Virus Host Interactions that Regulate Translation in Cells Infected with HSV-1

当单纯疱疹病毒（HSV）在人类外周神经元中建立永久性潜伏感染时，病毒繁殖受到抑制，一个导致感染性病毒生产的生长程序在生理应激下周期性启动。这种生产性生长程序要求HSV控制宿主蛋白质合成机制，以强制翻译病毒编码的mrna。宿主翻译抑制因子4E-BP1的失活是这一过程中的关键一步，其活性由多亚单位细胞激酶mTORC1控制。我们已经确定翻译抑制因子4E-BP1的失活需要病毒Us3丝氨酸苏氨酸激酶，其功能是激活mTORC1。值得注意的是，mTORC1是基本细胞合成代谢和分解代谢过程的关键调节因子，并准备维持细胞内的生理稳态。此外，各种各样的生理应激，其中许多抑制mTORC1信号传导并破坏代谢稳态，在潜在感染的神经元中触发生产性复制。我们的总体目标是了解Us3病毒丝氨酸苏氨酸激酶如何通过宿主mTORC1多亚基复合物（一种蛋白质合成的关键调节剂）破坏HSV1有效感染细胞中的信号传导。基于我们的初步结果，我们假设抑制mTORC1信号，以响应不断变化的环境条件或作为一种内在的宿主防御，可以限制病毒复制。随后mTORC1在Us3作用下的激活是刺激合成代谢功能（蛋白质合成）所必需的，从而使病毒复制多产，从而抵消旨在限制病毒生长的基本先天（分解代谢）宿主防御。在这里，这一假设在三个特定目标中得到验证：1)确定HSV1感染如何改变和操纵宿主多亚基mTORC1酶复合物的信号传导；ii)确定us3介导的mTORC1信号如何控制高产感染细胞中的病毒和细胞mRNA翻译；iii)定义调节mTORC1信号传导的生理应激如何控制HSV1的复制，以及Us3在缓解应激下的生产性生长方面的影响。确定宿主翻译控制途径如何调节生产性HSV1生长以及病毒功能如何在生理应激下保持其活性将改变我们对病毒-宿主相互作用的理解，并导致干扰病毒复制的新治疗策略。

While herpes simplex virus (HSV) establishes permanent latent infections in human peripheral neurons where virus reproduction is suppressed, a growth program resulting in infectious virus production periodically initiates in response to physiological stress. This productive growth program requires that HSV seize control of the host protein synthesis machinery to enforce translation of virus-encoded mRNAs. Inactivation of a host translational repressor, 4E-BP1, whose activity is controlled by the multi-subunit cellular kinase mTORC1 represents a key step in this process. We have established that inactivation of the translation repressor 4E-BP1 requires the viral Us3 Ser Thr kinase, which functions to activate mTORC1. Significantly, mTORC1 is a critical regulator of fundamental cellular anabolic and catabolic processes and is poised to maintain physiological homeostasis within cells. Moreover, a diverse assortment of physiological stresses, many of which inhibit mTORC1 signaling and disrupt metabolic homeostasis, trigger productive replication in latently-infected neurons. Our overall objective is to understand how the Us3 viral Ser Thr kinase can subvert signaling via the host mTORC1 multi-subunit complex, a key regulator of protein synthesis, in cells productively infected with HSV1. Based on our preliminary results, we hypothesize that suppressing mTORC1 signaling, in response to changing environmental conditions or as an intrinsic host defense, can limit virus replication. Subsequent mTORC1 activation in response to Us3 action is required to stimulate anabolic functions (protein synthesis) that enable productive viral replication, thus counteracting fundamental innate (catabolic) host defenses designed to limit viral growth. Here this hypothesis is tested in three specific aims that i) determine how HSV1 infection modifies and manipulates signaling by the host multi-subunit mTORC1 enzyme complex; ii) determine how Us3-mediated mTORC1 signaling controls viral and cellular mRNA translation in productively-infected cells; and iii) define how physiological stresses that regulate mTORC1 signaling control HSV1 replication and the impact of Us3 in mitigating productive growth under stress. Identifying how host translational control pathways regulate productive HSV1 growth and how viral functions preserve their activity under physiological stress will change our understanding of virus-host interactions and lead to new therapeutic strategies that interfere with viral replication.