Duval Nathan, Sumner Whitney A, Andrianakos Anna G, Gray Josie J, Bouchard Ron J, Wilkins Heather M, Linseman Daniel A
Biological Sciences and Knoebel Institute for Healthy Aging, University of Denver, Denver, CO, United States.
Biological Sciences and Eleanor Roosevelt Institute, University of Denver, Denver, CO, United States.
Front Cell Neurosci. 2018 Jan 30;12:15. doi: 10.3389/fncel.2018.00015. eCollection 2018.
The molecular mechanisms leading to motor neuron death in amyotrophic lateral sclerosis (ALS) are unknown; however, several studies have provided evidence of a central role for intrinsic apoptosis. Bcl-2 homology-3 domain (BH3)-only proteins are pro-apoptotic members of the Bcl-2 family whose enhanced expression acts as a trigger for the intrinsic apoptotic cascade. Here, we compared the relative expression of BH3-only proteins in the spinal cord of end-stage G93A mutant SOD1 mice to age-matched wild-type (WT) mice. Large alpha motor neurons in lumbar spinal cord sections of both WT and end-stage mutant SOD1 mice stained positively for a number of BH3-only proteins; however, no discernible differences were observed in either the relative intensity of staining or number of BH3-immunoreactive motor neurons between WT and mutant SOD1 mice. On the other hand, we observed significantly enhanced staining for Bid, DP5/Hrk, and BNip3L in GFAP-positive astrocytes only in end-stage G93A mutant SOD1 spinal cord. Staining of additional end-stage G93A mutant SOD1 tissues showed specific upregulation of DP5/Hrk in lumbar spinal cord sections, but not in cerebellum or cortex. Finally, examination of protein expression using western blotting also revealed marked increases in DP5/Hrk and BNip3L in G93A mutant SOD1 lumbar spinal cord lysates compared to WT controls. The upregulation of a specific subset of BH3-only proteins, including Bid, DP5/Hrk, and BNip3L, in reactive astrocytes suggests that these proteins may execute a novel function within astrocytes to promote ALS disease progression, thus providing a new potential target for therapeutic intervention.
导致肌萎缩侧索硬化症（ALS）运动神经元死亡的分子机制尚不清楚；然而，多项研究已提供证据表明内源性凋亡起核心作用。仅含Bcl-2同源结构域3（BH3）的蛋白是Bcl-2家族的促凋亡成员，其表达增强可触发内源性凋亡级联反应。在此，我们比较了终末期G93A突变SOD1小鼠与年龄匹配的野生型（WT）小鼠脊髓中仅含BH3蛋白的相对表达。WT小鼠和终末期突变SOD1小鼠腰段脊髓切片中的大型α运动神经元对多种仅含BH3的蛋白呈阳性染色；然而，在WT小鼠和突变SOD1小鼠之间，染色的相对强度或BH3免疫反应性运动神经元的数量均未观察到明显差异。另一方面，我们仅在终末期G93A突变SOD1脊髓的GFAP阳性星形胶质细胞中观察到Bid、DP5/Hrk和BNip3L的染色显著增强。对其他终末期G93A突变SOD1组织的染色显示，腰段脊髓切片中DP5/Hrk有特异性上调，但在小脑或皮质中未上调。最后，使用蛋白质印迹法检测蛋白表达也显示，与WT对照相比，G93A突变SOD1小鼠腰段脊髓裂解物中DP5/Hrk和BNip3L明显增加。反应性星形胶质细胞中包括Bid、DP5/Hrk和BNip3L在内的特定仅含BH3蛋白亚群的上调表明，这些蛋白可能在星形胶质细胞内执行新功能以促进ALS疾病进展，从而为治疗干预提供了新的潜在靶点。
