Paschen Stefan A, Christian Jan G, Vier Juliane, Schmidt Franziska, Walch Axel, Ojcius David M, Häcker Georg
Institute for Medical Microbiology, Immunology and Hygiene, Technische Universität München, D-81675 Munich, Germany.
J Cell Biol. 2008 Jul 14;182(1):117-27. doi: 10.1083/jcb.200804023.
Chlamydiae replicate in a vacuole within epithelial cells and commonly induce cell damage and a deleterious inflammatory response of unknown molecular pathogenesis. The chlamydial protease-like activity factor (CPAF) translocates from the vacuole to the cytosol, where it cleaves several cellular proteins. CPAF is synthesized as an inactive precursor that is processed and activated during infection. Here, we show that CPAF can be activated in uninfected cells by experimentally induced oligomerization, reminiscent of the activation mode of initiator caspases. CPAF activity induces proteolysis of cellular substrates including two novel targets, cyclin B1 and PARP, and indirectly results in the processing of pro-apoptotic BH3-only proteins. CPAF activation induces striking morphological changes in the cell and, later, cell death. Biochemical and ultrastructural analysis of the cell death pathway identify the mechanism of cell death as nonapoptotic. Active CPAF in uninfected human cells thus mimics many features of chlamydial infection, implicating CPAF as a major factor of chlamydial pathogenicity, Chlamydia-associated cell damage, and inflammation.
衣原体在上皮细胞内的液泡中复制，通常会导致细胞损伤以及引发分子发病机制不明的有害炎症反应。衣原体蛋白酶样活性因子（CPAF）从液泡转运至胞质溶胶，在那里它会切割多种细胞蛋白。CPAF最初以无活性前体的形式合成，在感染过程中经过加工并被激活。在此，我们表明，通过实验诱导寡聚化，CPAF可在未感染的细胞中被激活，这类似于起始半胱天冬酶的激活模式。CPAF活性会诱导细胞底物的蛋白水解，包括两个新的靶点，即细胞周期蛋白B1和聚（ADP-核糖）聚合酶（PARP），并间接导致仅含BH3结构域的促凋亡蛋白的加工。CPAF激活会在细胞中引发显著的形态变化，随后导致细胞死亡。对细胞死亡途径的生化和超微结构分析确定细胞死亡机制为非凋亡性。因此，未感染的人类细胞中的活性CPAF模拟了衣原体感染的许多特征，这表明CPAF是衣原体致病性、衣原体相关细胞损伤和炎症的主要因素。
