Li Jingda, Yu Chengjie, Wang Renjun, Xu Jianrong, Chi Yan, Qin Jianzhong, Liu Qingping
Key Laboratory of Carbohydrate and Lipid Metabolism Research, College of Life Science and Technology, Dalian University, 10-Xuefu Avenue, Dalian Economical and Technological Development Zone, Liaoning 116622, China; School of Life Science and Biotechnology, Dalian University of Technology, Dalian 116024, Liaoning, China.
Key Laboratory of Carbohydrate and Lipid Metabolism Research, College of Life Science and Technology, Dalian University, 10-Xuefu Avenue, Dalian Economical and Technological Development Zone, Liaoning 116622, China.
Int J Biochem Cell Biol. 2017 Sep;90:121-135. doi: 10.1016/j.biocel.2017.07.022. Epub 2017 Aug 5.
CD36 signal transduction modulates the uptake of oxidized low-density lipoprotein (oxLDL) and foam cell formation. We previously observed that 7-ketocholesteryl-9-carboxynonanoate (oxLig-1), the lipid moiety of oxLDL, activates the CD36-Src-JNK/ERK1/2 signalling pathway. In this study, we assessed the role of the ω-carboxyl group in the binding of oxLig-1 to CD36 and investigated whether the binding of the ω-carboxyl group to CD36 triggers CD36-mediated signalling, thereby resulting in the upregulation of caveolin-1 expression. Our results showed that oxLig-1 bound to CD36 and that the ω-carboxyl group was critical for this binding. Furthermore, immunoprecipitation and Western blot analyses showed that interaction between the ω-carboxyl group of oxLig-1 and CD36 triggered intracellular Src-JNK/ERK1/2 signal transduction. Moreover, the binding of the ω-carboxyl group to CD36 induced caveolin-1 expression and translocation to the membrane in macrophages. Additionally, inhibitors of Src, JNK and ERK and siRNA targeting CD36 and NF-κB significantly suppressed the enhanced caveolin-1 expression induced by oxLig-1. In conclusion, these observations suggest that oxLig-1 is a critical epitope of oxLDL that mediates the binding of oxLDL to CD36 and activates downstream Src-JNK/ERK1/2-NF-κB signal transduction, resulting in upregulation of caveolin-1 expression in macrophages.
CD36信号转导调节氧化型低密度脂蛋白(oxLDL)的摄取及泡沫细胞形成。我们之前观察到,oxLDL的脂质部分7-酮胆固醇基-9-羧基壬酸酯(oxLig-1)可激活CD36-Src-JNK/ERK1/2信号通路。在本研究中,我们评估了ω-羧基在oxLig-1与CD36结合中的作用,并研究了ω-羧基与CD36的结合是否触发CD36介导的信号传导,从而导致小窝蛋白-1表达上调。我们的结果表明,oxLig-1与CD36结合,且ω-羧基对这种结合至关重要。此外,免疫沉淀和蛋白质印迹分析表明,oxLig-1的ω-羧基与CD36之间的相互作用触发了细胞内Src-JNK/ERK1/2信号转导。而且,ω-羧基与CD36的结合诱导了巨噬细胞中小窝蛋白-1的表达并使其转位至细胞膜。此外,Src、JNK和ERK的抑制剂以及靶向CD36和NF-κB的小干扰RNA(siRNA)显著抑制了oxLig-1诱导的小窝蛋白-1表达增强。总之,这些观察结果表明,oxLig-1是oxLDL的关键表位,介导oxLDL与CD36的结合并激活下游Src-JNK/ERK1/2-NF-κB信号转导,导致巨噬细胞中小窝蛋白-1表达上调。