The GSK3-like kinase BIN2 phosphorylates and destabilizes BZR1, a positive regulator of the brassinosteroid signaling pathway in Arabidopsis
The GSK3-like kinase BIN2 phosphorylates and destabilizes BZR1, a positive regulator of the brassinosteroid signaling pathway in Arabidopsis
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DOI：
10.1073/pnas.152342599
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发表时间：
2002-07-23
影响因子：
11.1
通讯作者：
Wang, ZY
中科院分区：
文献类型：
--
作者：
He, JX;Gendron, JM;Wang, ZY
类甾醇（BRs）是一类对植物正常生长和发育至关重要的甾体激素。BR信号转导涉及细胞表面受体BRI 1、作为负调节剂的糖原合成酶激酶-3样激酶BIN 2以及作为正调节剂的核蛋白BZR 1和BZR 2/BES 1。这些组成部分之间的相互作用尚不清楚。在这里，我们报告说，BR诱导BZR 1蛋白的去磷酸化和积累。使用蛋白酶体抑制剂MG 132的实验表明，BZR 1的磷酸化增加了其通过蛋白酶体机制的降解。BIN 2在酵母双杂交试验中直接与BZR 1相互作用，在体外磷酸化BZR 1，并在体内负调节BZR 1蛋白的积累。这些结果有力地表明，BIN 2磷酸化BZR 1并靶向其降解，BR信号传导通过抑制BIN 2活性导致BZR 1去磷酸化和积累。
Brassinosteroids (BRs) are a class of steroid hormones essential for normal growth and development in plants. BR signaling involves the cell-surface receptor BRI1, the glycogen synthase kinase-3-like kinase BIN2 as a negative regulator, and nuclear proteins BZR1 and BZR2/BES1 as positive regulators. The interactions among these components remain unclear. Here we report that BRs induce dephosphorylation and accumulation of BZR1 protein. Experiments using a proteasome inhibitor, MG132, suggest that phosphorylation of BZR1 increases its degradation by the proteasome machinery. BIN2 directly interacts with BZR1 in yeast two-hybrid assays, phosphorylates BZR1 in vitro, and negatively regulates BZR1 protein accumulation in vivo. These results strongly suggest that BIN2 phosphorylates BZR1 and targets it for degradation and that BR signaling causes BZR1 dephosphorylation and accumulation by inhibiting BIN2 activity.