Donahue Daniel A, Porrot Françoise, Couespel Norbert, Schwartz Olivier
Institut Pasteur, Department of Virology, Virus and Immunity Unit, Paris, France
CNRS URA 3015, Paris, France.
J Virol. 2017 Feb 28;91(6). doi: 10.1128/JVI.02303-16. Print 2017 Mar 15.
Linker of nucleoskeleton and cytoskeleton (LINC) complexes connect the nucleus to the cytoskeleton in eukaryotic cells. We previously reported that the overexpression of SUN2, an inner nuclear membrane protein and LINC complex component, inhibits HIV infection between the steps of reverse transcription and nuclear import in a capsid-specific manner. We also reported that SUN2 silencing does not modulate HIV infection in several cell lines. Silencing of SUN2 was recently reported to decrease HIV infection of CD4 T cells, an effect which was suggested to result from modulation of cyclophilin A (CypA)-dependent steps of HIV infection. We confirm here that HIV infection of primary CD4 T cells is compromised in the absence of endogenous SUN2, and we extend these findings to additional viral strains. However, we find that CypA is not required for the decreased infection observed in SUN2-silenced cells and, conversely, that endogenous SUN2 is not required for the well-documented positive modulation of HIV infection by CypA. In contrast, CD4 T cells lacking SUN2 exhibit a considerable defect in proliferative capacity and display reduced levels of activation markers and decreased viability. Additionally, SUN2-silenced CD4 T cells that become infected support reduced levels of viral protein expression. Our results demonstrate that SUN2 is required for the optimal activation and proliferation of primary CD4 T cells and suggest that the disruption of these processes explains the contribution of endogenous SUN2 to HIV infection in primary lymphocytes. Linker of nucleoskeleton and cytoskeleton (LINC) complexes connect the nucleus to the cytoskeleton. We previously reported that the overexpression of the LINC complex protein SUN2 inhibits HIV infection by targeting the viral capsid and blocking infection before the virus enters the nucleus. A recent report showed that the depletion of endogenous SUN2 in primary CD4 T cells results in decreased HIV infection and that this involves cyclophilin A (CypA), a host protein that interacts with the capsid of HIV to promote infection. We confirm that HIV infection is reduced in CD4 T cells lacking SUN2, but we find no role for CypA. Instead, SUN2 silencing results in CD4 T cells with decreased viability and much lower proliferation rates. Our results show that SUN2 is required for optimal CD4 T cell activation and proliferation and explain the reduced level of HIV infection in the absence of SUN2.
核骨架与细胞骨架连接体（LINC）复合物在真核细胞中将细胞核与细胞骨架相连。我们之前报道过，SUN2（一种内核膜蛋白和LINC复合物组分）的过表达在逆转录和核输入步骤之间以衣壳特异性方式抑制HIV感染。我们还报道过，在几种细胞系中，SUN2沉默不会调节HIV感染。最近有报道称，SUN2沉默会降低CD4 T细胞的HIV感染，这种效应被认为是由亲环素A（CypA）依赖性的HIV感染步骤的调节导致的。我们在此证实，在缺乏内源性SUN2的情况下，原代CD4 T细胞的HIV感染会受损，并且我们将这些发现扩展到了其他病毒株。然而，我们发现，在SUN2沉默的细胞中观察到的感染减少并不需要CypA，相反，CypA对HIV感染的充分记录的正向调节也不需要内源性SUN2。相比之下，缺乏SUN2的CD4 T细胞在增殖能力方面存在相当大的缺陷，并且其活化标志物水平降低，活力下降。此外，被感染的SUN2沉默的CD4 T细胞支持的病毒蛋白表达水平降低。我们的结果表明，SUN2是原代CD4 T细胞最佳活化和增殖所必需的，并表明这些过程的破坏解释了内源性SUN2对原代淋巴细胞中HIV感染的作用。核骨架与细胞骨架连接体（LINC）复合物将细胞核与细胞骨架相连。我们之前报道过，LINC复合物蛋白SUN2的过表达通过靶向病毒衣壳并在病毒进入细胞核之前阻断感染来抑制HIV感染。最近的一份报告显示，原代CD4 T细胞中内源性SUN2的缺失导致HIV感染减少，并且这涉及亲环素A（CypA），一种与HIV衣壳相互作用以促进感染的宿主蛋白。我们证实，缺乏SUN2的CD4 T细胞中的HIV感染减少，但我们发现CypA没有作用。相反，SUN2沉默导致CD4 T细胞活力降低且增殖率低得多。我们的结果表明，SUN2是CD4 T细胞最佳活化和增殖所必需的，并解释了在没有SUN2的情况下HIV感染水平降低的原因。
