美国加州南旧金山基因泰克公司Ishan Deshpande和Vishva M. Dixit共同合作，近期取得重要工作进展。他们研究提出，二聚体NINJ1的自身抑制可防止质膜破裂。相关研究成果2024年10月30日在线发表于《自然》杂志上。

据介绍，裂解性细胞死亡以质膜破裂（PMR）告终，这一过程释放出大量细胞内分子以增强炎症反应。PMR由效应膜蛋白ninjurin-1（NINJ1）介导，NINJ1通过其亲水表面聚合并破坏细胞膜。然而，NINJ1在稳态条件下如何受到抑制以确保细胞存活仍是一个未解之谜。

研究人员描述了NINJ1抑制的分子机制。利用冷冻电镜，研究人员解析了与新开发的纳米抗体Nb538结合的非活性状态小鼠NINJ1的结构。非活性NINJ1通过采用3螺旋结构（其中跨膜螺旋1，TM1，无弯曲）形成面对面的同源二聚体，这与4螺旋TM1弯曲的活性构象形成对比。

因此，来自原代巨噬细胞的内源性NINJ1在稳态条件下为二聚体。非活性二聚体将NINJ1的PMR诱导亲水面封闭，并阻挡邻近活化NINJ1分子弯曲TM1的结合位点。细胞中的突变研究表明，破坏非活性面对面二聚体的稳定性会导致NINJ1介导的细胞死亡，而稳定面对面二聚体则可抑制NINJ1活性。

此外，不稳定突变会促使自发的TM1弯曲形成，这是NINJ1活化的标志。

总之，这一研究表明，二聚体NINJ1通过反式自抑制来防止未触发的PMR和细胞死亡。

附：英文原文

Title: Autoinhibition of dimeric NINJ1 prevents plasma membrane rupture

Author: Pourmal, Sergei, Truong, Melissa E., Johnson, Matthew C., Yang, Ying, Zhou, Lijuan, Alegre, Kamela, Stowe, Irma B., Gupta, Shalini, Chen, Phoebe A., Zhang, Yingnan, Rohou, Alexis, Newton, Kim, Kayagaki, Nobuhiko, Dixit, Vishva M., Deshpande, Ishan

Issue&Volume: 2024-10-30

Abstract: Lytic cell death culminates in plasma membrane rupture (PMR), which releases large intracellular molecules to augment the inflammatory response. PMR is mediated by the effector membrane protein ninjurin-1 (NINJ1)1, which polymerises and ruptures the membrane via its hydrophilic face1–4. How NINJ1 is restrained under steady-state conditions to ensure cell survival remains a mystery. Here we describe the molecular underpinnings of NINJ1 inhibition. Using cryogenic electron microscopy, we determined the structure of inactive-state mouse NINJ1 bound to a newly-developed nanobody, Nb538. Inactive NINJ1 forms a face-to-face homodimer by adopting a 3-helix conformation with unkinked transmembrane helix 1 (TM1), in contrast to the 4-helix TM1-kinked active conformation2–4. Accordingly, endogenous NINJ1 from primary macrophages is a dimer under steady-state conditions. Inactive dimers sequester the PMR-inducing hydrophilic face of NINJ1 and occlude the binding site for kinked TM1 from neighbouring activated NINJ1 molecules. Mutagenesis studies in cells show that destabilisation of inactive face-to-face dimers leads to NINJ1-mediated cell death, whereas stabilisation of face-to-face dimers inhibits NINJ1 activity. Moreover, destabilising mutations prompt spontaneous TM1 kink formation, a hallmark of NINJ1 activation. Collectively, our data demonstrate that dimeric NINJ1 is autoinhibited in trans to prevent unprovoked PMR and cell death.

DOI: 10.1038/s41586-024-08273-4

Source: https://www.nature.com/articles/s41586-024-08273-4