Exploitation of the endocytic pathway by Orientia tsutsugamushi in nonprofessional phagocytes.
Orientia tsutsugamushi, a causative agent of scrub typhus, is an obligate intracellular bacterium that requires the exploitation of the endocytic pathway in the host cell. We observed the localization of O. tsutsugamushi with clathrin or adaptor protein 2 within 30 min after the infection of nonprofessional phagocytes. We have further confirmed that the infectivity of O. tsutsugamushi is significantly reduced by drugs that block clathrin-mediated endocytosis but not by filipin III, an inhibitor that blocks caveola-mediated endocytosis. In the present study, with a confocal microscope, O. tsutsugamushi was sequentially colocalized with the early and late endosomal markers EEA1 and LAMP2, respectively, within 1 h after infection. The colocalization of O. tsutsugamushi organisms with EEA1 and LAMP2 gradually disappeared until 2 h postinfection, and then free O. tsutsugamushi organisms were found in the cytoplasm. When the acidification of endocytic vesicles was blocked by treating the cells with NH(4)Cl or bafilomycin A, the escape of O. tsutsugamushi organisms from the endocytic pathway was severely impaired, and the infectivity of O. tsutsugamushi was drastically reduced. To our knowledge, this is the first report that the invasion of O. tsutsugamushi is dependent on the clathrin-dependent endocytic pathway and the acidification process of the endocytic vesicles in nonprofessional phagocytes.
Chu
Hyuk
H
Department of Microbiology and Immunology, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Republic of Korea.
Lee
Jung-Hee
JH
Han
Seung-Hoon
SH
Kim
Se-Yoon
SY
Cho
Nam-Hyuk
NH
Kim
Ik-Sang
IS
Choi
Myung-Sik
MS
D000818:Animals; D002460:Cell Line; D002461:Cell Line, Transformed; D002966:Clathrin / Q000502:physiology; D004705:Endocytosis / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000382:microbiology; D005347:Fibroblasts / Q000382:microbiology; D006801:Humans; D008264:Macrophages / Q000382:microbiology*; D051379:Mice; D012285:Orientia tsutsugamushi / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
D002966:Clathrin