阿尔茨海默病(AD)的特征是淀粉样蛋白斑块中淀粉样蛋白β(Aβ)的细胞外沉积以及神经原纤维缠结(NFT)中过度磷酸化tau的细胞内聚集和积累。尽管已经确定了几种激酶有助于tau的病理磷酸化,针对AD的激酶靶向治疗在临床试验中尚未成功.严重的,负责许多确定的tau磷酸化位点的激酶仍然未知。G蛋白偶联受体(GPCR)激酶(GRKs)最近与非GPCR底物的磷酸化有关。例如,微管蛋白和α-突触核蛋白,在神经系统疾病中,包括精神分裂症和帕金森病。因此,我们研究了GRKs在AD病理生理学中的参与。
我们对广泛表达的GRKs进行了全面的免疫组织化学和生化分析,即,对照受试者和AD患者的死后人脑组织中的GRK2、3、5和6。
GRKs在神经元中显示出独特的细胞类型特异性表达模式,星形胶质细胞和小胶质细胞。在AD海马的CA1区域中,GRKs2、5和6的水平特异性降低。生化证据表明,GRKs与总量有区别联系,AD脑中的可溶性和不溶性tau库。补充免疫组织化学研究表明,GRKs与总tau差异共定位,磷酸化tau和NFT。值得注意的是,GRKs3和5也与淀粉样蛋白斑共同定位。
这些研究建立了GRK与AD大脑中tau和淀粉样蛋白病理学的病理磷酸化和积累之间的联系,并提示了这些激酶在AD病理标志调节中的新作用。
Alzheimer\'s disease (AD) is characterised by extracellular deposition of amyloid-β (Aβ) in amyloid plaques and intracellular aggregation and accumulation of hyperphosphorylated tau in neurofibrillary tangles (NFTs). Although several kinases have been identified to contribute to the pathological phosphorylation of tau, kinase-targeted therapies for AD have not been successful in clinical trials. Critically, the kinases responsible for numerous identified tau phosphorylation sites remain unknown. G protein-coupled receptor (GPCR) kinases (GRKs) have recently been implicated in phosphorylation of non-GPCR substrates, for example, tubulin and α-synuclein, and in neurological disorders, including schizophrenia and Parkinson\'s disease. Accordingly, we investigated the involvement of GRKs in the pathophysiology of AD.
We performed a comprehensive immunohistochemical and biochemical analysis of the ubiquitously expressed GRKs, namely, GRK2, 3, 5 and 6, in postmortem human brain tissue of control subjects and AD patients.
GRKs display unique cell-type-specific expression patterns in neurons, astrocytes and microglia. Levels of GRKs 2, 5 and 6 are specifically decreased in the CA1 region of the AD hippocampus. Biochemical evidence indicates that the GRKs differentially associate with total, soluble and insoluble pools of tau in the AD brain. Complementary immunohistochemical studies indicate that the GRKs differentially colocalise with total tau, phosphorylated tau and NFTs. Notably, GRKs 3 and 5 also colocalise with amyloid plaques.
These studies establish a link between GRKs and the pathological phosphorylation and accumulation of tau and amyloid pathology in AD brains and suggest a novel role for these kinases in regulation of the pathological hallmarks of AD.