Pemphigus IgG Induces Expression of Urokinase Plasminogen Activator Receptor on the Cell Surface of Cultured Keratinocytes

Abstract

We previously found that the binding of pemphigus IgG to desmogleins caused marked activation of phospholipase C, a transient increase in inositol 1,4,5-trisphosphate production, and a concomitant increase in the intracellular calcium concentration in DJM-1 cells, a squamous cell carcinoma line. The binding of pemphigus IgG to cell membranes increased the activity of urokinase plasminogen activator in culture medium and induced subsequent cell-cell detachment in DJM-1 cells. Because urokinase plasminogen activator activates the conversion of plasminogen to plasmin by binding to urokinase plasminogen activator receptor evading inhibitors in serum, it is likely that plasmin is generated only in microenvironments adjacent to urokinase plasminogen activator receptor on the cell surface. It is not known whether pemphigus IgG causes acantholysis by inducing urokinase plasminogen activator receptor expression on the cell surface and secreting urokinase plasminogen activator in inhibitor-rich environments. We examined the effects of pemphigus IgG on urokinase plasminogen activator receptor expression in DJM-1 cells and normal keratinocytes by immunoblot analysis and immunofluorescence microscopy using antibodies to urokinase plasminogen activator receptor. IgG were obtained from serum samples from eight patients with bullous pemphigoid, five patients with pemphigus vulgaris, seven patients with pemphigus foliaceus, and eight normal subjects. Pemphigus vulgaris and pemphigus foliaceus IgG significantly increased the urokinase plasminogen activator receptor expression on the surface of DJM-1 cells and normal keratinocytes after 3- and 7-d incubation compared with normal IgG. These results suggest that enhanced urokinase plasminogen activator activity and urokinase plasminogen activator receptor expression activates plasmin in the limited cell surface of pemphigus IgG-bound keratinocytes and may contribute to the pathogenesis of differential acantholysis in pemphigus vulgaris and pemphigus foliaceus.

Further Support for a Role for Th2-like Cytokines in Blister Formation of Pemphigus

“…This contribution consists of several steps: an early T cell activation, which happens in draining lymph nodes, is required for cooperation with B lymphocytes and Ig isotype switching (11); later involvement of T helper lymphocytes (predominantly Th2, in our opinion) contributes to the amplification and automaintenance of the immune response because of T cell recruitment by chemotactic factors released by mast cells and keratinocytes. In this phase, cytokine production and profile play an important role; until now, there is no evidence that Th2-like cytokines could directly impair desmoglein function, but very recently (33,36) proteases have been thought to be responsible for the loss of adhesion between keratinocytes. In this view the epitope-specific Th2 response represents the triggering event for the recruitment and the involvement of the other cell types, as well as a large number of soluble factors and adhesion molecules, thus resulting in an inflammatory cascade of unequaled complexity.…”

150thAnniversary Series: Desmosomes and Autoimmune Disease, Perspective of Dynamic Desmosome Remodeling and Its Impairments in Pemphigus

“…The association of PKC α with desmosomal plaques accompanies the switch from hyper-adhesive to weak adhesive desmosomes during epidermal wound healing (Garrod et al, 2005). PVIgG, the principal antibody of which is anti-Dsg3, is also known to activate PKCs and is linked to cell -cell detachment events Seishima et al, 1997;Esaki et al, 1995). Thus, both intra-and extracellular Ca 2 ϩ concentrations and PKC are closely tied to the regulation of desmosome adhesive strength and assembly/disassembly.…”

Assembly Pathway of Desmoglein 3 to Desmosomes and Its Perturbation by Pemphigus Vulgaris-IgG in Cultured Keratinocytes, as Revealed by Time-Lapsed Labeling Immunoelectron Microscopy

“…Furthermore, because the internalized endosomes bearing half-desmosomes that are seen in Ca ϩϩ switch to low trypsin treatment, or in MDCK cells are morphologically similar to those seen in PV-IgG or PF-IgG treatment, it appears feasible that these responses to PV-or PF-IgG may be a result of, but not cause for, desmosomal splitting. It is also feasible that the activation of plasminogen activator and plasmin induced by PV-IgG binding (Hashimoto et al 1983;Morioka et al, 1981;Seishima et al, 1997) may be involved in desmosomal splitting and lead to internalization of half-desmosomes, even though this may not be a primary causative event in the blistering of pemphigus Mahoney et al, 1999). …”