Regulation of protein kinase D during differentiation and proliferation of primary mouse keratinocytes.
Diseased skin often exhibits a deregulated program of the keratinocyte maturation necessary for epidermal stratification and function. Protein kinase D (PKD), a serine/threonine kinase, is expressed in proliferating keratinocytes, and PKD activation occurs in response to mitogen stimulation in other cell types. We have proposed that PKD functions as a pro-proliferative and/or anti-differentiative signal in keratinocytes and hypothesized that differentiation inducers will downmodulate PKD to allow differentiation to proceed. Thus, changes in PKD levels, autophosphorylation, and activity were analyzed upon stimulation of differentiation and proliferation in primary mouse keratinocytes. Elevated extracellular calcium and acute 12-O-tetradecanoylphorbol-13-acetate (TPA) treatments induced differentiation and triggered a downmodulation of PKD levels, autophosphorylation at serine 916, and activity. Chronic TPA treatment stimulated proliferation and resulted in a recovery of PKD levels, autophosphorylation, and activity. Immunohistochemical analysis demonstrated PKD localization predominantly in the proliferative basal layer of mouse epidermis. Co-expression studies revealed a pro-proliferative, anti-differentiative effect of PKD on keratinocyte maturation as monitored by increased and decreased promoter activities of keratin 5, a proliferative marker, and involucrin, a differentiative marker, respectively. This work describes the inverse regulation of PKD during keratinocyte differentiation and proliferation and the pro-proliferative/anti-differentiative effects of PKD co-expression on keratinocyte maturation.
Ernest Dodd
M
M
Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912, USA.
Ristich
Vladimir L
VL
Ray
Sagarika
S
Lober
Robert M
RM
Bollag
Wendy B
WB
D000818:Animals; D000831:Animals, Newborn; D000918:Antibody Specificity; D019556:COS Cells; D002117:Calcitriol / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002273:Carcinogens / Q000494:pharmacology; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002522:Chlorocebus aethiops; D005110:Extracellular Space / Q000187:drug effects; D053569:Keratin-15; D053555:Keratin-5; D015603:Keratinocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D007633:Keratins / Q000235:genetics; D051379:Mice; D008813:Mice, Inbred ICR; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000502:physiology; D011493:Protein Kinase C / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011498:Protein Precursors / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D011503:Transglutaminases / Q000378:metabolism
D002120:Calcium Channel Agonists; D002273:Carcinogens; D053569:Keratin-15; D053555:Keratin-5; C492053:Krt15 protein, mouse; D011498:Protein Precursors; C032253:involucrin; D007633:Keratins; D011503:Transglutaminases; C089212:protein kinase D; D011493:Protein Kinase C; D002117:Calcitriol; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium