The kinase activity of fibroblast growth factor receptor 3 with activation loop mutations affects receptor trafficking and signaling
The kinase activity of fibroblast growth factor receptor 3 with activation loop mutations affects receptor trafficking and signaling
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DOI：
10.1074/jbc.m405247200
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发表时间：
2004-10-08
影响因子：
4.8
通讯作者：
Liboi, E
中科院分区：
文献类型：
--
作者：
Lievens, PMJ;Mutinelli, C;Liboi, E
成纤维细胞生长因子受体3（FGFR 3）激活环激酶结构域内Lys-650密码子处的氨基酸取代导致受体的分级组成性磷酸化。因此，Lys-650突变体与临床严重程度分级的侏儒症相关。为了评估磷酸化水平对沿着分泌途径的FGFR 3成熟的重要性，研究了血凝素A标记的衍生物。高度活化的SADDAN（严重软骨发育不全伴发育迟缓和黑棘皮病）突变体以其未成熟和磷酸化形式在内质网（ER）中积累，其不能被降解。此外，Janus激酶（Jak）/STAT途径通过Jak 1的直接募集从ER激活。通过替换关键的Tyr-718来消除突变的FGFR 3的自催化性质，重建受体完全成熟并抑制信号传导。因此，低活化软骨发育不全突变体作为成熟的磷酸化形式存在于质膜上，尽管在ER中具有延迟的转变，并且被完全加工。信号传导在布雷菲德菌素A的存在下不发生;相反，当蛋白质分泌被莫能菌素阻断时，STAT 1被激活，这表明软骨发育不良受体在ER的出口处发出信号。我们的研究结果表明，激酶活性影响FGFR 3的运输，并确定信号通路的空间分离。因此，高度活化受体的下调缺陷导致细胞内隔室的信号传导能力增加，这可能决定疾病的严重程度。
Amino acid substitutions at the Lys-650 codon within the activation loop kinase domain of fibroblast growth factor receptor 3 (FGFR3) result in graded constitutive phosphorylation of the receptor. Accordingly, the Lys-650 mutants are associated with dwarfisms with graded clinical severity. To assess the importance of the phosphorylation level on FGFR3 maturation along the secretory pathway, hemagglutinin A-tagged derivatives were studied. The highly activated SADDAN (severe achondroplasia with developmental delay and acanthosis nigricans) mutant accumulates in its immature and phosphorylated form in the endoplasmic reticulum (ER), which fails to be degraded. Furthermore, the Janus kinase (Jak)/STAT pathway is activated from the ER by direct recruitment of Jak1. Abolishing the autocatalytic property of the mutated FGFR3 by replacing the critical Tyr-718 reestablishes the receptor full maturation and inhibits signaling. Differently, the low activated hypochondroplasia mutant is present as a mature phosphorylated form on the plasma membrane, although with a delayed transition in the ER, and is completely processed. Signaling does not occur in the presence of brefeldin A; instead, STAT1 is activated when protein secretion is blocked with monensin, suggesting that the hypochondroplasia receptor signals at the exit from the ER. Our results suggest that kinase activity affects FGFR3 trafficking and determines the spatial segregation of signaling pathways. Consequently, the defect in down-regulation of the highly activated receptors results in the increased signaling capacity from the intracellular compartments, and this may determine the severity of the diseases.