THE EXPRESSION OF DESMOGLEIN ISOFORMS IN CULTURED HUMAN KERATINOCYTESIS REGULATED BY CALCIUM, SERUM, AND PROTEIN-KINASE-C

Three desmoglein (Dsg) isoforms are expressed in a differentiation-spe cific fashion in the epidermis, with Dsg2 being basal, Dsg3 (pemphigus vulgaris antigen) basal and spinous, and Dsg1 (pemphigus foliaceus an tigen) predominately granular. To better understand the mechanism(s) r egulating Dsg isoform expression, we examined the expression pattern o f Dsg1, Dsg2, and Dsg3 in normal human epidermal keratinocytes (NHEKs) , the immortalized, nontumorigenic HaCaT cell Line, and several squamo us cell carcinoma cell lines (SCC-9, SCC-12F, SCC-13, and SCC-25). In all cells, the accumulation of high Dsg protein levels required calciu m and was not observed in low calcium (0.05-0.07 mM) media. NHEKs expr essed Dsg1 in all media tested, consistent with their normal different iation capacity. HaCaT and SCC-25 also expressed Dsg1; however, the pr esence of serum in the media dramatically decreased Dsg1 protein level s. Serum also inhibited Dsg1 mRNA levels in HaCaT cells. Dsg1 was not detected in extracts from SCC-B, SCC-12F, and SCC-13 under any conditi ons. Since activation of protein kinase C (PKC) is involved in keratin ocyte differentiation, we evaluated the effects of PKC down-regulation on Dsg isoform expression. Long-term treatment with either the phorbo l ester 12-O-tetradecanoylphorbol-13-acetate (TPA) or bryostatin 1 inh ibited levels of Dsg1 and Dsg3, but not Dsg2 in NHEKs and HaCaT cells. Chronic TPA also decreased Dsgl and Dsg3 mRNA levels in NHEKs, furthe r supporting a role for PKC activation in the expression of the suprab asal Dsg1 and Dsg3. These results identify several regulatory mechanis ms by which the differentiation-specific pattern of desmosomal cadheri ns is established in the epidermis. (C) 1998 Academic Press.