Retinoid effect on calcium, phospholipid-dependent protein kinase from mouse skin

Calcium, phospholipid-dependent protein kinase (C-kinase) was partially purified from skin of hairless mice. This enzyme activity was stimulated 6- to 15-fold in the presence of calcium and either diolein (DO), phosphatidyl serine (PS), or a mixture of the two. Tumor promoter, phorbol 12-myristate 13-acetate (PMA), also activated the enzyme either in the presence or in the absence of PS. beta-Carotene, retinol, retinal, retinoic acid, etretinate (trimethyl methoxyphenyl analog of retinoic acid), and isotretinoin (13-cis-retinoic acid) were tested for their effects on enzyme activity. Retinoic acid, etretinate, and isotretinoin stimulated enzyme activity in the absence of PS-DO, but inhibited PS-DO stimulated activity. The remaining compounds had no significant effect of C-kinase. In the presence of PS alone, these 3 retinoids had no effect on enzyme activity whereas retinoic acid and isotretinoin exhibited a dual effect of C-kinase in the presence of DO alone. Although the active retinoids seem to compete for binding sites on the enzyme with DO, the overall interaction among retinoids, DO, PS, and PMA appears to be more complex.