Ishibashi Mariko, Morita Naoko, Nomura-Kawaguchi Chisato, Shimizu Yohko, Wakita Takaji, Esumi Mariko
Department of Pathology, Nihon University school of Medicine, 30-1 Ohyaguchikami-cho, Itabashi-ku, Tokyo, 173-8610, Japan.
Arch Virol. 2014 Nov;159(11):2949-55. doi: 10.1007/s00705-014-2150-z. Epub 2014 Jun 26.
C-type lectin domain family 4, member M (CLEC4M), a trans-membrane protein specifically expressed in liver sinusoidal endothelial cells, is considered a candidate receptor for hepatotropism of hepatitis C virus (HCV). CLEC4M was previously reported to capture artificial HCVpp (pseudoparticle) and transmit it to hepatocytes (transinfection) via CLEC4M-positive cells. It is still not known whether CLEC4M acts as a receptor for HCVcc (cell-culture-produced HCV) transinfection or whether CLEC4M is an entry receptor for HCVcc. Initially, we established stably CLEC4M-positive and HCV-replication-permissive cell lines by introducing a CLEC4M expression vector into Huh7-25 cells (Huh7-25-CLEC4M) by transfection. Huh7-25 is a mutant cell line that is resistant to JFH-1 HCVcc due to the lack of expression of CD81 but permissive for replication of JFH1 HCV RNA. When Huh7-25-CLEC4M cells were infected with HCVcc and cultured for 6 days, none were positive for infection. Next, to examine whether CLEC4M functions as a receptor for transinfection, Huh7-25-CLEC4M cells were inoculated with HCVcc and thereafter co-cultured with Huh7-it cells, which are susceptible to HCV infection. The amount of HCV RNA was increased in Huh7-it cells co-cultured with Huh7-25-CLEC4M cells, and the transinfection was inhibited in the presence of anti-CLEC4M antibody during inoculation. Thus, CLEC4M cannot substitute for CD81 as an entry receptor for JFH-1 HCVcc. It just mediates transinfection without internalization of HCVcc. CD81 is still crucial for HCV entry into hepatocytes, and CLEC4M in liver sinusoidal endothelial cells may be responsible for hepatotropism of HCV infection by trapping circulating HCV to transmit it to adjacent hepatocytes.
C型凝集素结构域家族4成员M（CLEC4M）是一种在肝窦内皮细胞中特异性表达的跨膜蛋白，被认为是丙型肝炎病毒（HCV）嗜肝性的候选受体。此前有报道称，CLEC4M可捕获人工HCVpp（假病毒颗粒），并通过CLEC4M阳性细胞将其传递给肝细胞（转染）。目前尚不清楚CLEC4M是否作为HCVcc（细胞培养产生的HCV）转染的受体，或者CLEC4M是否是HCVcc的进入受体。最初，我们通过转染将CLEC4M表达载体导入Huh7-25细胞（Huh7-25-CLEC4M），从而建立了稳定的CLEC4M阳性且允许HCV复制的细胞系。Huh7-25是一种突变细胞系，由于缺乏CD81的表达而对JFH-1 HCVcc具有抗性，但允许JFH1 HCV RNA复制。当Huh7-25-CLEC4M细胞感染HCVcc并培养6天时，没有一个细胞感染呈阳性。接下来，为了检测CLEC4M是否作为转染受体发挥作用，将Huh7-25-CLEC4M细胞接种HCVcc，然后与易受HCV感染的Huh7-it细胞共培养。与Huh7-25-CLEC4M细胞共培养的Huh7-it细胞中HCV RNA量增加，并且在接种期间存在抗CLEC4M抗体时转染受到抑制。因此，CLEC4M不能替代CD81作为JFH-1 HCVcc的进入受体。它只是介导转染而不使HCVcc内化。CD81对于HCV进入肝细胞仍然至关重要，肝窦内皮细胞中的CLEC4M可能通过捕获循环中的HCV并将其传递给相邻肝细胞而导致HCV感染的嗜肝性。
