Capo C, Meconi S, Sanguedolce M V, Bardin N, Flatau G, Boquet P, Mege J L
Unité des Rickettsies, Université de la Méditerranée, Centre National de la Recherche Scientifique, UPRESA 6020, Faculté de Médecine, Marseille, France.
J Immunol. 1998 Oct 15;161(8):4301-8.
Cytotoxic necrotizing factor-1 (CNF1) is isolated from pathogenic strains of Escherichia coli and catalyzes the activation of Rho GTPases by the deamidation of a glutamine residue. This toxin induces stress fiber formation, cell spreading, and membrane folding and promotes phagocytosis competence in epithelial cells. We show that CNF1 induces morphologic changes in monocytic cells: polarized-like shape in THP-1 cells, lamellipodia, and cell spreading in adherent monocytes. CNF1 also increased filamentous actin (F-actin) content in a time- and dose-dependent manner. In addition, the toxin profoundly reorganized the actin cytoskeleton: redistribution of F-actin in polarized deformations of THP-1 cells and disorganization of microfilament network in monocytes. We also studied the effects of CNF1 on phagocytosis. It markedly impaired the ingestion of unopsonized zymosan involving CR type 3. However, CNF1 had no effect on the uptake of iC3b-coated zymosan or IgG-mediated phagocytosis of SRBC. In addition, CNF1 induced clustering of CR3 and Fc gammaRII (CD32) but selectively impaired the colocalization of CR3 with F-actin. It is likely that CNF1-induced reorganization of actin cytoskeleton down-modulates integrin activation-dependent phagocytosis by preventing the codistribution of CR3 with F-actin. CNF1 may control some features of integrin-dependent phagocytosis in myeloid cells through its action on Rho GTP binding proteins and cytoskeletal organization.
细胞毒性坏死因子-1（CNF1）是从大肠杆菌致病菌株中分离出来的，它通过使谷氨酰胺残基脱酰胺作用来催化Rho GTP酶的激活。这种毒素可诱导应力纤维形成、细胞铺展和膜折叠，并促进上皮细胞的吞噬能力。我们发现CNF1可诱导单核细胞发生形态学变化：THP-1细胞呈极化样形态、出现片状伪足，贴壁单核细胞发生细胞铺展。CNF1还能以时间和剂量依赖的方式增加丝状肌动蛋白（F-肌动蛋白）的含量。此外，该毒素能深刻地重组肌动蛋白细胞骨架：在THP-1细胞的极化变形中F-肌动蛋白重新分布，单核细胞中的微丝网络紊乱。我们还研究了CNF1对吞噬作用的影响。它显著损害了未调理酵母聚糖（涉及CR3型）的摄取。然而，CNF1对iC3b包被的酵母聚糖的摄取或IgG介导的SRBC吞噬作用没有影响。此外，CNF1诱导CR3和FcγRII（CD32）聚集，但选择性地损害了CR3与F-肌动蛋白的共定位。很可能CNF1诱导的肌动蛋白细胞骨架重组通过阻止CR3与F-肌动蛋白的共分布来下调整合素激活依赖性吞噬作用。CNF1可能通过其对Rho GTP结合蛋白和细胞骨架组织的作用来控制髓样细胞中整合素依赖性吞噬作用的某些特征。
