Identification of a host protein that is necessary for the initial stage of HPV infection

人乳头瘤病毒(HPV)是人乳头瘤病毒科非囊膜DNA肿瘤病毒家族成员。与包膜病毒不同，HPV被认为利用自己的策略进入细胞并逃逸到细胞质中。然而，对初始感染阶段所需的细胞机制知之甚少。在这里，我们报道了运输蛋白颗粒复合体8亚单位(TRAPPC8)，一种与HPV微小衣壳蛋白L2相互作用的宿主蛋白，在HPV进入过程中起着至关重要的作用。TRAPPC8基因敲除的上皮细胞对假病毒(PSV)转导和真病毒感染的敏感性降低。TRAPPC8存在于HeLa细胞的胞浆和微粒体中。接种PSV后，C-末端暴露在细胞表面，并与PSV共定位。PSV和L2缺陷的PSV进入TRAPPC8基因敲除细胞的能力受到严重损害，这表明TRAPPC8在HPV以L2相互作用不依赖的方式进入细胞中起重要作用。另一方面，表达能与TRAPPC8相互作用的GFP融合的L2S诱导了高尔基体堆叠结构在HeLa细胞中的分散，这是TRAPPC8基因敲除观察到的一种表型。这些结果表明，在病毒的细胞内运输过程中，L2与TRAPPC8的结合抑制了其功能，导致高尔基失稳，这可能有助于HPV基因组在进入细胞后从反高尔基网络逃逸到细胞质或细胞核。

The human papillomavirus (HPV) is a member of the papillomaviridae family of non-enveloped DNA tumor viruses. Differing from enveloped viruses, HPVs are thought to gain cell entry and escape into the cytoplasm using their own strategy. However, the cellular machinery required for the initial infection stage is poorly understood. Here we report that transport protein particle complex subunit 8 (TRAPPC8), a host protein that interacts with HPV minor capsid protein L2, plays a crucial role in the HPV entry process. TRAPPC8-knockdown epithelial cells showed reduced susceptibility to pseudovirus (PsV) transduction and authentic virus infection. TRAPPC8 was present in cytosolic and microsomal fractions of HeLa cells. The C-terminal region was exposed on the cell surface and co-localized with PsV after inoculation with PsV. The entry of PsV and L2-deficient PsV into TRAPPC8-knockdown cells was severely impaired, suggesting that TRAPPC8 plays an important role in HPV entry in a L2 interaction-independent manner. On the other hand, expression of GFP-fused L2s that can interact with TRAPPC8 induced dispersal of Golgi stack structure in HeLa cells, which is a phenotype observed by TRAPPC8 knockdown. These results imply a possibility that during viral intracellular trafficking L2 binding to TRAPPC8 inhibits its function and results in Golgi de-stabilization, which may help an escape of the HPV genome from the trans-Golgi network into the cytoplasm or nucleus after attaining cell entry.