致病性原蟲陰道滴蟲細胞中F-actin capping protein之功能探討

Abstract

前人在定量蛋白質體學分析中發現陰道滴蟲的加帽蛋白 (F-actin capping protein，TvFACP) 在短時間加鐵刺激後，其表現量有明顯下降，在高等真核生物中FACP已知的主要功能為調控肌動蛋白聚合作用，並維持肌動蛋白絲 (Actin filament，F-actin) 的動態平衡。在本研究中利用免疫螢光染色觀察不同貼附力蟲株發現，Actin訊號在高貼附力陰道滴蟲的表現量較高，但表現量卻不受環境中鐵離子濃度影響。當在各種不同貼附力蟲株中過量表現TvFACP，雖無明顯改變其Actin表現量，但卻抑制其變形作用與基礎貼附能力。當進一步利用差速離心併合細胞分萃技術發現，當TvFACP過量表現於陰道滴蟲細胞時，會降低F-actin之聚合作用。最後以免疫沉澱法及GST沉降技術確認TvFACP與Actin的直接相互作用。綜合本研究結果顯示，在陰道滴蟲系統中TvFACP的功能可能是透過結合Actin而調控其F-actin聚合與細胞骨架重組，進而影響其變形作用與最終基礎貼附能力。

Trichomonas vaginalis colonized on the urogenital tract of human is the causative agent of world-spread trichomoniasis. In this parasite, the association of actin-based machinery in morphological transformation upon the process of adhesion and migration on host cells had been reported decades ago, but molecular mechanism remains unclear. In this study, the expression of an F-actin capping protein (TvFACP) and actin were detected to the level higher in those high-adherent clinical isolates and former was negatively regulated by environmental iron. By the transgenic system, TvFACP overexpression substantially impaired the efficiency of F-actin assembly, and also decreased both the morphological transformation population and adherence activity in the high-adherent isolates. On the other hand, TvFACP directly interacted with actin to form the protein complexes when examined by GST pull-down assay and immunoprecipitation. All data together, we speculated that TvFACP may act as an attenuator in dynamics of F-actin assembly in T. vaginalis. Iron presumably mediated expression of TvFACP with the activity binding to actin filaments, sequentially altering F-actin reorganization, morphological transformation and adherence of this parasite. The functional study of F-actin capping protein is a hot issue in the research society of high eukaryotes, and our findings may bring new ideas in the investigation of actin-mediated pathogenesis in T. vaginalis.