A Sphingomyelin Hydrolase Regulates the Late Stages of HIV Assembly and Budding

摘要 HIV组装发生在质膜上的专门的膜微区（通常称为微区）内。 作为脂质大鼠），其由于包括PIP 2的饱和脂质的富集而表现出降低的横向移动性， 神经酰胺、鞘磷脂和甾醇。HIV-1 Gag前体蛋白靶向这些细胞的内小叶， 质膜微区和调节病毒体组装和出芽所需的基本事件。 然而，Gag调节这些微区形成的机制以及这些微区的作用还有待进一步研究。 病毒组装中的微结构域目前是未知的。在这里，我们提供了第一个证据，Gag共定位 用鞘磷脂水解酶nSM酶2（其催化由鞘磷脂形成神经酰胺）， nSMase 2是HIV复制的关键调节因子。在初步实验中，我们发现， 酶是成功完成HIV装配和成熟的晚期阶段所必需的。 药理学抑制或nSM酶2的基因缺失阻止了Gag的加工，并导致 产生不规则形状的未成熟的非感染性病毒体。在人源化HIV感染的小鼠中， 在大多数受试动物中，nSMase 2使病毒载量线性降低至检测限以下。 更重要的是，通过治疗达到低于可检测限度的病毒载量的动物， 停药后反弹。这些研究的结果将增加我们的基本 通过首次描述nSMase 2和神经酰胺在病毒复制周期中的作用， 艾滋病毒复制。

ABSTRACT HIV assembly occurs at the plasma membrane within specialized membrane microdomains (commonly known as lipid rats) that exhibit reduced lateral mobility owing to an enrichment of saturated lipids including PIP2, ceramide, sphingomyelin, and sterols. The HIV-1 Gag precursor protein targets to the inner leaflet of these plasma membrane microdomains and regulates essential events required for virion assembly and budding. However, the mechanisms by which Gag regulates the formation of these microdomains and the role for these microdomains in viral assembly is currently unknown. Here we provide the first evidence that Gag co-localizes with the sphingomyelin hydrolase nSMase2 (which catalyzes the formation of ceramide from sphingomyelin), and that nSMase2 is a critical regulator of HIV replication. In preliminary experiments we discovered that this enzyme is required for the successful completion of the late stages of HIV assembly and maturation. Pharmacological inhibition or genetic deletion of nSMase2 prevented the processing of Gag and resulted in the production of irregularly shaped immature non-infectious virions. In humanized HIV infected mice, inhibition of nSMase2 produced a linear decrease of viral loads to below detectable limits in the majority of animals tested. More importantly, animals who achieved viral loads below detectable limits with treatment, did not exhibit viral rebound when drug administration was discontinued. The findings from these studies will increase our basic understanding of the viral replication cycle by describing for the first time a role for nSMase2 and ceramide in HIV replication.