A conformational switch in the SCF-D3/MAX2 ubiquitin ligase facilitates strigolactone signalling
A conformational switch in the SCF-D3/MAX2 ubiquitin ligase facilitates strigolactone signalling
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DOI：
10.1038/s41477-022-01145-7
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发表时间：
2022-04-28
期刊：
影响因子：
18
通讯作者：
Shabek, Nitzan
中科院分区：
文献类型：
--
作者：
Tal, Lior;Palayam, Malathy;Shabek, Nitzan
独脚金内酯（SLs）是一类调节植物生长发育过程的激素。SL感知和信号激活涉及F-box E3泛素连接酶D3/MAX2和DWARF14 (D14) α / β -水解酶以SL依赖的方式相互作用，并靶向D53/SMXL6/7/8转录抑制因子（SMXLs）进行蛋白酶体介导的降解。D3/MAX2已被证明存在于多种构象状态中，其中c端螺旋（CTH）经历封闭到开放的动力学并调节D14结合和SL感知。尽管在体外发现了D3- d14相互作用的多种模式，但调控D3/MAX2 CTH靶向D53/ smxl构象开关的残基及其对SL信号传导的后续影响尚不清楚。在这里，我们通过利用离体和植物中的构象开关突变体阐明ASK1-D3/MAX2在SL信号传导中的功能动力学。我们报道了ASK1-D3突变体脱位CTH的晶体结构，并证明通过CRISPR-Cas9基因组编辑或点突变突变体的表达破坏CTH的可塑性会导致SL信号的损伤。我们发现ASK1-D3/MAX2 CTH的构象开关直接调节泛素介导的蛋白质降解。参与D53/ smxl sl依赖性募集和泛素化的移位构象和参与的构象对于多泛素化D53/ smxl和随后的蛋白酶体降解的D14的释放是必需的。最后，我们发现了一种有机酸代谢物，可以直接触发D3/MAX2 CTH构象开关。我们的发现揭示了SKP1-CUL1-F-box泛素连接酶在植物信号传导中的新调控功能。本研究阐明了泛素连接酶SCF D3/MAX2作为独角麦内酯信号传导的关键元件的功能动力学。D3/MAX2构象状态之间的转换调节底物靶向，并可由初级代谢物引发。
Strigolactones (SLs) are a class of plant hormones that regulate numerous processes of growth and development. SL perception and signal activation involves interaction between F-box E3 ubiquitin ligase D3/MAX2 and DWARF14 (D14) alpha/beta-hydrolase in a SL-dependent manner and targeting of D53/SMXL6/7/8 transcriptional repressors (SMXLs) for proteasome-mediated degradation. D3/MAX2 has been shown to exist in multiple conformational states in which the C-terminal helix (CTH) undergoes a closed-to-open dynamics and regulates D14 binding and SL perception. Despite the multiple modes of D3-D14 interactions found in vitro, the residues that regulate the conformational switch of D3/MAX2 CTH in targeting D53/SMXLs and the subsequent effect on SL signalling remain unclear. Here we elucidate the functional dynamics of ASK1-D3/MAX2 in SL signalling by leveraging conformational switch mutants in vitro and in plants. We report the crystal structure of a dislodged CTH of the ASK1-D3 mutant and demonstrate that disruptions in CTH plasticity via either CRISPR-Cas9 genome editing or expression of point mutation mutants result in impairment of SL signalling. We show that the conformational switch in ASK1-D3/MAX2 CTH directly regulates ubiquitin-mediated protein degradation. A dislodged conformation involved in D53/SMXLs SL-dependent recruitment and ubiquitination and an engaged conformation are required for the release of polyubiquitinated D53/SMXLs and subsequently D14 for proteasomal degradation. Finally, we uncovered an organic acid metabolite that can directly trigger the D3/MAX2 CTH conformational switch. Our findings unravel a new regulatory function of a SKP1-CUL1-F-box ubiquitin ligase in plant signalling.This study elucidates the functional dynamics of the ubiquitin ligase SCF D3/MAX2 as a key element in strigolactone signalling. The switch between D3/MAX2 conformational states regulates substrate targeting and can be elicited by a primary metabolite.