Zhang Zhenzhen, Chen Wei, Shi Zhubing, Pan Fan, Wang Daping
Cancer Immunology Center, Institute of Biomedicine and Biotechnology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China.
Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen, China.
FEBS J. 2025 Feb;292(3):602-618. doi: 10.1111/febs.17364. Epub 2024 Dec 19.
Contactin-2 (CNTN2), an immunoglobulin cell adhesion molecule (IgCAM) expressed on the neural cell surface, regulates the formation of myelin sheaths, facilitates communication between neurons and axoglial cells, and coordinates the migration of neural cells. However, the assembly of full-length CNTN2 is still not fully elucidated. Here, we found that the full-length human CNTN2 forms a concentration-dependent homodimer. We further determined the cryo-EM structures of the full-length CNTN2, revealing a novel bowknot-shaped scaffold constituted of the Ig1-6 repeats from two protomers, with the flexible ribbon-like FNIII repeats extending outward in opposite directions. The Ig1-6 domains, rather than the previously proposed Ig1-4 domains, have an indispensable role in mediating CNTN2-dependent cell adhesion and clustering. Moreover, structure-guided mutagenesis analyses supported the idea that CNTN2 homodimerization observed in our structure is essential for cell adhesion. Our findings offer novel insights into the mechanism through which CNTN2 forms a homodimer to maintain cell-cell contacts in the nervous system.
Contactin-2（CNTN2）是一种在神经细胞表面表达的免疫球蛋白细胞粘附分子（IgCAM），它调节髓鞘的形成，促进神经元与轴突胶质细胞之间的通讯，并协调神经细胞的迁移。然而，全长CNTN2的组装过程仍未完全阐明。在此，我们发现全长人CNTN2形成浓度依赖性同源二聚体。我们进一步确定了全长CNTN2的冷冻电镜结构，揭示了一种由两个原体的Ig1-6重复序列构成的新型蝴蝶结状支架，其柔性带状FNIII重复序列向相反方向向外延伸。在介导CNTN2依赖性细胞粘附和聚集方面，起不可或缺作用的是Ig1-6结构域，而非先前提出的Ig1-4结构域。此外，基于结构的诱变分析支持了我们结构中观察到的CNTN2同源二聚化对细胞粘附至关重要这一观点。我们的研究结果为CNTN2形成同源二聚体以维持神经系统中细胞间接触的机制提供了新的见解。
