SNAP to attention: A SNARE complex regulates neuronal progenitor polarity

SNARE vesicle targeting complex controls the polarity of neuronal progenitors. Kunii et al. (2020. J. Cell Biol. https://doi.org/10.1083/jcb.201910080) show that the SNAP23–VAMP8–Syntaxin1B complex is required for membrane targeting of N-cadherin and formation of adherence junction complexes in radial glia neuronal progenitors, the major prerequisite of cell polarity establishment.

Anatomical, Histochemical and Ultrastructural Adaptations of the Alimentary Canal of the Uromastyx aegyptius and the Spalerosophis diadema to their Food Habits

This study deals with anatomical, histochemical and ultrastructural adaptations of the alimentary canal of the Uromastyx aegyptius and the Spalerosophis diadema to their food habits. Proteins and nucleic acids are highly pronounced in the alimentary tract mucosal cells of the studied two species. A variable distribution of proteins and nucleic acids was observed in the different regions of the alimentary tract mucosa of the studied two species. The activity of alkaline phosphatase showed obvious variations not only among different organs, but also between the two species. At the ultrastructural level, the oesophageal mucosal cells contained oval shaped euchromatic nucleus with condensed chromatin and the perinuclear cytoplasm contained some electron-light vesicles. The gastric mucosal cells contained oval shaped euchromatic nucleus with condensed chromatin and the cytoplasm contained many rough endoplasmic reticulum, also many tonofilaments formed thick bundles which converged at the adherence junction in the lateral membranes. The small and large mucosal intestinal cells contained oval euchromatic nuclei and their cytoplasm contained few electron-light vesicles, also their lateral membranes showed many interdigitations. In spite of their difference in taxonomy, habitat, mode of feeding and their vital activities, they show more or less a similarity in the histochemical and ultrastructural patterns of their alimentary tract mucosa. This study can be applied to distinguish between different species of reptiles and for establishment of natural reserves.

Differential Targeting of the E-Cadherin/β-Catenin Complex by Gram-Positive Probiotic Lactobacilli Improves Epithelial Barrier Function

ABSTRACTThe intestinal ecosystem is balanced by dynamic interactions between resident and incoming microbes, the gastrointestinal barrier, and the mucosal immune system. However, in the context of inflammatory bowel diseases (IBD), where the integrity of the gastrointestinal barrier is compromised, resident microbes contribute to the development and perpetuation of inflammation and disease. Probiotic bacteria have been shown to exert beneficial effects, e.g., enhancing epithelial barrier integrity. However, the mechanisms underlying these beneficial effects are only poorly understood. Here, we comparatively investigated the effects of four probiotic lactobacilli, namely,Lactobacillus acidophilus,L. fermentum,L. gasseri, andL. rhamnosus, in a T84 cell epithelial barrier model. Results of DNA microarray experiments indicating that lactobacilli modulate the regulation of genes encoding in particular adherence junction proteins such as E-cadherin and β-catenin were confirmed by quantitative reverse transcription-PCR (qRT-PCR). Furthermore, we show that epithelial barrier function is modulated by Gram-positive probiotic lactobacilli via their effect on adherence junction protein expression and complex formation. In addition, incubation with lactobacilli differentially influences the phosphorylation of adherence junction proteins and the abundance of protein kinase C (PKC) isoforms such as PKCδ that thereby positively modulates epithelial barrier function. Further insight into the underlying molecular mechanisms triggered by these probiotics might also foster the development of novel strategies for the treatment of gastrointestinal diseases (e.g., IBD).

FXYD5 (dysadherin) regulates the paracellular permeability in cultured kidney collecting duct cells

FXYD5 (dysadherin or RIC) is a member of the FXYD family of single-span transmembrane proteins associated with the Na+-K+-ATPase. Several studies have demonstrated enhanced expression of FXYD5 during metastasis and effects on cell adhesion and motility. The current study examines effects of FXYD5 on the paracellular permeability in the mouse kidney collecting duct cell line M1. Expressing FXYD5 in these cells leads to a large decrease in amiloride-insensitive transepithelial electrical resistance as well as increased permeability to 4-kDa dextran. Impairment of cell-cell contact was also demonstrated by staining cells for the tight and adherence junction markers zonula occludens-1 and β-catenin, respectively. This is further supported by large expansions of the interstitial spaces, visualized in electron microscope images. Expressing FXYD5 in M1 cells resulted in a decrease in N-glycosylation of β1 Na+-K+-ATPase, while silencing it in H1299 cells had an opposite effect. This may provide a mechanism for the above effects, since normal glycosylation of β1 plays an important role in cell-cell contact formation (Vagin O, Tokhtaeva E, Sachs G. J Biol Chem 281: 39573–39587, 2006).