Yonekura Hideto, Yamamoto Yasuhiko, Sakurai Shigeru, Petrova Ralica G, Abedin Md Joynal, Li Hui, Yasui Kiyoshi, Takeuchi Masayoshi, Makita Zenji, Takasawa Shin, Okamoto Hiroshi, Watanabe Takuo, Yamamoto Hiroshi
Department of Biochemistry and Molecular Vascular Biology, Kanazawa University Graduate School of Medical Science, Kanazawa 920-8640, Japan.
Biochem J. 2003 Mar 15;370(Pt 3):1097-109. doi: 10.1042/BJ20021371.
The binding of advanced glycation end-products (AGE) to the receptor for AGE (RAGE) is known to deteriorate various cell functions and is implicated in the pathogenesis of diabetic vascular complications. In the present study, we show that the cellular constituents of small vessels, endothelial cells (EC) and pericytes express novel splice variants of RAGE mRNA coding for the isoforms that lack the N-terminal V-type immunoglobulin-like domain (N-truncated) or the C-terminal transmembrane domain (C-truncated), as well as the known full-length mRNA. The ratio of the expression of the three variants was different between EC and pericytes; the content of the C-truncated form was highest in EC, whereas the full-length form was the most abundant in pericytes. Transfection experiments with COS-7 cells demonstrated that those variant mRNAs were translated into proteins as deduced; C-truncated RAGE was efficiently secreted into the culture media, and N-truncated RAGE was located mainly on the plasma membrane. The three isoforms were also detected in primary cultured human EC and pericytes. Further, full-length and C-truncated forms of RAGE bound to an AGE-conjugated column, whereas N-truncated RAGE did not. The AGE induction of extracellular-signal-related kinase phosphorylation and vascular endothelial growth factor in EC and of the growth and cord-like structure formation of EC was abolished completely by C-truncated RAGE, indicating that this endogenous secretory receptor (endogenous secretory RAGE) is cytoprotective against AGE. The results may contribute to our understanding of the molecular basis for the diversity of cellular responses to AGE and for individual variations in the susceptibility to diabetic vascular complications.
晚期糖基化终产物(AGE)与AGE受体(RAGE)的结合会使多种细胞功能恶化,并与糖尿病血管并发症的发病机制有关。在本研究中,我们发现小血管的细胞成分,即内皮细胞(EC)和平滑肌细胞表达了RAGE mRNA的新型剪接变体,这些变体编码的异构体缺乏N端V型免疫球蛋白样结构域(N端截短)或C端跨膜结构域(C端截短),以及已知的全长mRNA。EC和平滑肌细胞中这三种变体的表达比例不同;C端截短形式在EC中的含量最高,而全长形式在平滑肌细胞中最为丰富。用COS-7细胞进行的转染实验表明,这些变体mRNA如推断的那样被翻译成蛋白质;C端截短的RAGE被有效分泌到培养基中,而N端截短的RAGE主要位于质膜上。在原代培养的人EC和平滑肌细胞中也检测到了这三种异构体。此外,全长和C端截短形式的RAGE与AGE偶联柱结合,而N端截短的RAGE则不结合。C端截短的RAGE完全消除了EC中细胞外信号相关激酶磷酸化和血管内皮生长因子的AGE诱导,以及EC的生长和索状结构形成,表明这种内源性分泌受体(内源性分泌RAGE)对AGE具有细胞保护作用。这些结果可能有助于我们理解细胞对AGE反应多样性的分子基础以及糖尿病血管并发症易感性的个体差异。