Ataxin-3的亚细胞定位及其对细胞器形态的影响

摘要

Objective To explore the subcellular localization of ataxin-3 and the effect of polyglutamine (polyQ) expansion mutation on the morphology of mitochondrion,golgi apparatus and endoplasmic reticulum.Methods Transient transfeetion was employed to build cell models expressing wildtype or mutant ataxin-3 proteins.Indirect immunofluorescence was applied to identify markers of organelle membrane.The results were observed under a laser scanning confocal microscope.Results No colocalization was observed for ataxin-3 protein and mitochondrial marker TOM20,but the percentage of cells with mitochondrial fragmentation has increased in cells expressing mutant ataxin-3 (P＜ 0.05).No colocalization was observed for ataxin-3 protein and golgi marker GM130,and mutant ataxin-3 did not cause golgi fragmentation.Wide type and polyQ-expanded ataxin-3 both showed partial co-localization with ER marker calnexin.The latter showed more overlap with calnexin,and the overlapping signals were mostly located in the places where aggregates were situated.Conclusion PolyQ-expanded ataxin-3 protein may indirectly affect the integrity of mitochondria,but may cause no effect on the structure and functions of golgi apparatus.Endoplasmic reticulum may be another place where extended ataxin-3 protein can induce cytotoxicity in addition to the nucleus.%目的 探讨ataxin-3蛋白的亚细胞定位及其多聚谷氨酰胺(polyglutamine,polyQ)扩展突变对线粒体、高尔基体和内质网形态的影响.方法 采用瞬时转染法构建表达野生型和突变型ataxin-3蛋白的细胞模型,用间接免疫荧光法识别细胞器膜的标记蛋白,在激光共聚焦显微镜下观察.结果 ataxin-3与TOM20无共定位,但突变组线粒体碎裂细胞百分比增加(P＜0.05);ataxin-3与GM130无共定位且突变组无高尔基体碎裂;ataxin-3与calnexin部分共定位,突变组重叠信号较多且大多位于聚集体所在处.结论 polyQ扩展型ataxin-3蛋白可能间接损害线粒体完整性但并不影响高尔基体的结构和功能,而内质网可能是扩展型ataxin-3蛋白在细胞核外发挥毒性作用的场所.