The assembly of the major desmosome glycoproteins of Madin‐Darby canine kidney cells

Abstract

Madin-Darby canine kidney (MDCK) cells are unable to form desmosomes when cultured in low-calcium medium ([Caz+]<O.l meq./l), but can be induced to do so by raising the calcium to physiological concentrations (l-2 meq./l). We have previously demonstrated that this block correlated with increased desmosomal protein turnover. Here we have immunoprecipitated the major desmosome glycoproteins [DGI (150 kDa) and DGII/III (120/100 kDa)] from non-ionic detergent-soluble and -insoluble fractions prepared from metabolically labelled MDCK cells cultured in standard or lowcalcium medium. Pulse-chase studies showed that both DGI and DGII/III became unextractable in non-ionic detergent before their arrival at the cell surface, whether cells were grown in standard or low-calcium medium. The non-ionic detergent insolubility of these membrane components is therefore a separate step which precedes the formation of morphologically recognisable desmosomes.

The DSPII splice variant is critical for desmosome-mediated HaCaT keratinocyte adhesion

“…Previously published studies have shown that under low Ca 2+ conditions or conditions that prevent the formation of cell-cell contacts, the turnover of desmosomal proteins is high and they are rapidly degraded. However upon cell-cell contact these proteins are stabilised within the desmosome and their turnover decreases (as evidenced by less degradation) (Pasdar and Nelson, 1988;Penn et al, 1989;South, 2004). We therefore believe the changes we see in expression levels of other desmosomal components occur either at the post-translational level or because DSP is not present in levels sufficiently high to enable their stabilisation in junctions.…”

Structural and Functional Diversity of Desmosomes

“…This indicated that desmosomal plaque and membrane components did not form a preassembled intracellular complex before moving to cell contacts. Pasdar et al (1991) went on to demonstrate that newly synthesized desmoglein and desmoplakin transitioned over time from a soluble to insoluble pool, with respect to Triton X-100 extraction, a known trait of desmosomal components (Penn et al, 1989), regardless of cell contact. Equating insolubility with desmosome maturation, they concluded that desmoglein and desmoplakin acquired desmosome-like traits before desmosome formation, albeit at different rates.…”

The desmosome: cell science lessons from human diseases

“…Desmosome assembly and disassembly is thought to be a coordinated process in which the kinetics of synthesis and turnover of various components are tightly regulated (Gloushankova et al, 2003;Godsel et al, 2005;Mattey et al, 1990;Pasdar et al, 1991;Pasdar and Nelson, 1989;Penn et al, 1989;Windoffer et al, 2002). Cadherin endocytosis is an important mechanism for modulating cell adhesion during development and in certain epithelial-cell-derived tumors (Bryant and Stow, 2004;D'Souza-Schorey, 2005;Kowalczyk and Reynolds, 2004).…”