Mechanistic basis for the activation of plant membrane receptor kinases by SERK-family coreceptors.
Mechanistic basis for the activation of plant membrane receptor kinases by SERK-family coreceptors.
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DOI：
10.1073/pnas.1714972115
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发表时间：
2018-03-27
影响因子：
11.1
通讯作者：
Hothorn M
中科院分区：
文献类型：
--
作者：
Hohmann U;Santiago J;Nicolet J;Olsson V;Spiga FM;Hothorn LA;Butenko MA;Hothorn M
植物含有一种独特的膜受体家族，与细菌和动物中发现的不同。这些蛋白质能够感知非常不同的信号，如类固醇分子、多肽和细胞表面的蛋白质，使用螺旋形的配体结合域。配体结合允许受体与不同受体共享的较小的辅助受体激酶结合。本文分析了一种共受体蛋白如何参与植物生长和器官脱落的两种不同配体的感知以及它们的同源受体的激活。植物特有的富含亮氨酸重复胞外区的膜受体蛋白(LRR-RKS)可以识别小分子、多肽和蛋白质配体。许多LRR-RKs需要Serk家族的辅受体激动酶来进行高亲和力的配体结合和受体激活。一个辅助受体如何有助于不同配体的特异性结合和不同LRR-RKs的激活，目前还知之甚少。在这里，我们定量分析了SERK3在油菜素类固醇受体BRI1和多肽激素受体HAESA的配体结合和激活中的作用。我们表明，虽然分离的受体以截然不同的结合亲和力感知各自的配体，但SERK3胞外结构域以非常相似的结合动力学结合配体相关的受体。我们确定了SERK3 N末端封闭域中的残基，这使得选择性类固醇和多肽激素识别成为可能。相反，SERK3LRR核心中的残基形成了第二个结构性受体-辅受体界面。对BRI1和SERK3之间的蛋白质嵌合体的遗传分析表明，植物中的受体-辅受体异构化形成了具有信号功能的复合体。一个功能性的BRI1-HAESA嵌合体表明，受体的激活机制在不同的LRR-RKs之间是保守的，并且它们的信号特异性编码在受体的激动域中。我们的工作明确了受体、配体和辅助受体在调节植物生长发育的依赖于SERK的LRR-RK信号复合体的形成和激活中的相对作用。
Plants contain a unique family of membrane receptors, which are different from the ones found in bacteria and animals. These proteins are able to sense very different signals, such as steroid molecules, peptides, and proteins at the cell surface using a spiral-shaped ligand binding domain. Ligand binding allows the receptor to engage with a smaller coreceptor kinase, which is shared among different receptors. Here it is analyzed how one coreceptor protein can contribute to the sensing of two different ligands involved in plant growth and organ abscission and to activation of their cognate receptors. Plant-unique membrane receptor kinases with leucine-rich repeat ectodomains (LRR-RKs) can sense small molecule, peptide, and protein ligands. Many LRR-RKs require SERK-family coreceptor kinases for high-affinity ligand binding and receptor activation. How one coreceptor can contribute to the specific binding of distinct ligands and activation of different LRR-RKs is poorly understood. Here we quantitatively analyze the contribution of SERK3 to ligand binding and activation of the brassinosteroid receptor BRI1 and the peptide hormone receptor HAESA. We show that while the isolated receptors sense their respective ligands with drastically different binding affinities, the SERK3 ectodomain binds the ligand-associated receptors with very similar binding kinetics. We identify residues in the SERK3 N-terminal capping domain, which allow for selective steroid and peptide hormone recognition. In contrast, residues in the SERK3 LRR core form a second, constitutive receptor–coreceptor interface. Genetic analyses of protein chimera between BRI1 and SERK3 define that signaling-competent complexes are formed by receptor–coreceptor heteromerization in planta. A functional BRI1–HAESA chimera suggests that the receptor activation mechanism is conserved among different LRR-RKs, and that their signaling specificity is encoded in the kinase domain of the receptor. Our work pinpoints the relative contributions of receptor, ligand, and coreceptor to the formation and activation of SERK-dependent LRR-RK signaling complexes regulating plant growth and development.
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