Rab25 Deficiency Perturbs Epidermal Differentiation and Skin Barrier Function in Mice

Rab25, a member of the Rab11 small GTPase family, is central to achieving cellular polarity in epithelial tissues. Rab25 is highly expressed in epithelial cells of various tissues including breast, vagina, cervix, the gastrointestinal tract, and skin. Rab25 plays key roles in tumorigenesis, mainly by regulating epithelial differentiation and proliferation. However, its role in skin physiology is relatively unknown. In this study, we demonstrated that Rab25 knock-out (KO) mice show a skin barrier dysfunction with high trans-epidermal water loss and low cutaneous hydration. To examine this observation, we investigated the histology and epidermal differentiation markers of the skin in Rab25 KO mice. Rab25 KO increased cell proliferation at the basal layer of epidermis, whereas the supra-basal layer remained unaffected. Ceramide, which is a critical lipid component for skin barrier function, was not altered by Rab25 KO in its distribution or amount, as determined by immunohistochemistry. Notably, levels of epidermal differentiation markers, including loricrin, involucrin, and keratins (5, 14, 1, and 10) increased prominently in Rab25 KO mice. In line with this, depletion of Rab25 with single hairpin RNA increased the expression of differentiation markers in a human keratinocyte cell line, HaCaT. Transcriptomic analysis of the skin revealed increased expression of genes associated with skin development, epidermal development, and keratinocyte differentiation in Rab25 KO mice. Collectively, these results suggested that Rab25 is involved in the regulation of epidermal differentiation and proliferation.

Tumor associated proteins of rat skin tumor induced by 7,12-dimethylbenzaanthracene

The incidence of tumor and the time of expression, cellular localization and the molecular weight of tumor associated proteins of rat skin tumor induced by 7,12-dimethylbenz[a]anthracene (DMBA) with or without 12-O-tetradecanoyl-phorbol-13-acetate (TPA) were studied. The time of the development of skin tumors in 0.1% DMBA-TPA treated rats was significantly shorter than that in rats which were treated with DMBA alone. In the complete carcinogenesis case, papillomas developed more slowly and were less common and also squamous cell carcinomas appeared much later. From the analysis of the proteins of each experimental group by SDS-PAGE and two dimensional gel electrophoresis, at least three tumor associated proteins were identified (54kd, pl = 5.66; 27kd, pl = 5.85; 11kd, pl = 4.90). Also these proteins were found in rat dorsal skin from 14 days gestation to 21 days postpartum, and disappeared after 28 days. In conclusions, two stage skin carcinogenesis could be successfully demonstrated in Sprague-Dawley rats and abnormal proteins were produced in DMBA or DMBA-TPA induced skin tumor. The tumor associated proteins of skin tumor induced by DMBA or DMBA-TPA were appeared at the late initiation stage or early promotion stage, and they were localized in plasma membrane and were glycoproteins that are thought to be related to the epidermal differentiation process.

Tumor associated proteins of rat skin tumor induced by 7,12-dimethylbenzaanthracene

The incidence of tumor and the time of expression, cellular localization and the molecular weight of tumor associated proteins of rat skin tumor induced by 7,12-dimethylbenz[a]anthracene (DMBA) with or without 12-O-tetradecanoyl-phorbol-13-acetate (TPA) were studied. The time of the development of skin tumors in 0.1% DMBA-TPA treated rats was significantly shorter than that in rats which were treated with DMBA alone. In the complete carcinogenesis case, papillomas developed more slowly and were less common and also squamous cell carcinomas appeared much later. From the analysis of the proteins of each experimental group by SDS-PAGE and two dimensional gel electrophoresis, at least three tumor associated proteins were identified (54kd, pl = 5.66; 27kd, pl = 5.85; 11kd, pl = 4.90). Also these proteins were found in rat dorsal skin from 14 days gestation to 21 days postpartum, and disappeared after 28 days. In conclusions, two stage skin carcinogenesis could be successfully demonstrated in Sprague-Dawley rats and abnormal proteins were produced in DMBA or DMBA-TPA induced skin tumor. The tumor associated proteins of skin tumor induced by DMBA or DMBA-TPA were appeared at the late initiation stage or early promotion stage, and they were localized in plasma membrane and were glycoproteins that are thought to be related to the epidermal differentiation process.