The type III secretion system effector EspO of enterohaemorrhagic Escherichia coli inhibits apoptosis through an interaction with HAX-1

MiR-483 targeting integrin β4 regulates the stability of intestinal barrier in turbot (Scophthalmus maximus) during pathogen infection

The hemidesmosome, critical for epithelial cell adhesion to the basement membrane, relies on integrin beta 4 (itgb4) as a central component. Mutations of Itgb4 caused intestinal epithelial cell exfoliation in mammals, highlighting its essential role in maintaining epithelial integrity. However, the distribution and function of itgb4 in fish intestines remain poorly understood. Fish intestines, unlike those of terrestrial animals, are constantly exposed to environmental pathogens such as Vibrio anguillarum, Edwardsiella piscicida, and Aeromonas salmonicida, which can cause significant intestinal epithelial cell exfoliation and compromise mucosal barrier function. Investigating the role of itgb4 in this context is crucial for developing strategies to prevent intestinal pathogen infections in aquaculture. This study analyzed the distribution, function, and expression of itgb4 during pathogenic infection in the intestines of Scophthalmus maximus (turbot). Results revealed that Itgb4 protein is predominantly localized in intestinal epithelial cells, particularly at the cell membrane, and its expression significantly decreased during early stages of pathogenic bacterial infection. Interfering with itgb4 led to severe exfoliation of intestinal epithelial cells, accompanied by the downregulation of adhesion-related proteins and upregulation of immune-related genes. In turbot intestinal cells, itgb4 interference increased cell migration, underscoring its critical role in maintaining stable cell adhesion. Furthermore, itgb4 knockdown in zebrafish weakened intestinal epithelial cell adhesion and altered skin epithelial morphology, demonstrating its broader role in epithelial integrity. Importantly, we identified miR-483 as a key regulator of itgb4 during pathogenic infection. miR-483 exhibited an expression pattern opposite to that of itgb4. Both in vitro and in vivo experiments confirmed its role in regulating intestinal epithelial cell exfoliation by targeting itgb4. This study reveals the critical role of itgb4 in maintaining fish intestinal epithelial adhesion and its regulation by miR-483, offering new insights for improving mucosal barrier function and disease resistance in aquaculture. These findings highlight itgb4 as a potential therapeutic target to enhance disease resistance in economically important fish species.

Systematic HOIP interactome profiling reveals critical roles of linear ubiquitination in tissue homeostasis

Linear ubiquitination catalyzed by HOIL-1-interacting protein (HOIP), the key component of the linear ubiquitination assembly complex, plays fundamental roles in tissue homeostasis by executing domain-specific regulatory functions. However, a proteome-wide analysis of the domain-specific interactome of HOIP across tissues is lacking. Here, we present a comprehensive mass spectrometry-based interactome profiling of four HOIP domains in nine mouse tissues. The interaction dataset provides a high-quality HOIP interactome resource with an average of approximately 90 interactors for each bait per tissue. HOIP tissue interactome presents a systematic understanding of linear ubiquitination functions in each tissue and also shows associations of tissue functions to genetic diseases. HOIP domain interactome characterizes a set of previously undefined linear ubiquitinated substrates and elucidates the cross-talk among HOIP domains in physiological and pathological processes. Moreover, we show that linear ubiquitination of Integrin-linked protein kinase (ILK) decreases focal adhesion formation and promotes the detachment of Shigella flexneri-infected cells. Meanwhile, Hoip deficiency decreases the linear ubiquitination of Smad ubiquitination regulatory factor 1 (SMURF1) and enhances its E3 activity, finally causing a reduced bone mass phenotype in mice. Overall, our work expands the knowledge of HOIP-interacting proteins and provides a platform for further discovery of linear ubiquitination functions in tissue homeostasis.

ZnO nanomaterials target mitochondrial apoptosis and mitochondrial autophagy pathways in cancer cells

In recent years, the application of engineering nanomaterials has significantly contributed to the development of various biomedical fields. Zinc oxide nanomaterials (ZnO NMts) have gained wide popularity due to their biocompatibility, unique physical and chemical properties, stability, and cost-effectiveness for large-scale production. They have emerged as potential materials for anticancer applications. This article provides a comprehensive review of the synthesis methods of ZnO NMts and highlights the advantages of combining ZnO NMts with anticancer drugs as a nano platform for cancer treatment. Additionally, the article briefly explains the mechanism of action of ZnO NMts in tumor cells, focusing on the mitochondrial pathways that target cell apoptosis and autophagy. It is observed that these pathways are primarily influenced by reactive oxygen species generated through oxidative stress. The article discusses the promising prospects of ZnO NMts combined with anticancer drugs in the field of cancer medicine and emphasizes the need for further in-depth research on the mitochondrial apoptosis and mitochondrial autophagy pathways.

Attaching and effacing pathogens modulate host mitochondrial structure and function

Enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) are human enteric pathogens that contribute significantly to morbidity and mortality worldwide. These extracellular pathogens attach intimately to intestinal epithelial cells and cause signature lesions by effacing the brush border microvilli, a property they share with other "attaching and effacing" (A/E) bacteria, including the murine pathogen Citrobacter rodentium. A/E pathogens use a specialized apparatus called a type III secretion system (T3SS) to deliver specific proteins directly into the host cytosol and modify host cell behavior. The T3SS is essential for colonization and pathogenesis, and mutants lacking this apparatus fail to cause disease. Thus, deciphering effector-induced host cell modifications is critical for understanding A/E bacterial pathogenesis. Several of the ∼20-45 effector proteins delivered into the host cell modify disparate mitochondrial properties, some via direct interactions with the mitochondria and/or mitochondrial proteins. In vitro studies have uncovered the mechanistic basis for the actions of some of these effectors, including their mitochondrial targeting, interaction partners, and consequent impacts on mitochondrial morphology, oxidative phosphorylation and ROS production, disruption of membrane potential, and intrinsic apoptosis. In vivo studies, mostly relying on the C. rodentium/mouse model, have been used to validate a subset of the in vitro observations; additionally, animal studies reveal broad changes to intestinal physiology that are likely accompanied by mitochondrial alterations, but the mechanistic underpinnings remain undefined. This chapter provides an overview of A/E pathogen-induced host alterations and pathogenesis, specifically focusing on mitochondria-targeted effects.

Impact of Epithelial Cell Shedding on Intestinal Homeostasis

The gut barrier acts as a first line of defense in the body, and plays a vital role in nutrition and immunoregulation. A layer of epithelial cells bound together via intercellular junction proteins maintains intestinal barrier integrity. Based on a tight equilibrium between cell extrusion and cell restitution, the renewal of the epithelium (epithelial turnover) permits the preservation of cell numbers. As the last step within the epithelial turnover, cell shedding occurs due to the pressure of cell division and migration from the base of the crypt. During this process, redistribution of tight junction proteins enables the sealing of the epithelial gap left by the extruded cell, and thereby maintains barrier function. Disturbance in cell shedding can create transient gaps (leaky gut) or cell accumulation in the epithelial layer. In fact, numerous studies have described the association between dysregulated cell shedding and infection, inflammation, and cancer; thus epithelial cell extrusion is considered a key defense mechanism. In the gastrointestinal tract, altered cell shedding has been observed in mouse models of intestinal inflammation and appears as a potential cause of barrier loss in human inflammatory bowel disease (IBD). Despite the relevance of this process, there are many unanswered questions regarding cell shedding. The investigation of those mechanisms controlling cell extrusion in the gut will definitely contribute to our understanding of intestinal homeostasis. In this review, we summarized the current knowledge about intestinal cell shedding under both physiological and pathological circumstances.