Proteomic analysis reveals co-ordinated alterations in protein synthesis and degradation pathways in LRRK2 knockout mice

Mutations in leucine-rich repeat kinase 2 (LRRK2) segregate with familial Parkinson’s disease (PD) and genetic variation in LRRK2 contributes to risk of sporadic disease. Although knockout of LRRK2 or knock-in of pathogenic mutations into the mouse germline does not result in a PD phenotype, several defects have been reported in the kidneys of LRRK2 knockout mice. To understand LRRK2 function in vivo, we used an unbiased approach to determine which protein pathways are affected in LRRK2 knockout kidneys. We performed two iTRAQ screens on cytosol- and microsome-enriched fractions from 12-month old LRRK2-KO and G2019S knockin kidneys compared to wild type controls. We nominated changes in cytoskeletal-associated proteins, lysosomal proteases, proteins involved in vesicular trafficking and in control of protein translation in LRRK2-KO. Changes were not seen in mice expressing the pathogenic G2019S LRRK2 mutant.

富亮氨酸重复激酶2（LRRK2）的突变与家族性帕金森病（PD）连锁相关，且LRRK2的遗传变异会增加散发性帕金森病的发病风险。尽管在小鼠生殖系中敲除LRRK2或敲入致病性突变均未引发帕金森病表型，但已有研究报道LRRK2基因敲除小鼠的肾脏存在多种异常。为了在体内解析LRRK2的功能，我们采用无偏筛选方法，探究LRRK2基因敲除小鼠肾脏中受影响的蛋白质通路。我们对12月龄LRRK2敲除（LRRK2-KO）及致病性G2019S敲入小鼠的肾脏的胞浆富集组分与微粒体富集组分，分别开展了两次同位素标记相对和绝对定量（iTRAQ）筛选，并以野生型小鼠作为对照。我们鉴定出LRRK2-KO小鼠肾脏中存在以下改变：细胞骨架相关蛋白、溶酶体蛋白酶、参与囊泡运输及蛋白质翻译调控的蛋白表达异常。而表达致病性G2019S突变LRRK2的小鼠未出现上述改变。