Kaneko Aoi, Kiryu-Seo Sumiko, Matsumoto Sakiko, Kiyama Hiroshi
Department of Functional Anatomy and Neuroscience, Graduate School of Medicine, Nagoya University, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
Cell Death Dis. 2017 Jun 1;8(6):e2847. doi: 10.1038/cddis.2017.212.
Damage-induced neuronal endopeptidase (DINE)/endothelin-converting enzyme-like 1 (ECEL1) is a membrane-bound metalloprotease that we identified as a nerve regeneration-associated molecule. The expression of DINE is upregulated in response to nerve injury in both the peripheral and central nervous systems, while its transcription is regulated by the activating transcription factor 3 (ATF3), a potent hub-transcription factor for nerve regeneration. Despite its unique hallmark of injury-induced upregulation, the physiological relevance of DINE in injured neurons has been unclear. In this study, we have demonstrated that the expression of DINE is upregulated in injured retinal ganglion cells (RGCs) in a coordinated manner with that of ATF3 after optic nerve injury, whereas DINE and ATF3 are not observed in any normal retinal cells. Recently, we have generated a mature DINE-deficient (KO) mouse, in which exogenous DINE is overexpressed specifically in embryonic motor neurons to avoid aberrant arborization of motor nerves and lethality after birth that occurs in the conventional DINE KO mouse. The DINE KO mice did not show any difference in retinal structure and the projection to brain from that of wild-type (wild type) mice under normal conditions. However, injured RGCs of DINE KO mice failed to regenerate even after the zymosan treatment, which is a well-known regeneration-promoting reagent. Furthermore, a DINE KO mouse crossed with a Atf3:BAC Tg mouse, in which green fluorescent protein (GFP) is visualized specifically in injured RGCs and optic nerves, has verified that DINE deficiency leads to regeneration failure. These findings suggest that injury-induced DINE is a crucial endopeptidase for injured RGCs to promote axonal regeneration after optic nerve injury. Thus, a DINE-mediated proteolytic mechanism would provide us with a new therapeutic strategy for nerve regeneration.
损伤诱导神经元内肽酶（DINE）/内皮素转换酶样1（ECEL1）是一种膜结合金属蛋白酶，我们将其鉴定为一种与神经再生相关的分子。在周围和中枢神经系统中，DINE的表达在神经损伤后均上调，而其转录受激活转录因子3（ATF3）调控，ATF3是神经再生的一种重要枢纽转录因子。尽管DINE具有损伤诱导上调这一独特特征，但其在受损神经元中的生理相关性尚不清楚。在本研究中，我们证明视神经损伤后，损伤的视网膜神经节细胞（RGC）中DINE的表达与ATF3的表达协同上调，而在任何正常视网膜细胞中均未观察到DINE和ATF3。最近，我们培育出了一种成熟的DINE缺陷（KO）小鼠，其中外源性DINE在胚胎运动神经元中特异性过表达，以避免运动神经异常分支以及传统DINE KO小鼠出生后出现的致死性。在正常条件下，DINE KO小鼠的视网膜结构以及向脑内的投射与野生型小鼠相比没有任何差异。然而，即使经过酵母聚糖处理（一种众所周知的促进再生的试剂），DINE KO小鼠受损的RGC仍无法再生。此外，将DINE KO小鼠与Atf3:BAC Tg小鼠杂交，在Atf3:BAC Tg小鼠中绿色荧光蛋白（GFP）在受损的RGC和视神经中特异性可视化，这证实了DINE缺陷导致再生失败。这些发现表明，损伤诱导的DINE是受损RGC在视神经损伤后促进轴突再生的关键内肽酶。因此，DINE介导的蛋白水解机制将为我们提供一种新的神经再生治疗策略。
