The obligate intracellular pathogen Chlamydia trachomatis has unique metabolic requirements as it proceeds through its biphasic developmental cycle from within the inclusion within the host cell. In our previous study, we identified a host protein, PICALM, which localizes to the chlamydial inclusion. PICALM functions in many host pathways including the recycling of receptors, specific SNARE proteins, and molecules like transferrin, and maintaining cholesterol homeostasis. Hence, we hypothesized that PICALM functions to maintain the cholesterol content and to moderate trafficking from the endosomal recycling pathway to the inclusion, which controls chlamydial access to this pathway. In uninfected cells, siRNA knockdown of PICALM resulted in increased cholesterol within the Golgi and transferrin receptor (TfR) positive vesicles (recycling endosomes). PICALM knockdown in cells infected with C. trachomatis resulted in increased levels of Golgi-derived lipid and protein, TfR, transferrin, and Rab11-FIP1 localized to inclusions and a decrease of Golgi fragmentation at and Rab11 trafficking to the inclusion. Interestingly, chlamydial infection alone also increases cholesterol in TfR and Rab11-associated vesicles, and PICALM knockdown reverses this effect. Our data suggest that PICALM functions to balance or limit chlamydial access to multiple subcellular trafficking pathways to maintain the health of the host cell during chlamydial infection.

中文翻译：

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真核细胞网格蛋白衔接蛋白和胆固醇稳态介质 PICALM 影响衣原体包涵体的运输。

专性细胞内病原体沙眼衣原体具有独特的代谢要求，因为它从宿主细胞内的包涵体进入其双相发育周期。在我们之前的研究中，我们发现了一种宿主蛋白​​ PICALM，它定位于衣原体包涵体。PICALM 在许多宿主通路中发挥作用，包括受体、特定 SNARE 蛋白和转铁蛋白等分子的循环，以及维持胆固醇稳态。因此，我们假设 PICALM 的功能是维持胆固醇含量并调节从内体循环途径到包涵体的运输，从而控制衣原体进入该途径。在未感染的细胞中，PICALM 的 siRNA 敲低导致高尔基体和转铁蛋白受体 (TfR) 阳性囊泡（再循环内体）内的胆固醇增加。感染沙眼衣原体的细胞中的 PICALM 敲低导致高尔基体衍生的脂质和蛋白质、TfR、转铁蛋白和定位于包涵体的 Rab11-FIP1 水平升高，并减少高尔基体碎片和 Rab11 运输到包涵体。有趣的是，单独的衣原体感染也会增加 TfR 和 Rab11 相关小泡中的胆固醇，而 PICALM 敲除可逆转这种作用。我们的数据表明，PICALM 的功能是平衡或限制衣原体进入多个亚细胞运输途径，以在衣原体感染期间维持宿主细胞的健康。有趣的是，单独的衣原体感染也会增加 TfR 和 Rab11 相关小泡中的胆固醇，而 PICALM 敲除可逆转这种作用。我们的数据表明，PICALM 的功能是平衡或限制衣原体进入多个亚细胞运输途径，以在衣原体感染期间维持宿主细胞的健康。有趣的是，单独的衣原体感染也会增加 TfR 和 Rab11 相关小泡中的胆固醇，而 PICALM 敲除可逆转这种作用。我们的数据表明，PICALM 的功能是平衡或限制衣原体进入多个亚细胞运输途径，以在衣原体感染期间维持宿主细胞的健康。