G-CSFR Ubiquitination Critically Regulates Myeloid Cell Survival and Proliferation
G-CSFR Ubiquitination Critically Regulates Myeloid Cell Survival and Proliferation
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DOI：
10.1371/journal.pone.0003422
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发表时间：
2008-10-16
期刊：
影响因子：
3.7
通讯作者：
Avalos, Belinda R.
中科院分区：
文献类型：
--
作者：
Ai, Jing;Druhan, Lawrence J.;Avalos, Belinda R.
粒细胞集落刺激因子受体（G-CSFR）是粒细胞生成的关键调节因子。在患有严重先天性中性粒细胞减少症（SCN）转化为急性髓性白血病（AML）的患者中，G-CSFR的突变已被证明可诱导对G-CSF的超敏反应和增强的生长反应。最近的研究已经证明了泛素/蛋白酶体系统在G-CSFR启动负信号传导中的重要性。为了进一步研究泛素化在调节G-CSFR信号传导中的作用，我们产生了G-CSFR的突变形式（K762 R/G-CSFR），其废除了泛素与G-CSFR的位置762处的赖氨酸残基的连接，该位置762在从SCN/AML患者分离的Delta 716 G-CSFR形式中缺失。在响应于G-CSF时，与用WT G-CSFR转染的细胞相比，在表达突变体K762 R/G-CSFR的细胞中G-CSFR的单/多泛素化受损。用K762 R/G-CSFR稳定转染的细胞显示出更高的增殖率，对G-CSF的敏感性增加，并且在细胞因子耗尽后存活率提高，与先前发表的Delta 716 G-CSFR突变体的数据相似。在K762 R/G-CSFR转染细胞中，G-CSF诱导的信号分子Stat 5和Akt的活化也增加，并且在G-CSF撤除后，它们的活化仍然延长。这些结果表明，泛素化是调节G-CSFR介导的增殖和细胞存活所必需的。在赖氨酸762处破坏G-CSFR泛素化的突变诱导对G-CSF的异常受体信号传导和过度增殖反应，这可能有助于白血病转化。
The granulocyte colony-stimulating factor receptor (G-CSFR) is a critical regulator of granulopoiesis. Mutations in the G-CSFR in patients with severe congenital neutropenia (SCN) transforming to acute myelogenous leukemia (AML) have been shown to induce hypersensitivity and enhanced growth responses to G-CSF. Recent studies have demonstrated the importance of the ubiquitin/proteasome system in the initiation of negative signaling by the G-CSFR. To further investigate the role of ubiquitination in regulating G-CSFR signaling, we generated a mutant form of the G-CSFR (K762R/G-CSFR) which abrogates the attachment of ubiquitin to the lysine residue at position 762 of the G-CSFR that is deleted in the Delta 716 G-CSFR form isolated from patients with SCN/AML. In response to G-CSF, mono-/polyubiquitination of the G-CSFR was impaired in cells expressing the mutant K762R/G-CSFR compared to cells transfected with the WT G-CSFR. Cells stably transfected with the K762R/G-CSFR displayed a higher proliferation rate, increased sensitivity to G-CSF, and enhanced survival following cytokine depletion, similar to previously published data with the Delta 716 G-CSFR mutant. Activation of the signaling molecules Stat5 and Akt were also increased in K762R/G-CSFR transfected cells in response to G-CSF, and their activation remained prolonged after G-CSF withdrawal. These results indicate that ubiquitination is required for regulation of G-CSFR-mediated proliferation and cell survival. Mutations that disrupt G-CSFR ubiquitination at lysine 762 induce aberrant receptor signaling and hyperproliferative responses to G-CSF, which may contribute to leukemic transformation.