Pröls F, Mayer M P, Renner O, Czarnecki P G, Ast M, Gässler C, Wilting J, Kurz H, Christ B
Institute of Anatomy II, Albert-Ludwigs-University, Freiburg, 79104, Germany.
Exp Cell Res. 2001 Sep 10;269(1):42-53. doi: 10.1006/excr.2001.5294.
Angiogenesis research has focused on receptors and ligands mediating endothelial cell proliferation and migration. Little is known about the molecular mechanisms that are involved in converting endothelial cells from a proliferative to a differentiated state. Microvascular differentiation gene 1 (Mdg1) has been isolated from differentiating microvascular endothelial cells that had been cultured in collagen type I gels (3D culture). In adult human tissue Mdg1 is expressed in endothelial and epithelial cells. Sequence analysis of the full-length cDNA revealed that the N-terminal region of the putative Mdg1-protein exhibits a high sequence similarity to the J-domain of Hsp40 chaperones. We show that this region functions as a bona fide J-domain as it can replace the J-domain of Escherichia coli DnaJ-protein. Mdg1 is also upregulated in primary endothelial and mesangial cells when subjected to various stress stimuli. GFP-Mdg1 fusion constructs showed the Mdg1-protein to be localized within the cytoplasm under control conditions. Stress induces the translocation of Mdg1 into the nucleus, where it accumulates in nucleoli. Costaining with Hdj1, Hdj2, Hsp70, and Hsc70 revealed that Mdg1 colocalizes with Hsp70 and Hdj1 in control and stressed HeLa cells. These data suggest that Mdg1 is involved in the control of cell cycle arrest taking place during terminal cell differentiation and under stress conditions.
血管生成研究主要集中在介导内皮细胞增殖和迁移的受体及配体上。对于内皮细胞从增殖状态转变为分化状态所涉及的分子机制，我们了解甚少。微血管分化基因1（Mdg1）是从在I型胶原凝胶中培养的（三维培养）分化微血管内皮细胞中分离出来的。在成人组织中，Mdg1在内皮细胞和上皮细胞中表达。全长cDNA的序列分析表明，假定的Mdg1蛋白的N端区域与热休克蛋白40（Hsp40）伴侣蛋白的J结构域具有高度的序列相似性。我们发现该区域具有真正的J结构域功能，因为它可以替代大肠杆菌DnaJ蛋白的J结构域。当受到各种应激刺激时，原代内皮细胞和系膜细胞中的Mdg1也会上调。绿色荧光蛋白（GFP）-Mdg1融合构建体显示，在对照条件下，Mdg1蛋白定位于细胞质中。应激会诱导Mdg1转位至细胞核，并在核仁中积累。与Hdj1、Hdj2、Hsp70和Hsc70的共染色显示，在对照和应激的HeLa细胞中，Mdg1与Hsp70和Hdj1共定位。这些数据表明，Mdg1参与了终末细胞分化和应激条件下发生的细胞周期停滞的调控。
