美国加州大学Young-wook Jun和Zev J. Gartner小组合作的最新研究表明，粘附连接（AJ）组织大小选择性蛋白水解热点对Notch信号至关重要。相关论文于2022年12月1日发表在《自然-细胞生物学》杂志上。

使用机械发生平台生成具有受控蛋白质定位，聚类和机械负载的人工AJ，研究人员发现AJ还调控了γ分泌酶的蛋白水解热点，并具有空间调节的底物选择性，这对于Notch和其他跨膜蛋白的加工至关重要。AJ外部的膜微域特异性调控Notch配体-受体接合（LRE微域）以启动受体激活。相反，AJ中的膜微域特异性调节膜内蛋白水解（RIP微域）。它们通过聚集γ分泌酶和引物受体来做到这一点，同时排除全长的Notch蛋白。

AJ通过脂质依赖性γ分泌酶的招募和分子量依赖性蛋白质分离诱导这些功能不同的微结构域。通过从RIP微域中排除全长Notch，AJ可防止不适当的酶-底物相互作用并抑制杂散Notch激活。配体诱导的胞外域脱落消除了大小依赖性偏析，释放的Notch易位到AJ中，通过γ分泌酶进行处理。该机制指导体内心室区-神经祖细胞的径向分化，并更广泛地调节其他大细胞表面受体（如淀粉样蛋白前体蛋白）的蛋白水解。

这些发现表明，AJ在创建大小选择性空间开关方面具有前所未知的作用，这些开关调节了与发育、稳态和疾病相关多种跨膜蛋白的γ分泌酶处理。

附：英文原文

Title: Adherens junctions organize size-selective proteolytic hotspots critical for Notch signalling

Author: Kwak, Minsuk, Southard, Kaden M., Kim, Woon Ryoung, Lin, Annie, Kim, Nam Hyeong, Gopalappa, Ramu, Lee, Hyun Jung, An, Minji, Choi, Seo Hyun, Jung, Yunmin, Noh, Kunwoo, Farlow, Justin, Georgakopoulos, Anastasios, Robakis, Nikolaos K., Kang, Min K., Kutys, Matthew L., Seo, Daeha, Kim, Hyongbum Henry, Kim, Yong Ho, Cheon, Jinwoo, Gartner, Zev J., Jun, Young-wook

Issue&Volume: 2022-12-01

Abstract: Adherens junctions (AJs) create spatially, chemically and mechanically discrete microdomains at cellular interfaces. Here, using a mechanogenetic platform that generates artificial AJs with controlled protein localization, clustering and mechanical loading, we find that AJs also organize proteolytic hotspots for γ-secretase with a spatially regulated substrate selectivity that is critical in the processing of Notch and other transmembrane proteins. Membrane microdomains outside of AJs exclusively organize Notch ligand–receptor engagement (LRE microdomains) to initiate receptor activation. Conversely, membrane microdomains within AJs exclusively serve to coordinate regulated intramembrane proteolysis (RIP microdomains). They do so by concentrating γ-secretase and primed receptors while excluding full-length Notch. AJs induce these functionally distinct microdomains by means of lipid-dependent γ-secretase recruitment and size-dependent protein segregation. By excluding full-length Notch from RIP microdomains, AJs prevent inappropriate enzyme–substrate interactions and suppress spurious Notch activation. Ligand-induced ectodomain shedding eliminates size-dependent segregation, releasing Notch to translocate into AJs for processing by γ-secretase. This mechanism directs radial differentiation of ventricular zone-neural progenitor cells in vivo and more broadly regulates the proteolysis of other large cell-surface receptors such as amyloid precursor protein. These findings suggest an unprecedented role of AJs in creating size-selective spatial switches that choreograph γ-secretase processing of multiple transmembrane proteins regulating development, homeostasis and disease.

DOI: 10.1038/s41556-022-01031-6

Source: https://www.nature.com/articles/s41556-022-01031-6