Hahn Friedrich, Schmalen Adrian, Setz Christian, Friedrich Melanie, Schlößer Stefan, Kölle Julia, Spranger Robert, Rauch Pia, Fraedrich Kirsten, Reif Tatjana, Karius-Fischer Julia, Balasubramanyam Ashok, Henklein Petra, Fossen Torgils, Schubert Ulrich
Institute of Virology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
Translational Metabolism Unit, Diabetes Research Center, Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, Texas, United States of America.
PLoS One. 2017 Apr 7;12(4):e0174254. doi: 10.1371/journal.pone.0174254. eCollection 2017.
There is a significantly higher risk for type II diabetes in HIV-1 carriers, albeit the molecular mechanism for this HIV-related pathology remains enigmatic. The 52 amino acid HIV-1 p6 Gag protein is synthesized as the C-terminal part of the Gag polyprotein Pr55. In this context, p6 promotes virus release by its two late (L-) domains, and facilitates the incorporation of the viral accessory protein Vpr. However, the function of p6 in its mature form, after proteolytic release from Gag, has not been investigated yet. We found that the mature p6 represents the first known viral substrate of the ubiquitously expressed cytosolic metalloendopeptidase insulin-degrading enzyme (IDE). IDE is sufficient and required for degradation of p6, and p6 is approximately 100-fold more efficiently degraded by IDE than its eponymous substrate insulin. This observation appears to be specific for HIV-1, as p6 proteins from HIV-2 and simian immunodeficiency virus, as well as the 51 amino acid p9 from equine infectious anaemia virus were insensitive to IDE degradation. The amount of virus-associated p6, as well as the efficiency of release and maturation of progeny viruses does not depend on the presence of IDE in the host cells, as it was shown by CRISPR/Cas9 edited IDE KO cells. However, HIV-1 mutants harboring IDE-insensitive p6 variants exhibit reduced virus replication capacity, a phenomenon that seems to depend on the presence of an X4-tropic Env. Furthermore, competing for IDE by exogenous insulin or inhibiting IDE by the highly specific inhibitor 6bK, also reduced virus replication. This effect could be specifically attributed to IDE since replication of HIV-1 variants coding for an IDE-insensitive p6 were inert towards IDE-inhibition. Our cumulative data support a model in which removal of p6 during viral entry is important for virus replication, at least in the case of X4 tropic HIV-1.
HIV-1携带者患II型糖尿病的风险显著更高，尽管这种与HIV相关的病理的分子机制仍然不明。52个氨基酸的HIV-1 p6 Gag蛋白作为Gag多聚蛋白Pr55的C末端部分被合成。在这种情况下，p6通过其两个晚期（L-）结构域促进病毒释放，并促进病毒辅助蛋白Vpr的掺入。然而，p6从Gag蛋白水解释放后的成熟形式的功能尚未得到研究。我们发现成熟的p6是普遍表达的胞质金属内肽酶胰岛素降解酶（IDE）的首个已知病毒底物。IDE对于p6的降解是充分且必要的，并且p6被IDE降解的效率比其同名底物胰岛素高约100倍。这一观察结果似乎是HIV-1特有的，因为来自HIV-2和猴免疫缺陷病毒的p6蛋白，以及来自马传染性贫血病毒的51个氨基酸的p9蛋白对IDE降解不敏感。如CRISPR/Cas9编辑的IDE基因敲除细胞所示，病毒相关p6的量以及子代病毒释放和成熟的效率并不取决于宿主细胞中IDE的存在。然而，携带对IDE不敏感的p6变体的HIV-1突变体表现出病毒复制能力降低，这一现象似乎取决于X4嗜性Env的存在。此外，外源性胰岛素与IDE竞争或用高度特异性抑制剂6bK抑制IDE，也会降低病毒复制。这种效应可特异性归因于IDE，因为编码对IDE不敏感的p6的HIV-1变体的复制对IDE抑制不敏感。我们的累积数据支持一种模型，即在病毒进入过程中去除p6对病毒复制很重要，至少在X4嗜性HIV-1的情况下是这样。
