Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain.
Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain; Institut de Neurociències, Department of Biochemistry and Molecular Biology, Universitat Autònoma de Barcelona, Bellaterra, Spain.
Neurobiol Dis. 2019 Apr;124:428-438. doi: 10.1016/j.nbd.2018.12.021. Epub 2018 Dec 27.
ErbB4 is a transmembrane receptor tyrosine kinase that binds to neuregulins to activate signaling. Proteolytic cleavage of ErbB4 results in release of soluble fragments of ErbB4 into the interstitial fluid. Disruption of the neuregulin-ErbB4 pathway has been suggested to be involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). This study assesses whether soluble proteolytic fragments of the ErbB4 ectodomain (ecto-ErbB4) can be detected in cerebrospinal fluid (CSF) and plasma, and if the levels are altered in ALS. Immunoprecipitation combined with mass spectrometry or western blotting analyses confirmed the presence of ecto-ErbB4 in human CSF. Several anti-ErbB4-reactive bands, including a 55 kDa fragment, were detected in CSF. The bands were generated in the presence of neuregulin-1 (Nrg1) and were absent in plasma from ErbB4 knockout mice. Ecto-ErbB4 levels were decreased in CSF from ALS patients (n = 20) and ALS with concomitant frontotemporal dementia patients (n = 10), compared to age-matched controls (n = 13). A similar decrease was found for the short ecto-ErbB4 fragments in plasma of the same subjects. Likewise, the 55-kDa ecto-ErbB4 fragments were decreased in the plasma of the two transgenic mouse models of ALS (SOD1 and TDP-43). Intracellular ErbB4 fragments were decreased in the frontal cortex from SOD1 mice, indicating a reduction in Nrg-dependent induction of ErbB4 proteolytic processing, and suggesting impaired signaling. Accordingly, overexpression of Nrg1 induced by an adeno-associated viral vector increased the levels of the ecto-ErbB4 fragment in the SOD1 mice. We conclude that the determination of circulating ecto-ErbB4 fragments could be a tool to evaluate the impairment of the ErbB4 pathway and may be a useful biomarker in ALS.
ErbB4 是一种跨膜受体酪氨酸激酶,它与神经调节蛋白结合以激活信号。ErbB4 的蛋白水解切割导致 ErbB4 的可溶性片段释放到细胞间质液中。神经调节蛋白-ErbB4 途径的破坏被认为与肌萎缩侧索硬化症 (ALS) 的发病机制有关。本研究评估了可溶性 ErbB4 细胞外结构域 (ecto-ErbB4) 片段是否可以在脑脊液 (CSF) 和血浆中检测到,以及它们在 ALS 中的水平是否发生改变。免疫沉淀结合质谱或 Western blot 分析证实了人 CSF 中存在 ecto-ErbB4。在 CSF 中检测到几种抗 ErbB4 反应性带,包括 55 kDa 片段。这些带是在神经调节蛋白 1 (Nrg1) 的存在下产生的,并且在 ErbB4 敲除小鼠的血浆中不存在。与年龄匹配的对照组 (n=13) 相比,ALS 患者 (n=20) 和伴有额颞叶痴呆的 ALS 患者 (n=10) 的 CSF 中的 ecto-ErbB4 水平降低。在相同受试者的血浆中也发现了短的 ecto-ErbB4 片段的类似减少。同样,在两种 ALS 的转基因小鼠模型 (SOD1 和 TDP-43) 的血浆中,55 kDa 的 ecto-ErbB4 片段减少。SOD1 小鼠的额皮质中细胞内 ErbB4 片段减少,表明 Nrg 依赖性诱导 ErbB4 蛋白水解加工减少,提示信号转导受损。因此,腺相关病毒载体诱导的 Nrg1 的过表达增加了 SOD1 小鼠中 ecto-ErbB4 片段的水平。我们得出结论,循环 ecto-ErbB4 片段的测定可能是评估 ErbB4 途径损伤的一种工具,并且可能是 ALS 中的一种有用的生物标志物。