Zhai Jinbin, Lin Hong, Canete-Soler Rafaela, Schlaepfer William W
Division of Neuropathology, Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Hum Mol Genet. 2005 Sep 15;14(18):2629-40. doi: 10.1093/hmg/ddi297. Epub 2005 Aug 3.
Mutations in Cu/Zn superoxide dismutase (SOD1) cause approximately 20% of familial amyotrophic lateral sclerosis by a toxic gain of function; however, the precise mechanisms remain unclear. Here, we report the identification of HoxB2, a homeodomain-containing transcription factor, as a G93A mutant SOD1 interactive protein in a yeast two-hybrid screen. We show that HoxB2 co-precipitates and co-localizes with mutant SOD1 in neuronal cell lines, as well as in brain and spinal cord of G93A mutant SOD1 transgenic mice. Mutagenesis further shows that this interaction is mediated by the central homeodomain of HoxB2. In motor neuron-like NSC-34 cells, overexpression of HoxB2 or its homeodomain decreases the insolubility of mutant SOD1 and inhibits G93A or G86R mutant SOD1-induced neuronal cell death. In human and mouse tissues, we show that expression of HoxB2 persists in adult spinal cord and is primarily localized in nuclei of motor neurons. In G93A transgenic mice, HoxB2 co-localizes with mutant SOD1 and is redistributed to perikarya and proximal neurites of motor neurons. In addition, there is progressive accumulation of HoxB2 and mutant SOD1 as punctate inclusions in the neuropil surrounding motor neurons. Taken together, our findings demonstrate that interaction of HoxB2 with mutant SOD1 occurs in motor neurons of G93A mutant SOD1 transgenic mice and suggest that this interaction may modulate the neurotoxicity of mutant SOD1.
铜锌超氧化物歧化酶（SOD1）的突变通过功能获得性毒性作用导致约20%的家族性肌萎缩侧索硬化症；然而，确切机制仍不清楚。在此，我们报告在酵母双杂交筛选中鉴定出含同源结构域的转录因子HoxB2为G93A突变型SOD1相互作用蛋白。我们发现，在神经元细胞系以及G93A突变型SOD1转基因小鼠的脑和脊髓中，HoxB2与突变型SOD1共沉淀并共定位。诱变进一步表明，这种相互作用由HoxB2的中央同源结构域介导。在运动神经元样NSC-34细胞中，HoxB2或其同源结构域的过表达降低了突变型SOD1的不溶性，并抑制了G93A或G86R突变型SOD1诱导的神经元细胞死亡。在人和小鼠组织中，我们发现HoxB2在成年脊髓中持续表达，且主要定位于运动神经元的细胞核。在G93A转基因小鼠中，HoxB2与突变型SOD1共定位，并重新分布到运动神经元的胞体和近端神经突。此外，HoxB2和突变型SOD1作为点状包涵体在运动神经元周围的神经毡中逐渐积累。综上所述，我们的研究结果表明，HoxB2与突变型SOD1的相互作用发生在G93A突变型SOD1转基因小鼠的运动神经元中，并提示这种相互作用可能调节突变型SOD1的神经毒性。
