Waragai Masaaki, Nagamitsu Shinichiro, Xu Weidong, Li Yu Jiang, Lin Xi, Ashizawa Tetsuo
Department of Neurology, University of Texas Medical Branch, Galveston, Texas 77555-0539, USA.
J Neurosci Res. 2006 May 15;83(7):1170-8. doi: 10.1002/jnr.20807.
Spinocerebellar ataxia type 10 (SCA10) is a dominantly inherited disorder caused by an intronic ATTCT pentanucleotide repeat expansion. The ATXN10 gene encodes a novel protein, ataxin 10, known previously as E46L, which is widely expressed in the brain. Ataxin 10 deficiency has been shown recently to cause increased apoptosis in primary cerebellar cultures, thus implicated in SCA10 pathogenesis. The biologic functions of ataxin 10 remain largely unknown. By using yeast-two-hybrid screening of a human brain cDNA library, we identified the G-protein beta2 subunit (Gbeta2) as an ataxin 10 binding partner, and the interaction was confirmed by coimmunoprecipitation and colocalization in mammalian cells in culture. Overexpression of ataxin 10 in PC12 cells induced neurite extension and enhanced neuronal differentiation induced by nerve growth factor (NGF). Moreover, coexpression of ataxin 10 and Gbeta2 potently activated the Ras-MAP kinase-Elk-1 cascade. Dominant negative Ras or inhibitor of MEK-1/2 (U0126) aborted this activation, and blocked morphologic changes, whereas inhibition of TrkA receptor by K252a had no effects. Our data suggest that the ataxin 10-Gbeta2 interaction represents a novel mechanism for inducing neuritogenesis in PC12 cells by activating the Ras-MAP kinase-Elk-1 cascade.
10型脊髓小脑共济失调（SCA10）是一种由内含子ATTCT五核苷酸重复序列扩增引起的常染色体显性遗传疾病。ATXN10基因编码一种新的蛋白质，即共济失调蛋白10，以前称为E46L，它在大脑中广泛表达。最近研究表明，共济失调蛋白10缺乏会导致原代小脑培养物中细胞凋亡增加，因此与SCA10的发病机制有关。共济失调蛋白10的生物学功能在很大程度上仍然未知。通过利用人脑cDNA文库进行酵母双杂交筛选，我们鉴定出G蛋白β2亚基（Gbeta2）是共济失调蛋白10的结合伴侣，并且通过共免疫沉淀和在培养的哺乳动物细胞中的共定位证实了这种相互作用。在PC12细胞中过表达共济失调蛋白10可诱导神经突延伸，并增强神经生长因子（NGF）诱导的神经元分化。此外，共济失调蛋白10和Gbeta2的共表达可有效激活Ras-MAP激酶-Elk-1级联反应。显性负性Ras或MEK-1/2抑制剂（U0126）可终止这种激活，并阻断形态学变化，而K252a对TrkA受体的抑制则没有影响。我们的数据表明，共济失调蛋白10-Gbeta2相互作用代表了一种通过激活Ras-MAP激酶-Elk-1级联反应在PC12细胞中诱导神经突形成的新机制。
