Freiberg Fabian, Sauter Martina, Pinkert Sandra, Govindarajan Thirupugal, Kaldrack Joanna, Thakkar Meghna, Fechner Henry, Klingel Karin, Gotthardt Michael
Neuromuscular and Cardiovascular Cell Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany.
Department for Molecular Pathology, University Hospital Tübingen, Tübingen, Germany.
J Virol. 2014 Jul;88(13):7345-56. doi: 10.1128/JVI.00104-14. Epub 2014 Apr 16.
The coxsackievirus and adenovirus receptor (CAR) is a cell contact protein with an important role in virus uptake. Its extracellular immunoglobulin domains mediate the binding to coxsackievirus and adenovirus as well as homophilic and heterophilic interactions between cells. The cytoplasmic tail links CAR to the cytoskeleton and intracellular signaling cascades. In the heart, CAR is crucial for embryonic development, electrophysiology, and coxsackievirus B infection. Noncardiac functions are less well understood, in part due to the lack of suitable animal models. Here, we generated a transgenic mouse that rescued the otherwise embryonic-lethal CAR knockout (KO) phenotype by expressing chicken CAR exclusively in the heart. Using this rescue model, we addressed interspecies differences in coxsackievirus uptake and noncardiac functions of CAR. Survival of the noncardiac CAR KO (ncKO) mouse indicates an essential role for CAR in the developing heart but not in other tissues. In adult animals, cardiac activity was normal, suggesting that chicken CAR can replace the physiological functions of mouse CAR in the cardiomyocyte. However, chicken CAR did not mediate virus entry in vivo, so that hearts expressing chicken instead of mouse CAR were protected from infection and myocarditis. Comparison of sequence homology and modeling of the D1 domain indicate differences between mammalian and chicken CAR that relate to the sites important for virus binding but not those involved in homodimerization. Thus, CAR-directed anticoxsackievirus therapy with only minor adverse effects in noncardiac tissue could be further improved by selectively targeting the virus-host interaction while maintaining cardiac function.
Coxsackievirus B3 (CVB3) is one of the most common human pathogens causing myocarditis. Its receptor, the coxsackievirus and adenovirus receptor (CAR), not only mediates virus uptake but also relates to cytoskeletal organization and intracellular signaling. Animals without CAR die prenatally with major cardiac malformations. In the adult heart, CAR is important for virus entry and electrical conduction, but its nonmuscle functions are largely unknown. Here, we show that chicken CAR expression exclusively in the heart can rescue the otherwise embryonic-lethal CAR knockout phenotype but does not support CVB3 infection of adult cardiomyocytes. Our findings have implications for the evolution of virus-host versus physiological interactions involving CAR and could help to improve future coxsackievirus-directed therapies inhibiting virus replication while maintaining CAR's cellular functions.
柯萨奇病毒和腺病毒受体（CAR）是一种细胞接触蛋白，在病毒摄取中起重要作用。其细胞外免疫球蛋白结构域介导与柯萨奇病毒和腺病毒的结合以及细胞间的同源和异源相互作用。细胞质尾巴将CAR与细胞骨架和细胞内信号级联联系起来。在心脏中，CAR对胚胎发育、电生理学和柯萨奇病毒B感染至关重要。非心脏功能的了解较少，部分原因是缺乏合适的动物模型。在这里，我们生成了一种转基因小鼠，通过仅在心脏中表达鸡CAR来挽救原本会导致胚胎致死的CAR基因敲除（KO）表型。利用这个挽救模型，我们研究了柯萨奇病毒摄取的种间差异以及CAR的非心脏功能。非心脏CAR基因敲除（ncKO）小鼠的存活表明CAR在发育中的心脏中起重要作用，但在其他组织中并非如此。在成年动物中，心脏活动正常，这表明鸡CAR可以替代小鼠CAR在心肌细胞中的生理功能。然而，鸡CAR在体内不介导病毒进入，因此表达鸡而非小鼠CAR的心脏受到保护，免受感染和心肌炎。序列同源性比较和D1结构域的建模表明，哺乳动物和鸡的CAR之间存在差异，这些差异与病毒结合的重要位点有关，但与同源二聚化所涉及的位点无关。因此，通过在维持心脏功能的同时选择性地靶向病毒-宿主相互作用，可以进一步改进对非心脏组织只有轻微不良反应的CAR导向抗柯萨奇病毒疗法。
柯萨奇病毒B3（CVB3）是引起心肌炎的最常见人类病原体之一。其受体柯萨奇病毒和腺病毒受体（CAR）不仅介导病毒摄取，还与细胞骨架组织和细胞内信号传导有关。没有CAR的动物在产前会因严重心脏畸形而死亡。在成年心脏中，CAR对病毒进入和电传导很重要，但其非肌肉功能在很大程度上尚不清楚。在这里，我们表明仅在心脏中表达鸡CAR可以挽救原本会导致胚胎致死的CAR基因敲除表型，但不支持成年心肌细胞的CVB3感染。我们的发现对涉及CAR的病毒-宿主与生理相互作用的进化有影响，并有助于改进未来抑制病毒复制同时维持CAR细胞功能的柯萨奇病毒导向疗法。
