Abstract：
The precise control of receptor levels is crucial for initiating cellular signaling transduction in response to specific ligands; however, such mechanisms regulating nodulation factor (NF) receptor (NFR)-mediated perception of NFs to establish symbiosis remain unclear. In this study, we unveil the pivotal role of the NFR-interacting RING-type E3 ligase 1 (NIRE1) in regulating NFR1/NFR5 homeostasis to optimize rhizobial infection and nodule development in Lotus japonicus. We demonstrated that NIRE1 has a dual function in this regulatory process. It associates with both NFR1 and NFR5, facilitating their degradation through K48-linked polyubiquitination before rhizobial inoculation. However, following rhizobial inoculation, NFR1 phosphorylates NIRE1 at a conserved residue, Tyr-109, inducing a functional switch in NIRE1, which enables NIRE1 to mediate K63-linked polyubiquitination, thereby stabilizing NFR1/NFR5 in infected root cells. The introduction of phospho-dead NIRE1Y109F leads to delayed nodule development, underscoring the significance of phosphorylation at Tyr-109 in orchestrating symbiotic processes. Conversely, expression of the phospho-mimic NIRE1Y109E results in the formation of spontaneous nodules in L. japonicus, further emphasizing the critical role of the phosphorylation-dependent functional switch in NIRE1. In summary, these findings uncover a fine-tuned symbiotic mechanism that a single E3 ligase could undergo a phosphorylation-dependent functional switch to dynamically and precisely regulate NF receptor protein levels.
摘要：
精确控制受体水平对于启动响应特定配体的细胞信号传导至关重要，然而,调控结瘤因子（NF）受体（NFR1/NFR5）感知NF建立共生的机制尚不清楚。这项研究揭示了NFR相互作用的RING型E3连接酶1（NIRE1）在调节NFR1/NFR5稳态以优化根瘤菌感染和根瘤发育中的关键作用。NIRE1在此调节过程中具有双重功能。NIRE1与NFR1/NFR5结合，在根瘤菌接种前通过K48连接的多泛素化促进其降解。根瘤菌接种后，NFR1在保守残基处磷酸化NIRE1，Tyr-109，在NIRE1中引起功能切换。该开关使NIRE1能够介导K63连接的聚泛素化，从而稳定受感染的根细胞中的NFR1/NFR5。磷死亡NIRE1Y109F的引入导致结节发育延迟,强调Tyr-109磷酸化在协调共生过程中的重要性。相反，磷酸化模拟物NIRE1Y109E的表达导致日本血吸虫自发结节的形成，进一步强调磷酸化依赖性功能开关在NIRE1中的关键作用。总之,这些发现提供了单一E3连接酶经历磷酸化依赖性功能开关的初步证据，动态和精确调节NF受体蛋白水平。
