JAM-A and aPKC: A close pair during cell-cell contact maturation and tight junction formation in epithelial cells

Osthole relieves skin damage and inhibits chronic itch through modulation of Akt/ZO-3 pathway in atopic dermatitis

Atopic dermatitis (AD) is the most prevalent chronic inflammatory skin condition and significantly reduces quality of life. Tight junction (TJ), which is located directly beneath the stratum corneum, maintains skin barrier function and aids in the identification of the cell's "territory". We evaluated seventeen TJ related genes to explore AD related alterations of TJ. Remarkably, we found that the expression of ZO-3, a gene that had not been linked to the development of TJ in AD, was significantly down-regulated in the skin of AD mice and patients. siRNA mediated knock-down of ZO-3 significantly decreased transepithelial electrical resistance in HaCaT cells, demonstrating that ZO-3 is essential to epidermal barrier function. In addition to ZO-3 downregulation, protein kinase B (Akt) phosphorylation was increased in the skin of AD mice. We further confirmed an inverse relationship between Akt phosphorylation and ZO-3 expression in AD using HaCaT cells and mouse model. Finally, we tested the efficacy of osthole as a treatment for AD in mice and HaCaT cells. Osthole inhibits Akt phosphorylation, and thereby enhances ZO-3 expression in mouse models of AD, resulting in greatly lessened AD associated skin damage and chronic itch, and osthole also increased the expression of ZO-3 in HaCaT cells by inhibiting the phosphorylation of Akt. Together, we established that ZO-3 is essential for the development of TJ in AD skin and HaCaT cells, and our findings provide fresh support for osthole's ability to protect ZO-3 expression and the epidermal barrier in AD.

Par3 promotes breast cancer invasion and migration through pull tension and protein nanoparticle-induced osmotic pressure

Cancer cell invasion and metastasis are closely related to intracellular tension. The cell-polarity protein, Par3, is a mechanical transmitter that affects cytoskeletal forces and determines breast cancer aggressiveness. Increased Par3 tension caused by aPKC inactivation is involved in filopodia and lamellipodia formation. Blocking the connection between Par3 and aPKC increases breast cancer aggressiveness both in vitro and in vivo. Meanwhile, aPKC-induced Par3 cytoplasmic translocation results in JAM-A phase separation and microfilament depolymerization, which is associated with increased intracellular protein nanoparticle-induced osmotic pressure. This study demonstrated the effects of aPKC on Par3 tension and osmotic pressure in breast cancer metastasis, and introduced Par3-associated mechanical mechanisms as potential targets for breast cancer treatment.

Epithelial adhesion molecules and the regulation of intestinal homeostasis during neutrophil transepithelial migration

Epithelial adhesion molecules play essential roles in regulating cellular function and maintaining mucosal tissue homeostasis. Some form epithelial junctional complexes to provide structural support for epithelial monolayers and act as a selectively permeable barrier separating luminal contents from the surrounding tissue. Others serve as docking structures for invading viruses and bacteria, while also regulating the immune response. They can either obstruct or serve as footholds for the immune cells recruited to mucosal surfaces. Currently, it is well appreciated that adhesion molecules collectively serve as environmental cue sensors and trigger signaling events to regulate epithelial function through their association with the cell cytoskeleton and various intracellular adapter proteins. Immune cells, particularly neutrophils (PMN) during transepithelial migration (TEM), can modulate adhesion molecule expression, conformation, and distribution, significantly impacting epithelial function and tissue homeostasis. This review discusses the roles of key intestinal epithelial adhesion molecules in regulating PMN trafficking and outlines the potential consequences on epithelial function.