Arita Minetaro
Department of Virology II, National Institute of Infectious Diseases , 4-7-1 Gakuen, Musashimurayama-shi, Tokyo 208-0011, Japan.
ACS Infect Dis. 2016 Feb 12;2(2):140-8. doi: 10.1021/acsinfecdis.5b00122. Epub 2015 Dec 16.
Phosphatidylinositol-4 kinase III β (PI4KB) and oxysterol-binding protein (OSBP) family I have been identified as the major targets of anti-enterovirus drug candidates. Resistance mutations in poliovirus (PV) to these inhibitors have been identified in viral 3A protein, represented by a G5318A (3A-Ala70Thr) mutation, but the mechanism of viral resistance to host PI4KB/OSBP inhibitors remained unknown. In this study, we found that a G5318A mutation enhances the basal levels of phosphatidylinositol 4-phosphate (PI4P) and of the 3A protein and decreases the levels of the 3AB protein during PV replication. The 3A protein acted as a major effector responsible for the resistance to PI4KB inhibitor, but did not enhance the PI4KB activity in vitro in contrast to the 2C, 2BC, 3AB, and 3D proteins. The 3AB protein acted as the primary target of a G5318A mutation and also as an effector. We identified novel resistance mutations to a PI4KB inhibitor [C5151U (3A-T14M) and C5366U (3A-H86Y) mutations] and found that there is a positive correlation between the extent of the resistance phenotype and the levels of the 3A proteins. These results suggested that the 3A protein overproduced by enhanced processing of the 3AB protein with the resistance mutations overcomes the inhibitory effect of PI4KB inhibitor on PV replication independently of the hyperactivation of the PI4KB/OSBP pathway.
磷脂酰肌醇-4激酶IIIβ（PI4KB）和甾醇结合蛋白（OSBP）家族I已被确定为抗肠道病毒候选药物的主要靶点。脊髓灰质炎病毒（PV）对这些抑制剂的耐药性突变已在病毒3A蛋白中被鉴定出来，以G5318A（3A-Ala70Thr）突变为代表，但病毒对宿主PI4KB/OSBP抑制剂的耐药机制仍不清楚。在本研究中，我们发现G5318A突变在PV复制过程中提高了磷脂酰肌醇4-磷酸（PI4P）和3A蛋白的基础水平，并降低了3AB蛋白的水平。3A蛋白是对PI4KB抑制剂耐药的主要效应因子，但与2C、2BC、3AB和3D蛋白相比，它在体外并未增强PI4KB的活性。3AB蛋白是G5318A突变的主要靶点，也是一个效应因子。我们鉴定了对PI4KB抑制剂的新耐药突变[C5151U（3A-T14M）和C5366U（3A-H86Y）突变]，并发现耐药表型的程度与3A蛋白的水平之间存在正相关。这些结果表明，具有耐药性突变的3AB蛋白通过增强加工而过量产生的3A蛋白，独立于PI4KB/OSBP途径的过度激活，克服了PI4KB抑制剂对PV复制的抑制作用。
