestinal tract is home to an extraordinarily large group of commensal bacteria that mediate homeostatic effects on their host and influence a wide range of systemic metabolic, nutritional, and immune functions (1, 2). Additionally, the intestinal microbiota can directly affect the function of the epithelial cells that form a physical interface between the host and the luminal contents. For example, gut commensal bacteria have been implicated in regulation of epithelial proliferation, survival, barrier function, and resolution of epithelial wounds (3-6). In this report, we investigated the mechanisms by which the intestinal microbiota influence epithelial cell restitution.Epithelial cell restitution is a process during which wounds or breaks in the epithelial lining are repaired by migration of the surrounding epithelial cells. Cells at the leading edge flatten and move into the wounded area by rapidly extending lamellipodia, which are stabilized to the underlying matrix at specialized points called focal adhesions (FAs). The rapid disassembly of FAs at the rear end and assembly of FAs at the leading edge of the cells provides the traction force necessary for the cells to move forward (7). Additionally, FAs serve as signaling nidus points where multiple intracellular and extracellular signals integrate to coordinate cell migration. FAs are composed of protein complexes including transmembrane integrins, cytoplasmic signaling adaptors, and components of the actin cytoskeleton (8). A key regulatory protein of FA dynamics is focal adhesion kinase (FAK), a cytoplasmic tyrosine kinase that is phosphorylated in response to many extracellular signals. Models of cell migration demonstrate that phosphorylation of FAK and Src accompanies the formation of the FA complex, which subsequently mediates the turnover of adhesions and affects cell migration (7).Recently, we reported that commensal bacteria induce the generation of reactive oxygen s...

Mucosal Immunity and the Microbiome

“…We have shown that several species of normal human gut bacteria can induce rapid, "deliberate" generation of ROS within epithelial cells (23), and this ROS production has significant signaling effects on innate immunity, proliferation, and epithelial movement and restitution (19,29). Indeed, data in invertebrates suggest that ROS generation for signaling and microbiocidal functions in the gut epithelia may represent the ancestral form of response to bacteria (30).…”

“…In addition, individual members of the microbiota are able to actively modulate signaling intensity. A variety of reports have described commensals-many employed as probiotics-that are able to suppress eukaryotic inflammatory signaling pathways such as NF-kB and block inflammatory effector functions (19).…”

Exploring host–microbiota interactions in animal models and humans

“…The laboratory mouse has been instrumental for establishing roles for the gut microbiota in many aspects of mammalian physiology: angiogenesis (Stappenbeck et al 2002;Reinhardt et al 2012), bone mineral density (Cho et al 2012;Sjö gren et al 2012), brain development and behavior (Sudo et al 2004;Bravo et al 2011;Diaz Heijtz et al 2011;Ezenwa et al 2012), obesity and malnutrition Smith et al 2013), hepatic function (Dapito et al 2012;Henao-Mejia et al 2012), intestinal response to injury and repair (Rakoff-Nahoum et al 2004; Swanson et al 2011), and innate and adaptive immune function (for reviews, see Garrett et al 2010b;Littman and Pamer 2011;Hooper et al 2012). Ninety-nine percent of mouse genes are shared with humans at the host genetic level, and they share key similarities with the human gut microbiome at the phylum through family levels ( Fig.…”

Redox signaling mediated by the gut microbiota

“…Mass spectrometry analysis has revealed that redox-sensitive thiolates are present in a limited subset of enzymes. Examples include protein tyrosine phosphatases (PTP) [65], the lipid phosphatase (PTEN) [62,66], MAP kinase phosphatases (MAPKP) such as DUSP3 [63], and lowmolecular-weight protein tyrosine phosphatases (LMW-PTP) [67], in enzymes involved in the sumoylation and neddylation reactions, and well as in oxidant sensors such as Keap1, which control of overall redox balance of the cell. (Figure 1).…”