Double inhibition and activation mechanisms of Ephexin family RhoGEFs
Double inhibition and activation mechanisms of Ephexin family RhoGEFs
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Ephexin家族RhoGEF的双重抑制和激活机制
DOI：
10.1073/pnas.2024465118
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发表时间：
2021-02-23
影响因子：
11.1
通讯作者：
Zhu，Jinwei
中科院分区：
文献类型：
--
作者：
Zhang，Meng;Lin，Lin;Zhu，Jinwei
意义Ephexin家族鸟嘌呤核苷酸交换因子（GEFs）在Eph信号的下游调节细胞骨架动力学，在多种细胞过程中发挥关键作用。为了实现Eph信号传导的精确调节，需要严格控制Ephexins的GEF活性。我们在这里提出了自抑制Ephexin 4的晶体结构，这表明N-和C-末端片段直接接触并抑制Ephexin 4的DH催化结构域。这种双重抑制机制可能通常被其他Ephexins和SGEF利用。保守酪氨酸在其N末端的磷酸化和PDZ蛋白与其C末端PDZ结合基序的缔合可以缓解自身抑制的Ephexin 4。这些结果揭示了微调Ephexin家族RhoGEFs的GEF活性的多功能自抑制机制。Ephexin家族鸟嘌呤核苷酸交换因子（GEF）将信号从Eph酪氨酸激酶受体转移到Rho GTP酶，Rho GTP酶在多种细胞过程以及癌症和脑疾病中起关键作用。在这里，我们阐明了抑制和激活Ephexin家族RhoGEFs的分子基础。部分和完全自抑制的Ephexin 4的晶体结构揭示，完全的自抑制需要N-和C-末端抑制模式，其可以独立地操作以阻止Ras同系物家族成员G（RhoG）进入。这种双重抑制机制通常由其他Ephexins和SGEF（RhoG的另一种RhoGEF）采用。结构、酶和细胞生物学分析表明，其N末端抑制结构域中保守酪氨酸残基的磷酸化以及PDZ蛋白与其C末端PDZ结合基序的结合可以分别缓解Ephexin 4中的两种自抑制模式。我们的研究为理解Ephexin 4 GEF活性的微调调节提供了一个机制框架，并为其病理功能障碍提供了可能的线索。
Significance Ephexin family guanine nucleotide exchange factors (GEFs) act downstream of Eph signaling to regulate cytoskeletal dynamics, playing critical roles in diverse cellular processes. To achieve precise regulation of Eph signaling, the GEF activities of Ephexins need to be tightly controlled. We here present the crystal structures of autoinhibited Ephexin4, which reveal that both N- and C-terminal fragments directly contact with and inhibit the DH catalytic domain of Ephexin4. This double inhibition mechanism may be commonly utilized by other Ephexins and SGEF. Phosphorylation of a conserved tyrosine at its N terminus and association of PDZ protein(s) to its C-terminal PDZ-binding motif may relieve the autoinhibited Ephexin4. These results reveal versatile autoinhibitory mechanisms that fine-tune the GEF activities of Ephexin family RhoGEFs. Ephexin family guanine nucleotide exchange factors (GEFs) transfer signals from Eph tyrosine kinase receptors to Rho GTPases, which play critical roles in diverse cellular processes, as well as cancers and brain disorders. Here, we elucidate the molecular basis underlying inhibition and activation of Ephexin family RhoGEFs. The crystal structures of partially and fully autoinhibited Ephexin4 reveal that the complete autoinhibition requires both N- and C-terminal inhibitory modes, which can operate independently to impede Ras homolog family member G (RhoG) access. This double inhibition mechanism is commonly employed by other Ephexins and SGEF, another RhoGEF for RhoG. Structural, enzymatic, and cell biological analyses show that phosphorylation of a conserved tyrosine residue in its N-terminal inhibitory domain and association of PDZ proteins with its C-terminal PDZ-binding motif may respectively relieve the two autoinhibitory modes in Ephexin4. Our study provides a mechanistic framework for understanding the fine-tuning regulation of Ephexin4 GEF activity and offers possible clues for its pathological dysfunction.