Siegenthaler G, Saurat J H, Ponec M
Clinique de Dermatologie, Hôpital Cantonal Universitaire, Genève, Switzerland.
Exp Cell Res. 1988 Sep;178(1):114-26. doi: 10.1016/0014-4827(88)90383-7.
The control of normal epithelial cell growth and differentiation by retinoids (vitamin A and its analogs) may involve, at least in part, cellular retinoid-binding proteins. In the present study the levels of cellular retinoic acid (CRABP)- and retinol (CRBP)-binding proteins were measured in cultured normal human epidermal keratinocytes. To this end cells were cultured under either low calcium (nondifferentiating) or normal calcium (differentiating) conditions; in the latter culture the cells were also separated into nondifferentiated, attached cells, and differentiating, shed, cell populations. Two different techniques [gel filtration and polyacrylamide gel electrophoresis (PAGE)] were used, for both the qualitative and the quantitative determinations of retinoid-binding proteins. Gel filtration analysis on Sephadex G75 columns showed the presence of high-molecular-weight binding sites for retinol and retinoic acid in both nondifferentiated and the differentiating keratinocytes; the nature of these binding proteins is unclear. Free CRABP was found in the cytosol of differentiating cells, but was undetectable in nondifferentiated cells. Using a more sensitive PAGE technique, very low levels of CRABP and CRBP could be detected in nondifferentiated keratinocytes. By this technique it was possible to demonstrate very high levels of CRABP only in differentiating keratinocytes; the CRBP levels were found to be very low in differentiating cells and comparable to the amount found in nondifferentiated cells. On the basis of molecular weight determinations by gel exclusion and by electrophoretic mobility, the CRABP and CRBP of cultured keratinocytes were found to be identical to CRBP and CRABP from human epidermis.
类视黄醇（维生素A及其类似物）对正常上皮细胞生长和分化的调控可能至少部分涉及细胞类视黄醇结合蛋白。在本研究中，测定了培养的正常人表皮角质形成细胞中细胞视黄酸（CRABP）和视黄醇（CRBP）结合蛋白的水平。为此，将细胞在低钙（未分化）或正常钙（分化）条件下培养；在后者的培养中，细胞还被分离为未分化的贴壁细胞和分化的脱落细胞群体。使用两种不同的技术[凝胶过滤和聚丙烯酰胺凝胶电泳（PAGE）]来定性和定量测定类视黄醇结合蛋白。在Sephadex G75柱上进行的凝胶过滤分析表明，在未分化和分化的角质形成细胞中均存在视黄醇和视黄酸的高分子量结合位点；这些结合蛋白的性质尚不清楚。在分化细胞的细胞质中发现了游离的CRABP，但在未分化细胞中未检测到。使用更灵敏的PAGE技术，在未分化的角质形成细胞中可检测到极低水平的CRABP和CRBP。通过该技术，仅在分化的角质形成细胞中可证明CRABP水平非常高；发现分化细胞中的CRBP水平非常低，与未分化细胞中的含量相当。根据凝胶排阻和电泳迁移率测定的分子量，培养的角质形成细胞的CRABP和CRBP与人表皮的CRBP和CRABP相同。
