The transmembrane mutation G380R in fibroblast growth factor receptor 3 uncouples ligand-mediated receptor activation from down-regulation
The transmembrane mutation G380R in fibroblast growth factor receptor 3 uncouples ligand-mediated receptor activation from down-regulation
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DOI：
10.1128/mcb.20.2.516-522.2000
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发表时间：
2000-01-01
影响因子：
5.3
通讯作者：
Yayon, A
中科院分区：
文献类型：
--
作者：
Monsonego-Ornan, E;Adar, R;Yayon, A
成纤维细胞生长因子受体3(FGFR3)跨膜区的Gly380Arg点突变会导致软骨发育不全，这是人类最常见的遗传性侏儒症。这种替换被认为可以增强突变受体的二聚化，导致结构性的、非配体依赖的激活。我们发现G380R突变受体的二聚化和激活主要依赖于配体。然而，使用瞬时和稳定的转染法，我们发现只有突变的受体蛋白有显著的过度表达。代谢脉冲追逐实验、细胞表面标记和放射性标记配体的摄取动力学表明，突变受体的下调具有选择性的延迟。此外，这种受体现在对配体介导的内化具有抵抗力，即使在饱和的配体浓度下也是如此。最后，在小鼠受体转录控制下表达人G380R突变受体的转基因小鼠，其骨骺生长板内FGFR3免疫反应性区域显著扩大，与体内受体下调的缺陷相一致。我们认为，软骨发育不全突变G380R在FGFR3信号的水平和动力学对软骨细胞成熟和骨形成至关重要的位置解除了配体介导的受体激活的下调。
A point mutation, Gly380Arg, in the transmembrane domain of fibroblast growth factor receptor 3 (FGFR3) leads to achondroplasia, the most common form of genetic dwarfism in humans. This substitution was suggested to enhance mutant receptor dimerization, leading to constitutive, ligand-independent activation. We found that dimerization and activation of the G380R mutant receptor are predominantly ligand dependent. However, using both transient and stable transfections, we found significant overexpression only of the mutant receptor protein. Metabolic pulse-chase experiments, cell surface labeling, and kinetics of uptake of radiolabeled ligand demonstrated a selective delay in the down-regulation of the mutant receptor. Moreover, this receptor was now resistant to ligand-mediated internalization, even at saturating ligand concentrations. Finally, transgenic mice expressing the human G380R mutant receptor under the mouse receptor transcriptional control demonstrated a markedly expanded area of FGFR3 immunoreactivity within their epiphyseal growth plates, compatible with an in vivo defect in receptor down-regulation. We propose that the achondroplasia mutation G380R uncouples ligand-mediated receptor activation from down-regulation at a site where the levels and kinetics of FGFR3 signals are crucial for chondrocyte maturation and bone formation.