The Effects of Calcium and Retinoic Acid on Epidermal Desmosomes

Kim, Soo Chan; Won, Jin Hyoung

Abstract

BACKGROUND: Desmosomes are adhesive intercellular junctions that form an important component of the junction complexes of epithelial cells. They provide intercellular links between the intermediate filament cytoskeletons of adjacent cells and are thus involved in maintaining the structural integrity of tissues.
OBJECTIVE
Calcium and retinoids are major regulators of epidermal differentiation and their role on keratin proteins are well known. However, their effects on desmosome moleucles are unknown. To address this question we initiated a study of the effects of these epidermal differentiation regulators on desmosomal components, i.e., desmoplakin, desmoglein, and pemphigus antigens.
METHODS
We used monoclonal antibodies against desmoplakin(DP) and desmoglein(DG), and sera from patients with pemphigus vulgaris(PV), pemphigus foliaceus(PF) and paraneoplastic pemphigus (PNP) to study the effects of calcium and retinoic acids, which are major regulators of epidermal differentation, on desmosomal protein formation in human cultured deratinocytes. We performed immunofluorescence, immunoblotting and immunoprecipitation study using human keratinocytes cultured in high calcium media with or without retinoic acid and in low calcium media with or without retinoic acid.
RESULTS
1. In low calcium (0.15mM) media, PV antigen and DG were produced in a small amount and it appeared that these desmosomal proteins were located in cytosol. Whereas in high calcium (1.8mM) media, production of these desmosomal proteins was increased not they were assembled at the desmosomal structures located in cell-cell contact margins. 2. PF antigen, which was identical to the DG, were not produced or expressed in cultured keratinocytes even when cultured in high calcium media. 3. PNP antigen and DP were produced in cultured keratinocytes grown in both high low calcium media but their production was increased in high calcium media and only in high calcium media they were assembled at the desmosomal structures. 4. Retinoic acids induced loosening of cell-cell contacts of cultured keratinocytes and decreased the production of desmosomal proteins.
CONCLUSION
Our results suggests calcium is a major regulator of the production and assembly of desmosomal proteins including pemphigus antigens, but PF sera and monoclonal antibodies against DG show different antigen binding characteristics. It appears that retinoic acids inhibit production of desmosomal proteins.