Halter Thierry, Imkampe Julia, Blaum Bärbel S, Stehle Thilo, Kemmerling Birgit
ZMBP; Plant Biochemistry; University Tübingen; Tübingen, Germany.
Interfaculty Institute of Biochemistry; University Tübingen; Tübingen, Germany.
Plant Signal Behav. 2014 Apr 29;9. doi: 10.4161/psb.28944.
BAK1 is a multifunctional leucine-rich repeat receptor kinase (LRR-RLK) that exerts its function by interacting with multiple ligand binding receptors and thereby influences diverse processes varying from brassinosteroid perception via PAMP and DAMP perception to cell death control. We recently identified a new BAK1 interacting protein, BIR2, that is also a LRR-RLK but, in contrast to BAK1, negatively regulates BAK1-dependent PAMP responses. While brassinosteroid responses are not affected by BIR2, cell death is negatively regulated as described for BAK1. BIR2 is released from BAK1 after ligand perception, increasing the pool of free BAK1 that is available to form complexes with activated ligand binding receptors. Individual ligands can only partially release BAK1 from BIR2. After exposition to a cocktail of ligands, almost the complete amount of BAK1 can be released indicating that BAK1 exists, together with BIR2, in subpools that can be individually addressed by specific ligands. These data support the idea that BAK1 exists in preformed complexes with its ligand binding receptor partners. Overexpression of BIR2 results in reduced complex formation of BAK1 with FLS2, showing that BIR2 negatively regulates BAK1 complex formation with ligand binding receptors.
BAK1是一种多功能富含亮氨酸重复序列的受体激酶（LRR-RLK），它通过与多种配体结合受体相互作用来发挥其功能，从而影响从油菜素类固醇感知、病原体相关分子模式（PAMP）和损伤相关分子模式（DAMP）感知到细胞死亡控制等多种不同过程。我们最近鉴定出一种新的与BAK1相互作用的蛋白BIR2，它也是一种LRR-RLK，但与BAK1相反，它对BAK1依赖性的PAMP反应起负调控作用。虽然油菜素类固醇反应不受BIR2影响，但细胞死亡如对BAK1的描述那样受到负调控。配体感知后，BIR2从BAK1上释放，增加了可用于与活化的配体结合受体形成复合物的游离BAK1的量。单个配体只能部分地从BIR2上释放BAK1。暴露于配体混合物后，几乎所有的BAK1都能被释放，这表明BAK1与BIR2一起存在于可被特定配体单独作用的亚池中。这些数据支持BAK1与其配体结合受体伙伴以预先形成的复合物形式存在的观点。BIR2的过表达导致BAK1与FLS2的复合物形成减少，表明BIR2对BAK1与配体结合受体形成复合物起负调控作用。
