The Arp2/3 Inhibitory Protein Arpin Is Required for Intestinal Epithelial Barrier Integrity

Abstract

The intestinal epithelial barrier (IEB) depends on stable interepithelial protein complexes such as tight junctions (TJ), adherens junctions (AJ), and the actin cytoskeleton. During inflammation, the IEB is compromised due to TJ protein internalization and actin remodeling. An important actin regulator is the actin-related protein 2/3 (Arp2/3) complex, which induces actin branching. Activation of Arp2/3 by nucleation-promoting factors is required for the formation of epithelial monolayers, but little is known about the relevance of Arp2/3 inhibition and endogenous Arp2/3 inhibitory proteins for IEB regulation. We found that the recently identified Arp2/3 inhibitory protein arpin was strongly expressed in intestinal epithelial cells. Arpin expression decreased in response to tumor necrosis factor (TNF)α and interferon (IFN)γ treatment, whereas the expression of gadkin and protein interacting with protein C-kinase α-subunit 1 (PICK1), other Arp2/3 inhibitors, remained unchanged. Of note, arpin coprecipitated with the TJ proteins occludin and claudin-1 and the AJ protein E-cadherin. Arpin depletion altered the architecture of both AJ and TJ, increased actin filament content and actomyosin contractility, and significantly increased epithelial permeability, demonstrating that arpin is indeed required for maintaining IEB integrity. During experimental colitis in mice, arpin expression was also decreased. Analyzing colon tissues from ulcerative colitis patients by Western blot, we found different arpin levels with overall no significant changes. However, in acutely inflamed areas, arpin was significantly reduced compared to non-inflamed areas. Importantly, patients receiving mesalazine had significantly higher arpin levels than untreated patients. As arpin depletion (theoretically meaning more active Arp2/3) increased permeability, we wanted to know whether Arp2/3 inhibition would show the opposite. Indeed, the specific Arp2/3 inhibitor CK666 ameliorated TNFα/IFNγ-induced permeability in established Caco-2 monolayers by preventing TJ disruption. CK666 treatment also attenuated colitis development, colon tissue damage, TJ disruption, and permeability in dextran sulphate sodium (DSS)-treated mice. Our results demonstrate that loss of arpin triggers IEB dysfunction during inflammation and that low arpin levels can be considered a novel hallmark of acute inflammation.

HIV-1 diverts actin debranching mechanisms for particle assembly and release in CD4 T lymphocytes

“…Gag reaches a site where actin branching is lower and the assembly is easier at this location, or this could be induced by Gag recruiting a debranching factor to favor the assembly nucleation at that membrane location. Since CK666 is a debranched actin drug targeting directly the Arp2/3 complex, we hypothesis that Gag could hijack the Arp2/3 inhibitor Arpin to promote HIV-1 Gag assembly locally at the cell membrane as Arpin has been studied for the similarity of its function with the effect of CK666 (57, 58). Indeed, we found that Arpin membrane localization increased upon HIV-1 Gag expression in cells suggesting an interaction between Gag and Arpin that we revealed by an Arpin/Gag co-immunoprecipitation (Fig.…”

Phenotyping, genotyping, and prediction of abdominal pain in children using machine learning

“…ARPC5 and CLDN16 were significant genes related to the pathway, 'Tight junction', which may explain the characteristics of cluster 1. The intestinal epithelial barrier consists of interepithelial protein complexes, including tight junctions, adherens junctions, and the actin cytoskeleton [42]. ARPC5 protein is an important actin regulator responsible for actin cytoskeletal remodeling associated with compromised intestinal epithelium [42].…”

Theabrownin from Fu Brick Tea Improves Ulcerative Colitis by Shaping the Gut Microbiota and Modulating the Tryptophan Metabolism

“…3,4 As a crucial part of the intestinal mucosal barrier, the mechanical barrier is mainly composed of intestinal epithelial cells and tight junction (TJ) proteins between cells 5,6 whose damage will cause the pathogenic bacteria and endotoxin to migrate into extraintestinal tissues, activate the immune system, and aggravate the inflammatory response. 7,8 Gut microbiota is essential for protecting the gut from injury, 9,10 and generally a stable intestinal microbiota structure may prevent inflammation by resisting the colonization of pathogenic bacteria. 11 Besides, recent studies showed that gut microbiota-derived metabolites could dramatically affect the immune balance and maintain the intestinal mucosal integrity.…”

“…Recently, the global incidence of UC has been increasing yearly . Even though the precise etiology of UC is incompletely understood, the critical factor of the compromised gut barrier during UC pathogenesis has been highlighted by a large body of research. , As a crucial part of the intestinal mucosal barrier, the mechanical barrier is mainly composed of intestinal epithelial cells and tight junction (TJ) proteins between cells , whose damage will cause the pathogenic bacteria and endotoxin to migrate into extra-intestinal tissues, activate the immune system, and aggravate the inflammatory response. , …”