Hemidesmosomes: how much plakins do they need?

Cell-Matrix Interactions Contribute to Barrier Function in Human Colon Organoids

The importance of cell-matrix adhesion to barrier control in the colon is unclear. The goals of the present study were to: (i) determine if disruption of colon epithelial cell interactions with the extracellular matrix alters permeability control measurement and (ii) determine if increasing the elaboration of protein components of cell-matrix adhesion complexes can mitigate the effects of cell-matrix disruption. Human colon organoids were interrogated for transepithelial electrical resistance (TEER) under control conditions and in the presence of Aquamin®, a multi-mineral product. A function-blocking antibody directed at the C-terminal region of the laminin α chain was used in parallel. The effects of Aquamin® on cell-matrix adhesion protein expression were determined in a proteomic screen and by Western blotting. Aquamin® increased the expression of multiple basement membrane, hemidesmosomal and focal adhesion proteins as well as keratin 8 and 18. TEER values were higher in the presence of Aquamin® than they were under control conditions. The blocking antibody reduced TEER values under both conditions but was most effective in the absence of Aquamin®, where expression of cell-matrix adhesion proteins was lower to begin with. These findings provide evidence that cell-matrix interactions contribute to barrier control in the colon.

Autoantibodies of non-inflammatory bullous pemphigoid hardly deplete type XVII collagen of keratinocytes

Type XVII collagen (COL17) and the non-collagenous 16A (NC16A) domain is regarded as the major pathogenic domains for bullous pemphigoid (BP). Some patients with BP have autoantibodies against parts of COL17 outside the NC16A domain (hereinafter the non-NC16A domain) and show less inflammatory manifestations. There were no significant differences in titres and IgG subclasses between NC16A-BP and non-NC16A-BP as determined by indirect immunofluorescent microscopy. The neutrophil activation capacities determined by ROS release did not differ between NC16A-BP and non-NC16A-BP. However, NC16A-BP IgG depleted COL17 in a dose-dependent manner. Treatment with NC16A-BP IgG, but not with non-NC16A-BP IgG, significantly decreased the adhesion strength. We speculate that the differences in clinical severity between NC16A-BP and non-NC16A-BP relate to the degree of COL17 depletion.

Complement-independent blistering mechanisms in bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease that clinically demonstrates tense blisters with widespread erythema, histologically demonstrates subepidermal blistering and immunologically demonstrates the presence of circulating autoantibodies against hemidesmosomal molecules. Complement activation has long been regarded as necessary for the generation of the BP. However, certain evidence has recently come to support non-complemental blistering mechanisms. The story of BP blistering mechanisms is a complicated one. This review mainly focuses on a specific blistering mechanism that highlights the role of complements in BP blistering.