髓样分化蛋白-2在识别和转导内毒素信号中的作用

脂多糖(LPS)通过TLR4介导细胞炎症反应.研究表明,髓样分化蛋白-2(MD-2)通过与TLR4形成复合物参与LPS诱导的细胞信号过程.TLR4/MD-2复合物中的MD-2结合LPS后,引起TLR4低聚化,进而激发下游信号.MD-2合成后,大部分在内质网/高尔基体和TLR4结合,然后以TLR4/MD-2复合物的形式在细胞表面表达.这既能调节TLR4的胞内分布,又能辅助TLR4识别LPS.还有一部分MD-2释放到血浆中,形成可溶性的MD-2(sMD-2).sMD-2在CD14参与下,能结合血浆中的LPS,形成LPS-sMD-2复合物从而辅助只表达TLR4而不表达MD-2的细胞识别LPS,但过度表达的sMD-2又能抑制LPS信号.MD-2在TLR4介导的内毒素识别和信号转导过程中发挥了重要的调控作用.

The Role of MD-2 in The Process of Endotoxin Recognition and Signal Transduction

Lipopolysaccharide(LPS) can induce cell inflammation through interacting with TLR4. Recent studies have revealed that MD-2 participate in the process of LPS induced signal transduction pathway by forming a complex with TLR4. After binding to the MD-2 of the TLR4/MD-2 complex, LPS can induce TLR4- oligomerization and activate the downstream signal pathway. After being synthesized, most MD-2 can bind to TLR4 at the endoplasmic reticulum /Golgi apparatus and expresse as TLR4/MD-2 complex at the cellular surface. Therefore MD-2 not only can regulate the distribution of TLR4 in the cytoplasm, but also help TLR4 to recognize LPS. Another part of MD-2 can be released into plasma as soluble MD-2(sMD-2). With the help of CD14, sMD-2 would interact with LPS in the plasma to constitute LPS-sMD-2 complex, helping cell who express only TLR4, to recognize LPS, however excessive expressed sMD-2 would repress the LPS signal transduction pathway. In conclusion, MD-2 plays a crucially modulating role in the process of TLR4 mediated endotoxin recognition and signal transduction.