Site-Specific Ubiquitination Determines Lysosomal Sorting and Signal Attenuation of the Granulocyte Colony-Stimulating Factor Receptor
Site-Specific Ubiquitination Determines Lysosomal Sorting and Signal Attenuation of the Granulocyte Colony-Stimulating Factor Receptor
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DOI：
10.1111/j.1600-0854.2009.00928.x
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发表时间：
2009-08-01
期刊：
影响因子：
4.5
通讯作者：
Touw, Ivo P.
中科院分区：
文献类型：
--
作者：
Woelfler, Albert;Irandoust, Mahban;Touw, Ivo P.
细胞因子受体的泛素化控制细胞内受体的路由和信号持续时间，但潜在的分子决定因素尚不清楚。细胞因子信号蛋白SOCS3的抑制子驱动粒细胞集落刺激因子受体(G-CSFR)的溶酶体降解，这依赖于SOCS3介导的位于保守的膜旁基序中的特定赖氨酸的泛素化。在这里，我们表明，尽管其他赖氨酸泛素化，但在膜的近端区域定位赖氨酸对于这一过程是必不可少的。无论是基序的重新分配还是泛素与G-CSFR C末端的融合都不能驱动溶酶体路由。然而，在这个区域内，赖氨酸可以在不失去功能的情况下向C末端移动12个氨基酸，这证明了线性排序基序的存在，并证明了赖氨酸相对于SOCS3对接位置的定位是灵活的。G-CSFR泛素化在内吞作用后达到高峰，被甲基-β-环糊精和高渗蔗糖抑制，内化缺陷的G-CSFR突变株泛素化严重减少，表明泛素化主要发生在内吞体内。除了阐明SOCS3介导的泛素化的结构和时空方面，这些发现还暗示在严重的先天性中性粒细胞减少症中发现的G-CSFR突变体的异常信号功能，这是一种具有高白血病风险的造血疾病。
Ubiquitination of cytokine receptors controls intracellular receptor routing and signal duration, but the underlying molecular determinants are unclear. The suppressor of cytokine signaling protein SOCS3 drives lysosomal degradation of the granulocyte colony-stimulating factor receptor (G-CSFR), depending on SOCS3-mediated ubiquitination of a specific lysine located in a conserved juxtamembrane motif. Here, we show that, despite ubiquitination of other lysines, positioning of a lysine within the membrane-proximal region is indispensable for this process. Neither reallocation of the motif nor fusion of ubiquitin to the C-terminus of the G-CSFR could drive lysosomal routing. However, within this region, the lysine could be shifted 12 amino acids toward the C-terminus without losing its function, arguing against the existence of a linear sorting motif and demonstrating that positioning of the lysine relative to the SOCS3 docking site is flexible. G-CSFR ubiquitination peaked after endocytosis, was inhibited by methyl-beta-cyclodextrin as well as hyperosmotic sucrose and severely reduced in internalization-defective G-CSFR mutants, indicating that ubiquitination mainly occurs at endosomes. Apart from elucidating structural and spatio-temporal aspects of SOCS3-mediated ubiquitination, these findings have implications for the abnormal signaling function of G-CSFR mutants found in severe congenital neutropenia, a hematopoietic disorder with a high leukemia risk.