Identification of a protein (s) that interacts with Fas igand.

Fas配体(Fas Ligand，FasL)是肿瘤坏死因子家族的II型膜蛋白，通过与其受体Fas结合来诱导细胞凋亡。金属蛋白酶裂解结合在膜上的FasL，产生其可溶形式。为了确定哪种形式的FasL诱导细胞凋亡，我们制备了可溶性的重组FasL，并建立了表达不可切割的膜结合FasL的转化细胞系。膜结合型FasL对小鼠肝细胞和人Jurkat细胞均有杀伤作用，但不能被可溶性FasL杀伤，提示膜结合型FasL是效应分子，其脱落后的裂解作用是下调其功能。已知的肿瘤坏死因子被TACE(肿瘤坏死因子α转换酶)所切割。TACE生化分析表明，TACE与肿瘤坏死因子在同一细胞中表达，且不切割FasL。将表达FasL的肿瘤细胞移植到小鼠的腹膜后，通过募集中性粒细胞引起炎症反应。因此，当腹膜腔细胞与Fas L孵育时，它们在发生凋亡的同时产生IL-1β。这些结果表明，凋亡细胞招募炎性细胞来清理军团。

Fas ligand (FasL) is a type II membrane protein belonging to the tumor necrosis factor (TNF) family, and induces apoptosis by binding its receptor Fas. A metalloproteinase cleaves the membrane-bound FasL, to produce its soluble form. To determine which forms of FasL, the membrane-bound or soluble form induces apoptosis, we prepared the soluble recombinant FasL and also established transformant cell lines that express non-cleavable membrane-bound FasL. Mouse hepatocytes and human Jurkat cells were killed by the membrane-bound FasL, butnot by soluble FasL, indicating that the membrane-bound form of FasL is the effector molecule, and its cleavage by shedding is to down-regulate the function. TNF is known to be cleaved by TACE (TNF alpha converting enzyme). Biochemical analysis of TACE indicated that TACE should be expressed in the same cells as TNF, and it does not cleave FasL. When the tumor cells expressing FasL are transplanted to peritoneal cavity of mice, it caused inflammation by recruiting neutrophils. Accordingly, when cells from the peritoneal cavity are incubated with FasL, they produced IL-1β while undergoing apoptosis. These results suggested that the apoptotic cells recruit inflammatory cells to clean up the corps.