Abstract
Protein kinase D (PKD) is a family of stress-responsive serine/threonine kinases implicated in the regulation of diverse cellular functions including cell growth, differentiation, apoptosis, and cell motility. Although all three isoforms are expressed in keratinocytes, their role in skin biology and pathology is poorly understood. We recently identified a critical role for PKD1 during reversal of keratinocyte differentiation in culture, suggesting a potential proproliferative role in epidermal adaptive responses. Here, we generated mice with targeted deletion of PKD1 in the epidermis to evaluate the significance of PKD1 in normal and hyperplastic conditions. These mice displayed a normal skin phenotype, indicating that PKD1 is dispensable for skin development and homeostasis. Upon wounding, however, PKD1-deficient mice exhibited delayed wound re-epithelialization correlated with a reduced proliferation and migration of keratinocytes at the wound edge. In addition, the hyperplastic and inflammatory responses to topical phorbol ester were significantly suppressed, suggesting involvement of PKD1 in tumor promotion. Consistently, when subjected to the two-stage chemical skin carcinogenesis protocol, PKD1-deficient mice were resistant to papilloma formation when compared with control littermates. These results revealed a critical proproliferative role for PKD1 in epidermal adaptive responses, suggesting a potential therapeutic target in skin wound and cancer treatment.