The localization of FGFR3 mutations causing thanatophoric dysplasia type I differentially affects phosphorylation, processing and ubiquitylation of the receptor
The localization of FGFR3 mutations causing thanatophoric dysplasia type I differentially affects phosphorylation, processing and ubiquitylation of the receptor
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DOI：
10.1111/j.1742-4658.2007.05835.x
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发表时间：
2007-07-01
期刊：
影响因子：
5.4
通讯作者：
Baron, Roland
中科院分区：
文献类型：
--
作者：
Bonaventure, Jacky;Gibbs, Linda;Baron, Roland
复发性错义成纤维细胞生长因子受体3（FGFR 3）突变已被归因于不同严重程度的骨骼发育不良，包括致死性新生儿致死性发育不良I型（TDI）和II型（TDII）。为了阐明激活突变导致TDI对受体运输和内吞作用的作用，产生并瞬时表达了位于受体不同结构域的一系列四种突变体。经鉴定，pupillary伸长的X807 R受体有三种亚型。完全糖基化的成熟同种型是组成性的，但轻度磷酸化。类似地，影响细胞外结构域的突变（R248 C和Y373 C）诱导中度组成性受体磷酸化。相比之下，K650 M突变影响酪氨酸激酶2（TK 2）结构域产生的非糖基化和甘露糖丰富的异构体，通过高尔基体网络受损的受体贩运严重磷酸化。这导致成熟同种型在细胞表面的表达缺陷。酪氨酸激酶抑制剂治疗挽救了正常加工。内化的R248 C和Y373 C突变体受体，形成稳定的二硫键结合的二聚体在细胞表面的效率低于野生型，而泛素化显着增加，但显然独立的E3泛素连接酶Casitas B系淋巴瘤（c-Cbl）。K650 M突变体对c-Cbl的组成性磷酸化似乎与受体的细胞内滞留有关。因此，尽管影响TK 2结构域的突变K650 M诱导过度磷酸化受体的缺陷性靶向，但影响细胞外结构域和终止密码子的突变导致不同的机制，其特征在于受体保留在质膜上，过度泛素化和降解减少。
Recurrent missense fibroblast growth factor receptor 3 (FGFR3) mutations have been ascribed to skeletal dysplasias of variable severity including the lethal neonatal thanatophoric dysplasia types I (TDI) and II (TDII). To elucidate the role of activating mutations causing TDI on receptor trafficking and endocytosis, a series of four mutants located in different domains of the receptor were generated and transiently expressed. The putatively elongated X807R receptor was identified as three isoforms. The fully glycosylated mature isoform was constitutively but mildly phosphorylated. Similarly, mutations affecting the extracellular domain (R248C and Y373C) induced moderate constitutive receptor phosphorylation. By contrast, the K650M mutation affecting the tyrosine kinase 2 (TK2) domain produced heavy phosphorylation of the nonglycosylated and mannose-rich isoforms that impaired receptor trafficking through the Golgi network. This resulted in defective expression of the mature isoform at the cell surface. Normal processing was rescued by tyrosine kinase inhibitor treatment. Internalization of the R248C and Y373C mutant receptors, which form stable disulfide-bonded dimers at the cell surface was less efficient than the wild-type, whereas ubiquitylation was markedly increased but apparently independent of the E3 ubiquitin-ligase casitas B-lineage lymphoma (c-Cbl). Constitutive phosphorylation of c-Cbl by the K650M mutant appeared to be related to the intracellular retention of the receptor. Therefore, although mutation K650M affecting the TK2 domain induces defective targeting of the overphosphorylated receptor, a different mechanism characterized by receptor retention at the plasma membrane, excessive ubiquitylation and reduced degradation results from mutations that affect the extracellular domain and the stop codon.