The Ras-GTPase activity of neurofibromin restrains ERK-dependent FGFR signaling during endochondral bone formation
The Ras-GTPase activity of neurofibromin restrains ERK-dependent FGFR signaling during endochondral bone formation
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DOI：
10.1093/hmg/ddt162
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发表时间：
2013-08-01
影响因子：
3.5
通讯作者：
Elefteriou, Florent
中科院分区：
文献类型：
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作者：
Ono, Koichiro;Karolak, Matthew R.;Elefteriou, Florent
由软骨细胞外信号调节蛋白激酶1和2(ERK1/2)的获得或丧失导致的生长板发育的严重缺陷表明，严格的空间和时间调控丝裂原激活的蛋白激酶信号对于实现生长板的协调伸长和结构是必要的。我们提供的证据表明，神经纤维素通过其RAS鸟苷三磷酸酶激活活性，控制软骨细胞中ERK1/2依赖的成纤维细胞生长因子受体(FGFR)信号。我们首先表明，在生长板软骨内骨化过程中，神经纤维蛋白在FGFR阳性的肥大前期和肥大软骨细胞中表达。利用II型胶原表达细胞中缺乏神经纤维蛋白1(NF1)的小鼠(NF1(Col2)(/)突变小鼠)，我们随后发现有丝分裂后软骨细胞中缺乏神经纤维蛋白会触发许多表型，这些表型让人想起以FGFR功能获得突变为特征的小鼠的表型。这些包括侏儒症，结构性ERK1/2激活，IHH表达显著降低，软骨细胞增殖和成熟减少，软骨细胞RANKL、基质金属蛋白酶9(MMP9)和MMP13表达增加，生长板破骨细胞生成增强，以及对caspase-9介导的细胞凋亡的敏感性增加。使用野生型(WT)和NF1(/)软骨细胞体外培养，我们发现FGF2脉冲刺激在这两种类型的软骨细胞中都能迅速触发ERK1/2磷酸化，但在NF1(/)软骨细胞中恢复到基础水平的时间被推迟。重要的是，在体内，通过每天给出生后的幼鼠注射重组形式的C型利钠肽18天来抑制ERK1/2，能够纠正NF1(Col2)(/)小鼠的矮小身材。综上所述，这些结果强调了神经纤维素和ERK1/2对正常软骨内骨形成的要求，并支持神经纤维素通过抑制Ras-ERK1/2信号通路在软骨细胞分化过程中是FGFR信号的负调节因子的观点。
The severe defects in growth plate development caused by chondrocyte extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) gain or loss-of-function suggest that tight spatial and temporal regulation of mitogen-activated protein kinase signaling is necessary to achieve harmonious growth plate elongation and structure. We provide here evidence that neurofibromin, via its Ras guanosine triphosphatase -activating activity, controls ERK1/2-dependent fibroblast growth factor receptor (FGFR) signaling in chondrocytes. We show first that neurofibromin is expressed in FGFR-positive prehypertrophic and hypertrophic chondrocytes during growth plate endochondral ossification. Using mice lacking neurofibromin 1 (Nf1) in type II collagen-expressing cells, (Nf1(col2)(/) mutant mice), we then show that lack of neurofibromin in post-mitotic chondrocytes triggers a number of phenotypes reminiscent of the ones observed in mice characterized by FGFR gain-of-function mutations. Those include dwarfism, constitutive ERK1/2 activation, strongly reduced Ihh expression and decreased chondrocyte proliferation and maturation, increased chondrocytic expression of Rankl, matrix metalloproteinase 9 (Mmp9) and Mmp13 and enhanced growth plate osteoclastogenesis, as well as increased sensitivity to caspase-9 mediated apoptosis. Using wildtype (WT) and Nf1(/) chondrocyte cultures in vitro, we show that FGF2 pulse-stimulation triggers rapid ERK1/2 phosphorylation in both genotypes, but that return to the basal level is delayed in Nf1(/) chondrocytes. Importantly, in vivo ERK1/2 inhibition by daily injection of a recombinant form of C-type natriuretic peptide to post-natal pups for 18 days was able to correct the short stature of Nf1(col2)(/) mice. Together, these results underscore the requirement of neurofibromin and ERK1/2 for normal endochondral bone formation and support the notion that neurofibromin, by restraining RAS-ERK1/2 signaling, is a negative regulator of FGFR signaling in differentiating chondrocytes.