Warren James C, Cassimeris Lynne
Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
Cell Motil Cytoskeleton. 2007 Sep;64(9):675-89. doi: 10.1002/cm.20215.
Adenoviruses (Ads) utilize host cell microtubules to traverse the intracellular space and reach the nucleus in a highly efficient manner. Previous studies have shown that Ad infection promotes the formation of stable, posttranslationally modified microtubules by a RhoA-dependent mechanism. Ad infection also shifts key parameters of microtubule dynamic instability by a Rac1-dependent mechanism, resulting in microtubules with lower catastrophe frequencies, persistent growth phases, and a bias toward net growth compared to microtubules in uninfected cells. Until now it was unclear whether changes in RhoGTPase activity or microtubule dynamics had a direct impact on the efficiency of Ad microtubule-dependent nuclear localization. Here we have performed synchronous Ad infections and utilized confocal microscopy to analyze the individual contributions of RhoA activation, Rac1 activation, microtubule stability, dynamic behavior, and posttranslational modifications on Ad nuclear localization efficiency (NLE). We found that drug-induced suppression of microtubule dynamics impaired Ad NLE by disrupting the radial organization of the microtubule array. When the microtubule array was maintained, the suppression or enhancement of microtubule turnover did not significantly affect Ad NLE. Furthermore, RhoA activation or the formation of acetylated microtubules did not enhance Ad NLE. In contrast, active Rac1 was required for efficient Ad nuclear localization. Because Rac1 mediates persistent growth of microtubules to the lamellar regions of cells, we propose that Ad-induced activation of Rac1 enhances the ability of microtubules to "search and capture" incoming virus particles.
腺病毒利用宿主细胞微管高效穿越细胞内空间并抵达细胞核。先前的研究表明，腺病毒感染通过一种RhoA依赖性机制促进稳定的、翻译后修饰的微管形成。腺病毒感染还通过一种Rac1依赖性机制改变微管动态不稳定性的关键参数，导致与未感染细胞中的微管相比，微管的灾难性频率更低、持续生长阶段更长且偏向于净生长。到目前为止，尚不清楚RhoGTPase活性或微管动力学的变化是否对腺病毒依赖微管的核定位效率有直接影响。在这里，我们进行了同步腺病毒感染，并利用共聚焦显微镜分析RhoA激活、Rac1激活、微管稳定性、动态行为和翻译后修饰对腺病毒核定位效率（NLE）的各自贡献。我们发现，药物诱导的微管动力学抑制通过破坏微管阵列的径向组织损害了腺病毒NLE。当微管阵列保持时，微管周转的抑制或增强并未显著影响腺病毒NLE。此外，RhoA激活或乙酰化微管的形成并未提高腺病毒NLE。相反，有效的腺病毒核定位需要活性Rac1。因为Rac1介导微管向细胞层状区域的持续生长，我们提出腺病毒诱导的Rac1激活增强了微管“搜索和捕获”传入病毒颗粒的能力。
