Conformational landscape of soluble α-klotho revealed by cryogenic electron microscopy.
Conformational landscape of soluble α-klotho revealed by cryogenic electron microscopy.
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低温电子显微镜揭示可溶性α-klotho 的构象景观。
DOI：
10.1101/2024.03.02.583144
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发表时间：
2024
期刊：
影响因子：
--
通讯作者：
Huang,Chou-Long
中科院分区：
文献类型：
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作者：
Schnicker,NicholasJ;Xu,Zhen;Amir,Mohammad;Gakhar,Lokesh;Huang,Chou-Long
α-Klotho（KLA）是一种1型膜蛋白，可与成纤维细胞生长因子受体（FGFR）结合形成FGF 23的共受体。未结合的KLA的胞外域作为可溶性KLA（sKLA）脱落以发挥FGFR/FGF 23非依赖性多效性功能。先前确定的与FGF 23和FGFR 1c复合的sKLA胞外区的X射线晶体结构表明，sKLA仅作为FGF 23的按需辅助受体发挥作用。为了理解sKLA的FGFR/FGF 23独立的多效性功能，我们研究了apo-sKLA的生物物理性质和结构。单粒子低温电子显微镜（cryo-EM）揭示了一个3.3 μ m分辨率的apo-sKLA结构，它与三元复合物中的对应物重叠得很好，具有几个不同的特征。与三元复合物相比，apo-sKLA的KL 2结构域更灵活。三维可变性分析显示apo-sKLA采用具有不同KL 1-KL 2域间弯曲和旋转角的构象。质量光度法显示，sKLA可以与FGFR和/或FGF 23以及sKLA二聚体在溶液中形成稳定的结构。Cryo-EM支持sKLA的二聚体结构。最近的研究表明，FGF 23含有两个KLA结合位点。我们的计算研究表明，每个网站结合单独的KLA的二聚体。sKLA潜在的多种形式和形状支持其作为具有多效性功能的FGFR非依赖性激素的作用。FGF 23同时接合两个KLA的能力提高了膜klotho对FGF 23介导的信号传导的潜在新作用机制。
α-Klotho (KLA) is a type-1 membranous protein that can associate with fibroblast growth factor receptor (FGFR) to form co-receptor for FGF23. The ectodomain of unassociated KLA is shed as soluble KLA (sKLA) to exert FGFR/FGF23-independent pleiotropic functions. The previously determined X-ray crystal structure of the extracellular region of sKLA in complex with FGF23 and FGFR1c suggests that sKLA functions solely as an on-demand coreceptor for FGF23. To understand the FGFR/FGF23-independent pleiotropic functions of sKLA, we investigated biophysical properties and structure of apo-sKLA. Single particle cryogenic electron microscopy (cryo-EM) revealed a 3.3 Å resolution structure of apo-sKLA that overlays well with its counterpart in the ternary complex with several distinct features. Compared to the ternary complex, the KL2 domain of apo-sKLA is more flexible. Three-dimensional variability analysis revealed that apo-sKLA adopts conformations with different KL1-KL2 interdomain bending and rotational angles. Mass photometry revealed that sKLA can form a stable structure with FGFR and/or FGF23 as well as sKLA dimer in solution. Cryo-EM supported the dimeric structure of sKLA. Recent studies revealed that FGF23 contains two KLA-binding sites. Our computational studies revealed that each site binds separate KLA in the dimer. The potential multiple forms and shapes of sKLA support its role as FGFR-independent hormone with pleiotropic functions. The ability of FGF23 to engage two KLA’s simultaneously raises a potential new mechanism of action for FGF23-mediated signaling by the membranous klotho.