Ultraviolet B irradiation and activation of protein kinase D in primary mouse epidermal keratinocytes.
Our previous studies demonstrated that protein kinase D (PKD), a serine/threonine kinase implicated in various cell processes, is upregulated in basal cell carcinoma (BCC), supporting a possible tumorigenic role for PKD in skin. As the greatest risk factor for BCC is sun exposure, the ability of ultraviolet B (UVB) irradiation to activate PKD in primary mouse keratinocytes was investigated. Using western analysis with two autophosphorylation-specific antibodies, we show for the first time that UVB activated PKD in a time- and dose-dependent manner. UVB-induced PKD activation was verified using an in vitro kinase assay. Furthermore, activation was reduced by antioxidant pretreatment, suggesting a link with oxidative stress. UVB-induced PKD activation was mediated primarily by Src family tyrosine kinases rather than protein kinase C (PKC), and in fact, UVB did not alter PKC-mediated transphosphorylation. UVB induced apoptosis dose dependently, and this death could be prevented by overexpression of wild-type PKD, but not mutant PKD or the empty adenovirus. Indeed, a mutant that cannot be phosphorylated by Src kinases exacerbated UVB-elicited apoptosis. Thus, our data indicate that UVB irradiation of keratinocytes induces Src-mediated activation of PKD, which protects cells from UVB-stimulated apoptosis, providing a possible explanation for the observed upregulation of PKD in BCC.
Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA, USA.
S N
SN
Arun
I
I
Kaddour-Djebbar
B A
BA
Shapiro
W B
WB
Bollag
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D004789:Enzyme Activation; D000078404:Epidermal Cells; D015603:Keratinocytes / Q000201:enzymology / Q000528:radiation effects*; D051379:Mice; D010084:Oxidation-Reduction; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology*; D014466:Ultraviolet Rays / Q000009:adverse effects*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
C089212:protein kinase D; D019061:src-Family Kinases; D011493:Protein Kinase C