Molecular insights into the targeting of proteins to the inner nuclear membrane

我们的细胞含有数千种不同的蛋白质，它们组装在一个称为细胞质的亚区室中。从那里，它们被定位到各种蜂窝位置以执行其任务。其中一个目的地是细胞核，它包含我们的遗传信息，并由双层信封界定。对于到达核基质的蛋白质，已经确定了几个信号，并且核输入由通过穿过核膜的小孔操作的复杂机制介导。相比之下，蛋白质插入最内层核膜的分子细节仍然模糊不清，澄清它们对于更好地理解这些蛋白质的功能至关重要。 病毒是细胞内的寄生虫，其繁殖依赖于细胞机制。这使得它们成为研究我们如何运作的理想工具，因为它们比我们简单得多。其中，单纯疱疹病毒I型（HSV-1）是通常与唇疱疹相关的病毒，但它也会导致大量更严重的疾病，如脑炎和失明。一些HSV-1病毒蛋白靶向核膜。至于细胞蛋白质，目前尚不清楚它们如何到达该隔室，但它们可能依赖于现有的细胞装置。有趣的是，这些病毒蛋白质在感染过程中动态地重新定位，提高了病毒可以在空间和时间上调节这种细胞运输机制的有趣可能性。这使得HSV-1成为一个令人兴奋的模型，以更好地了解蛋白质靶向核膜。其中，病毒糖蛋白M（gM）具有潜在的核膜分选基序，是第一个检测到的几种病毒蛋白。随着感染的进行，这种病毒糖蛋白移出细胞核，表明其定位受到细胞和/或其他病毒成分的影响。我们最近的实验暗示了几个新的gM相互作用伙伴。因此，病毒gM蛋白构成了研究这种细胞靶向过程并确定病毒如何调节它的一个很好的候选者。我们研究计划的长期目标是了解蛋白质靶向核膜，探索这种分类机制的普遍性，并确定病毒是否以及如何调节它。我们未来5年的具体目标是：探索gM如何被带到内核靶向，B）阐明细胞核和细胞其余部分之间的核通道的作用，C）弄清楚gM最终如何从细胞核释放。为了实现这些目标，将采用大量的现代和互补技术，包括成像技术以及病毒学、细胞生物学和系统生物学工具。

Our cells contain thousands of different proteins, which are assembled inside a subcompartment called cytoplasm. From there, they are targeted to a variety of cellular locations to perform their tasks. One of these destinations is the nucleus, which contains our genetic information and is delimited by a double-layered envelope. For proteins reaching the nuclear matrix, several signals have been identified and nuclear import is mediated by a complex machinery operating through small holes traversing the nuclear envelopes. In contrast, the molecular details by which proteins are inserted within the innermost nuclear envelope are still nebulous and clarifying them is critical to better understand the function of these proteins. Viruses are intracellular parasites that depend on cellular machineries for their propagation. This makes them ideal tools to study how we function, since much simpler than us. Among them, the Herpes simplex virus type I (HSV-1) is the virus commonly associated with cold sores but it also causes a plethora of more severe diseases such as encephalitis and blindness. Some of HSV-1 viral proteins are targeted to nuclear membranes. As for cellular proteins, it is, however, not clear how they reach that compartment but they likely rely on an existing cellular apparatus. Interestingly, these viral proteins are dynamically re-localized during the infection, raising the intriguing possibility that the virus can spatially and temporally regulate this cellular transport machinery. This makes HSV-1 an exciting model to better understand targeting of proteins to the nuclear envelopes. Among them, the viral glycoprotein M (gM) possesses a potential nuclear membrane sorting motif and is the first of several viral proteins detected there. This viral glycoprotein moves out of the nucleus as the infection proceeds, indicating that its localization is influenced by cellular and/or other viral components. Our recent experiments hint at several novel gM interaction partners. The viral gM protein thus constitutes a great candidate to study this cellular targeting process and define how viruses modulate it. The long-term goals of our research program are to understand the targeting of proteins to the nuclear membranes, probe the universality of this sorting machinery and define if and how viruses regulate it. Our specific aims for the next 5 years are to A) Probe how gM is brought to the inner nuclear targeting, B) Clarify the role of nuclear channels between the nucleus and the rest of the cell and C) Figure out how gM is ultimately released from the nucleus. To reach these goals, a vast array of modern and complementary technologies will be employed, including imaging techniques as well as virology, cell biology and system biology tools.