Tight junction-associated protein GEF-H1 in the neighbours of dividing epithelial cells is essential for adaptation of cell-cell membrane during cytokinesis

Simple graphical approach to investigate differences in transepithelial paracellular leak pathway permeability

Although many studies have reported differences in epithelial paracellular Leak Pathway permeability following genetic manipulations and treatment with various agents, the basis for these differences remains mostly unclear. Two primary mechanisms which could underlie differences in Leak Pathway permeability are differences in the density of Leak Pathway openings and differences in the opening size. Using a computational approach, we demonstrate that these two possibilities can be readily distinguished graphically by comparing the apparent paracellular permeabilities of a size panel of solutes measured across different cell layers. Using this approach, we demonstrated that depletion of ZO-1 protein in MDCK Type II renal epithelial cells decreased Leak Pathway opening size and increased opening density. Depletion of ZO-2 protein either had no effect or minimally decreased opening size and did not markedly change opening density. Comparison of MDCK Type II cells with MDCK Type I cells revealed that Type I cells exhibited a substantially smaller Leak Pathway permeability than did Type II cells. This lower permeability was due to a decrease in opening density with little or no change in opening size. These results demonstrate the utility of this approach to provide insights into the basis for observed differences in epithelial Leak Pathway permeability. This approach has wide applications including analysis of the molecular basis for Leak Pathway permeability, the effects of specific manipulations on Leak Pathway permeability properties, and the effects of permeation enhancers on Leak Pathway permeability properties.

Paxillin Promotes Breast Tumor Collective Cell Invasion through Maintenance of Adherens Junction Integrity

Distant organ metastasis is linked to poor prognosis during cancer progression. The expression level of the focal adhesion adapter protein paxillin varies among different human cancers, but its role in tumor progression is unclear. Herein, we utilize a newly generated PyMT mammary tumor mouse model with conditional paxillin ablation in breast tumor epithelial cells, combined with in vitro 3D tumor organoids invasion analysis and 2D calcium switch assays, to assess the roles for paxillin in breast tumor cell invasion. Paxillin had little effect on primary tumor initiation and growth but is critical for the formation of distant lung metastasis. In paxillin-depleted 3D tumor organoids, collective cell invasion was substantially perturbed. Two-dimensional cell culture revealed paxillin-dependent stabilization of adherens junctions (AJ). Mechanistically, paxillin is required for AJ assembly through facilitating E-cadherin endocytosis and recycling and HDAC6-mediated microtubule acetylation. Furthermore, Rho GTPase activity analysis and rescue experiments with a RhoA activator or Rac1 inhibitor suggest paxillin is potentially regulating the E-cadherin-dependent junction integrity and contractility through control of the balance of RhoA and Rac1 activities. Together, these data highlight new roles for paxillin in the regulation of cell-cell adhesion and collective tumor cell migration to promote the formation of distance organ metastases. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text].

Modeling blood-brain barrier pathology in cerebrovascular disease in vitro: current and future paradigms

The complexity of the blood-brain barrier (BBB) and neurovascular unit (NVU) was and still is a challenge to bridge. A highly selective, restrictive and dynamic barrier, formed at the interface of blood and brain, the BBB is a "gatekeeper" and guardian of brain homeostasis and it also acts as a "sensor" of pathological events in blood and brain. The majority of brain and cerebrovascular pathologies are associated with BBB dysfunction, where changes at the BBB can lead to or support disease development. Thus, an ultimate goal of BBB research is to develop competent and highly translational models to understand mechanisms of BBB/NVU pathology and enable discovery and development of therapeutic strategies to improve vascular health and for the efficient delivery of drugs. This review article focuses on the progress being made to model BBB injury in cerebrovascular diseases in vitro.