Su M J, Bikle D D, Mancianti M L, Pillai S
Department of Medicine, University of California, San Francisco.
J Biol Chem. 1994 May 20;269(20):14723-9.
Extracellular calcium (Cao) stimulates the differentiation of keratinocytes; 1,25 dihydroxyvitamin D3 1,25(OH)2D3) does likewise. Since 1,25(OH)2D3 regulates calcium flux in other cells, we hypothesized that 1,25(OH)2D)3 acted through and promoted the effects of calcium on keratinocyte differentiation. To test this hypothesis, we evaluated the effects of calcium and 1,25(OH)2D3 alone and in combination on the mRNA and protein levels of involucrin and transglutaminase in neonatal human keratinocytes. Cao alone increased these mRNA levels in a dose-dependent fashion (0.03 to 1.2 mM) over a 24-h period. This increase in mRNA levels was associated with a stimulation by calcium of involucrin and transglutaminase gene transcription. However, by 72 h, the mRNA levels of involucrin and transglutaminase decreased. At 0.03 mM Cao, 1,25(OH)2D3 showed a dose-dependent stimulation of involucrin and transglutaminase mRNA for up to 48 h and potentiated the initial (4-h) stimulation by Cao of involucrin and transglutaminase mRNA. As for calcium alone, this increase in mRNA was associated with an increase in transcription of the involucrin and transglutaminase genes. However, by 24 h of exposure to both calcium and 1,25(OH)2D3, a dose-dependent fall in mRNA levels was seen. The mRNA levels of involucrin and transglutaminase were stable for 24 h when neonatal human keratinocytes were grown in serum-free keratinocyte growth medium containing 0.03 or 1.2 mM Cao alone. However, the mRNAs of both genes underwent rapid degradation when neonatal human keratinocytes were treated with 1,25(OH)2D3, especially in high Cao. 1,25(OH)2D3 and Cao increased the protein levels of involucrin and transglutaminase activity in a synergistic fashion throughout the 48-h time course. These data support the hypothesis that 1,25(OH)2D3 promotes calcium-induced differentiation at the level of both gene expression and mRNA stability.
细胞外钙（CaO）可刺激角质形成细胞的分化；1,25-二羟基维生素D3[1,25(OH)2D3]也有同样作用。由于1,25(OH)2D3可调节其他细胞中的钙通量，我们推测1,25(OH)2D3通过钙起作用并促进钙对角质形成细胞分化的影响。为验证这一假设，我们评估了单独及联合使用钙和1,25(OH)2D3对新生儿人角质形成细胞中兜甲蛋白和转谷氨酰胺酶的mRNA及蛋白水平的影响。单独的CaO在24小时内以剂量依赖方式（0.03至1.2 mM）增加了这些mRNA水平。mRNA水平的这种增加与钙对兜甲蛋白和转谷氨酰胺酶基因转录的刺激有关。然而，到72小时时，兜甲蛋白和转谷氨酰胺酶的mRNA水平下降。在0.03 mM CaO时，1,25(OH)2D3在长达48小时内对兜甲蛋白和转谷氨酰胺酶mRNA呈剂量依赖性刺激，并增强了CaO对兜甲蛋白和转谷氨酰胺酶mRNA的初始（4小时）刺激。与单独的钙一样，这种mRNA的增加与兜甲蛋白和转谷氨酰胺酶基因转录的增加有关。然而，在同时暴露于钙和1,25(OH)2D3 24小时后，观察到mRNA水平呈剂量依赖性下降。当新生儿人角质形成细胞在仅含有0.03或1.2 mM CaO的无血清角质形成细胞生长培养基中培养时，兜甲蛋白和转谷氨酰胺酶的mRNA水平在24小时内保持稳定。然而，当用1,25(OH)2D3处理新生儿人角质形成细胞时，尤其是在高CaO条件下，这两个基因的mRNA会迅速降解。在整个48小时的时间进程中，1,25(OH)2D3和CaO以协同方式增加了兜甲蛋白的蛋白水平和转谷氨酰胺酶活性。这些数据支持了1,25(OH)2D3在基因表达和mRNA稳定性水平上促进钙诱导分化的假设。
