Moorhead A R, Rzomp K A, Scidmore M A
Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Infect Immun. 2007 Feb;75(2):781-91. doi: 10.1128/IAI.01447-06. Epub 2006 Nov 13.
Chlamydia species are obligate intracellular bacteria that replicate within a membrane-bound vacuole, the inclusion, which is trafficked to the peri-Golgi region by processes that are dependent on early chlamydial gene expression. Although neither the host nor the chlamydial proteins that regulate the intracellular trafficking have been clearly defined, several enhanced green fluorescent protein (EGFP)-tagged Rab GTPases, including Rab6, are recruited to Chlamydia trachomatis inclusions. To further characterize the association of Rab6 with C. trachomatis inclusions, we examined the intracellular localization of guanine nucleotide-binding mutants of Rab6 and demonstrated that only active GTP-bound and not inactive GDP-bound EGFP-Rab6 mutants were recruited to the inclusion, suggesting that EGFP-Rab6 interacts with the inclusion via a host Rab6 effector or a chlamydial protein that mimics a Rab6 effector. Using EGFP-tagged fusion proteins, we also demonstrated that the Rab6 effector Bicaudal D1 (BICD1) localized to C. trachomatis inclusions in a biovar-specific manner. In addition, we demonstrated that EGFP-Rab6 and its effector EGFP-BICD1 are recruited to the inclusion in a microtubule- and Golgi apparatus-independent but chlamydial gene expression-dependent mechanism. Finally, in contrast to the Rab6-dependent Golgi apparatus localization of endogenous BICD1, EGFP-BICD1 was recruited to the inclusion by a Rab6-independent mechanism. Collectively, these data demonstrate that neither Rab6 nor BICD1 is trafficked to the inclusion via a Golgi apparatus-localized intermediate, suggesting that each protein is trafficked to the C. trachomatis serovar L2 inclusion by a unique, but as-yet-undefined, mechanism.
衣原体属是专性细胞内细菌，在膜结合的液泡（包涵体）内复制，该包涵体通过依赖衣原体早期基因表达的过程被转运至高尔基体周围区域。尽管调控细胞内运输的宿主蛋白和衣原体蛋白均未明确界定，但几种增强型绿色荧光蛋白（EGFP）标记的Rab GTP酶，包括Rab6，会被募集到沙眼衣原体包涵体中。为了进一步表征Rab6与沙眼衣原体包涵体的关联，我们检测了Rab6鸟嘌呤核苷酸结合突变体的细胞内定位，并证明只有活性GTP结合型而非无活性GDP结合型的EGFP-Rab6突变体被募集到包涵体，这表明EGFP-Rab6通过宿主Rab6效应器或模拟Rab6效应器的衣原体蛋白与包涵体相互作用。使用EGFP标记的融合蛋白，我们还证明了Rab6效应器双尾D1（BICD1）以生物变种特异性方式定位于沙眼衣原体包涵体。此外，我们证明EGFP-Rab6及其效应器EGFP-BICD1通过一种不依赖微管和高尔基体但依赖衣原体基因表达的机制被募集到包涵体。最后，与内源性BICD1依赖Rab6的高尔基体定位相反，EGFP-BICD1通过一种不依赖Rab6的机制被募集到包涵体。总体而言，这些数据表明Rab6和BICD1都不是通过定位于高尔基体的中间体被转运至包涵体，这表明每种蛋白都是通过一种独特但尚未明确的机制被转运至沙眼衣原体血清型L2包涵体。
