Department of Cell Biology, Yale School of Medicine, New Haven, CT 06520.
The Rockefeller University, New York, NY 10065.
Mol Biol Cell. 2021 Jul 15;32(15):1359-1373. doi: 10.1091/mbc.E20-09-0584. Epub 2021 May 19.
Integral membrane proteins of the Lap2-emerin-MAN1 (LEM) family have emerged as important components of the inner nuclear membrane (INM) required for the functional and physical integrity of the nuclear envelope. However, like many INM proteins, there is limited understanding of the biochemical interaction networks that enable LEM protein function. Here, we show that Heh2/Man1 can interact with major scaffold components of the nuclear pore complex (NPC), specifically the inner ring complex (IRC), in evolutionarily distant yeasts. Although an N-terminal domain is required for Heh2 targeting to the INM, we demonstrate that more stable interactions with the NPC are mediated by a C-terminal winged helix (WH) domain, thus decoupling INM targeting and NPC binding. Inhibiting Heh2's interactions with the NPC by deletion of the Heh2 WH domain leads to NPC clustering. Interestingly, Heh2's association with NPCs can also be disrupted by knocking out several outer ring nucleoporins. Thus, Heh2's interaction with NPCs depends on the structural integrity of both major NPC scaffold complexes. We propose a model in which Heh2 acts as a sensor of NPC assembly state, which may be important for NPC quality control mechanisms and the segregation of NPCs during cell division.
Lap2-emerin-MAN1（LEM）家族的完整膜蛋白已成为核膜功能和物理完整性所必需的核内层膜（INM）的重要组成部分。然而，与许多 INM 蛋白一样，对于使 LEM 蛋白发挥功能的生化相互作用网络的了解有限。在这里，我们表明 Heh2/Man1 可以与核孔复合物（NPC）的主要支架成分，特别是内环复合物（IRC），在进化上相距甚远的酵母中相互作用。尽管 N 端结构域是 Heh2 靶向 INM 所必需的，但我们证明与 NPC 更稳定的相互作用是由 C 端翼状螺旋（WH）结构域介导的，从而使 INM 靶向和 NPC 结合解耦。通过删除 Heh2 的 WH 结构域来抑制 Heh2 与 NPC 的相互作用会导致 NPC 聚集。有趣的是，敲除几个外环核孔蛋白也可以破坏 Heh2 与 NPC 的关联。因此，Heh2 与 NPC 的相互作用取决于两个主要 NPC 支架复合物的结构完整性。我们提出了一个模型，其中 Heh2 充当 NPC 组装状态的传感器，这对于 NPC 质量控制机制和 NPC 在细胞分裂过程中的分离可能很重要。
