Sucrose-induced Receptor Kinase 1 is Modulated by an Interacting Kinase with Short Extracellular Domain
Sucrose-induced Receptor Kinase 1 is Modulated by an Interacting Kinase with Short Extracellular Domain
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DOI：
10.1074/mcp.ra119.001336
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发表时间：
2019-05
期刊：
影响因子：
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通讯作者：
X. Wu;Liang-Cui Chu;Lin Xi;Heidi Pertl-Obermeyer;Zhi Li;K. Skłodowski;Clara Sánchez-Rodríguez;G. Obermeyer;W. Schulze
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文献类型：
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作者：
X. Wu;Liang-Cui Chu;Lin Xi;Heidi Pertl-Obermeyer;Zhi Li;K. Skłodowski;Clara Sánchez-Rodríguez;G. Obermeyer;W. Schulze
详细研究了SIRK 1和QSK 1的受体激酶复合物对水通道蛋白的激活作用。基于磷酸化蛋白质组学、pulldown研究和生理学实验，我们认为SIRK 1可能作为主要受体与辅助受体QSK 1形成复合物。SIRK 1可以自磷酸化，然后转磷酸化QSK 1。磷酸化的QSK 1增强并稳定了与水通道蛋白的相互作用，作为受体激酶复合物的底物。图形摘要强调了尚未表征的受体激酶QSK 1的功能作用。SIRK 1受体激酶与QSK 1异聚体的激活模型。QSK 1在底物募集和复合物稳定中的作用。蔗糖作为光合作用的产物，是光合作用叶片向生长中的非光合器官如根和种子转运的主要碳水化合物。这些生长中的组织，除了碳水化合物的供应，还需要通过水通道蛋白摄取水分，以增强生长过程中的细胞扩张。先前的工作揭示了蔗糖诱导的受体激酶SIRK 1通过响应于外部蔗糖刺激的磷酸化来控制水通道蛋白的活性。在这里，我们提出了AT 3G 02880（QSK 1），一种具有短外部结构域的受体激酶，在SIRK 1活性调节中的调节作用。我们的研究结果表明，SIRK 1自磷酸化后，蔗糖处理的Ser-744。自磷酸化的SIRK 1然后与QSK 1和QSK 2相互作用并转磷酸化。在与QSK 1相互作用后，SIRK 1在其调节C-末端磷酸化位点磷酸化水通道蛋白。因此，在根原生质体膨胀测定中，qsk 1 qsk 2突变体在等渗蔗糖刺激下显示出降低的水流入速率，证实了与受体激酶SIRK 1参与相同的信号通路。大规模的磷酸蛋白质组学比较单一突变sirk 1，qsk 1，和双突变sirk 1 qsk 1显示，水通道蛋白的调节磷酸化依赖于活化的受体激酶复合物的SIRK 1，以及QSK 1。QSK 1因此作为辅助受体稳定和增强SIRK 1活性并募集底物蛋白，如水通道蛋白。
The activation of aquaporins by a receptor kinase complex of SIRK1 and QSK1 was studied in detail. Based on phosphoproteomics, pulldown studies and physiological experiments we conclude that SIRK1 may function as a main receptor which forms a complex with coreceptor QSK1. SIRK1 can autophosphorylate and then trans-phosphorylate QSK1. Phosphorylated QSK1 enhanced and stabilized the interaction with aquaporins as substrates of the receptor kinase complex. Graphical Abstract Highlights Functional role of a yet uncharacterized receptor kinase QSK1. Activation model for SIRK1 receptor kinase in a heteromer with QSK1. Role of QSK1 in substrate recruitment and stabilization of the complex. Sucrose as a product of photosynthesis is the major carbohydrate translocated from photosynthetic leaves to growing nonphotosynthetic organs such as roots and seeds. These growing tissues, besides carbohydrate supply, require uptake of water through aquaporins to enhance cell expansion during growth. Previous work revealed Sucrose Induced Receptor Kinase, SIRK1, to control aquaporin activity via phosphorylation in response to external sucrose stimulation. Here, we present the regulatory role of AT3G02880 (QSK1), a receptor kinase with a short external domain, in modulation of SIRK1 activity. Our results suggest that SIRK1 autophosphorylates at Ser-744 after sucrose treatment. Autophosphorylated SIRK1 then interacts with and transphosphorylates QSK1 and QSK2. Upon interaction with QSK1, SIRK1 phosphorylates aquaporins at their regulatory C-terminal phosphorylation sites. Consequently, in root protoplast swelling assays, the qsk1qsk2 mutant showed reduced water influx rates under iso-osmotic sucrose stimulation, confirming an involvement in the same signaling pathway as the receptor kinase SIRK1. Large-scale phosphoproteomics comparing single mutant sirk1, qsk1, and double mutant sirk1 qsk1 revealed that aquaporins were regulated by phosphorylation depending on an activated receptor kinase complex of SIRK1, as well as QSK1. QSK1 thereby acts as a coreceptor stabilizing and enhancing SIRK1 activity and recruiting substrate proteins, such as aquaporins.