Project description:Sphingosine 1-phosphate (S1P) is a bioactive lipid whose levels are tightly regulated by its synthesis and degradation. Intracellularly, S1P is dephosphoryled by the actions of two S1P-specific phosphatases, sphingosine 1-phosphate phosphatase 1 and 2. To identify the physiologic functions of S1P phosphatase 1, we have studied mice with its gene, Sgpp1, deleted. Sgpp1-/- mice appeared normal at birth but during the first week of life, they exhibited stunted growth, suffered desquamation, and most died before weaning. Interestingly, the epidermal permeability barrier developed normally during embryogenesis. Sgpp1 -/- pups and surviving adults exhibited epidermal hyperplasia and abnormal expression of keratinocyte differentiation markers. Keratinocytes isolated from Sgpp1 -/- skin had increased intracellular S1P levels, and expressed a gene expression profile that indicated enhanced differentiation. The results reveal S1P metabolism as a regulator of keratinocyte differentiation and epidermal homeostasis. Comparison of KO vs. WT with five replications per treatment sample
Project description:Sphingosine 1-phosphate (S1P) is a bioactive lipid whose levels are tightly regulated by its synthesis and degradation. Intracellularly, S1P is dephosphoryled by the actions of two S1P-specific phosphatases, sphingosine 1-phosphate phosphatase 1 and 2. To identify the physiologic functions of S1P phosphatase 1, we have studied mice with its gene, Sgpp1, deleted. Sgpp1-/- mice appeared normal at birth but during the first week of life, they exhibited stunted growth, suffered desquamation, and most died before weaning. Interestingly, the epidermal permeability barrier developed normally during embryogenesis. Sgpp1 -/- pups and surviving adults exhibited epidermal hyperplasia and abnormal expression of keratinocyte differentiation markers. Keratinocytes isolated from Sgpp1 -/- skin had increased intracellular S1P levels, and expressed a gene expression profile that indicated enhanced differentiation. The results reveal S1P metabolism as a regulator of keratinocyte differentiation and epidermal homeostasis.
Project description:Sphingosine-1-phosphate (S1P) is a sphingolipid metabolite that regulates basic cell functions through metabolic and signaling pathways. Intracellular metabolism of S1P is controlled, in part, by two homologous S1P phosphatases, 1 and 2, which are encoded by Sgpp1 and Sgpp2, respectively. S1P phosphatase activity is needed for efficient recycling of sphingosine into the sphingolipid synthesis pathway. S1P phosphatase 1 is important for skin homeostasis, but little is known about the functional role of S1P phosphatase 2. To identify the functions of S1P phosphatase 2 in vivo, we studied mice with the Sgpp2 gene deleted. In contrast to Sgpp1-/- mice, Sgpp2-/- mice had normal skin and were viable into adulthood. Unexpectedly, WT mice expressed Sgpp2 mRNA at high levels in pancreatic islets when compared with other tissues. Sgpp2-/- mice had normal blood insulin levels and pancreatic islet size; however, Sgpp2-/- mice treated with a high-fat diet (HFD) had significantly lower blood insulin levels and smaller pancreatic islets compared with WT mice. The smaller islets in the HFD-treated Sgpp2-/- mice had a significantly lower adaptive B-cell proliferation rate in response to the diet compared with HFD-treated WT mice. Importantly, B-cells from Sgpp2-/- mice fed a normal diet showed significantly increased expression of proteins characteristic of the endoplasmic reticulum (ER) stress response compared with B-cells from WT mice. Our results suggest that Sgpp2 deletion causes B-cell ER stress, which is a known cause of B-cell dysfunction, and reveal a novel juncture in the sphingolipid recycling pathway that could impact the development of diabetes. Three replications of Mouse (WT vs KO) that were treated with with Normal and HFD foods.
Project description:Progenitor cells at the basal layer of skin epidermis play an essential role in maintaining tissue homeostasis and enhancing wound repair in skin. The proliferation, differentiation, and cell death of epidermal progenitor cells have to be delicately regulated, as deregulation of this process can lead to many skin diseases, including skin cancers. However, the underlying molecular mechanisms involved in skin homeostasis remain poorly defined. In this study, with quantitative proteomics approach, we identified an important interaction between KDF1 (Keratinocyte Differentiation Factor 1) and IKKα (IκB kinase α) in differentiating skin keratinocytes. Ablation of either KDF1 or IKKα in mice leads to similar but striking abnormalities in skin development, particularly in skin epidermal differentiation. With biochemical and mouse genetics approach, we further demonstrate that the interaction of IKKα and KDF1 is essential for epidermal differentiation. To probe deeper into the mechanisms, we find that KDF1 associates with a deubiquitinating protease, USP7 (Ubiquitin Specific Peptidase 7), and KDF1 can regulate skin differentiation through deubiquitination and stabilization of IKKα. Taken together, our study unravels an important molecular mechanism underlying skin tissue homeostasis and epidermal differentiation.