GRK5 Deficiency Leads to Reduced Hippocampal Acetylcholine Level via Impaired Presynaptic M2/M4 Autoreceptor Desensitization
GRK5 Deficiency Leads to Reduced Hippocampal Acetylcholine Level via Impaired Presynaptic M2/M4 Autoreceptor Desensitization
复制标题
GRK5 缺乏通过突触前 M2/M4 自身受体脱敏受损导致海马乙酰胆碱水平降低
DOI：
10.1074/jbc.m109.005959
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发表时间：
2009-07-17
影响因子：
4.8
通讯作者：
Suo, William Z.
中科院分区：
文献类型：
--
作者：
Liu, Jun;Rasul, Imtiaz;Suo, William Z.
G蛋白偶联受体激酶5（GRK 5）缺陷最近已被链接到早期阿尔茨海默病（AD），但GRK 5缺陷可能有助于AD发病机制仍然是难以捉摸的。在这里，我们报告，在胆碱能神经元细胞系中过表达GRK 5（dnGRK 5）的显性负突变体导致乙酰胆碱（ACh）释放减少。百日咳毒素、阿托品（一种非选择性毒蕈碱拮抗剂）或甲氧四明（一种选择性M2/M4毒蕈碱受体拮抗剂）可完全纠正这种减少。与培养细胞中的结果一致，年轻GRK 5基因敲除小鼠海马切片中高钾诱发的ACh释放与野生型同窝仔相比显着减少，并且这种减少的ACh释放也完全由甲氧四明纠正。此外，治疗后与非选择性毒蕈碱激动剂oxotremorine-M，M2和M4受体经历了显着减少的内化GRK 5 KO切片与野生型切片相比，评估质膜保留受体免疫反应性，而M1受体内化不受GRK 5表达的损失。此外，蛋白质印迹法显示年轻GRK 5基因敲除小鼠没有突触或胆碱能退行性变化。总之，这些结果表明，GRK 5缺陷导致减少海马ACh释放和胆碱能功能减退的选择性损害的脱敏突触前M2/M4的自身受体。由于这种非结构性胆碱能功能减退先于海马胆碱能功能减退，海马胆碱能功能减退与老年GRK 5基因敲除小鼠的结构性胆碱能变性和认知能力下降相关，这种非结构性改变可能是导致AD胆碱能变性的早期事件。
G protein-coupled receptor kinase 5 (GRK5) deficiency has been linked recently to early Alzheimer disease (AD), but the mechanism by which GRK5 deficiency may contribute to AD pathogenesis remains elusive. Here we report that overexpression of dominant negative mutant of GRK5 (dnGRK5) in a cholinergic neuronal cell line led to decreased acetylcholine (ACh) release. This reduction was fully corrected by pertussis toxin, atropine (a nonselective muscarinic antagonist), or methoctramine(a selective M2/M4 muscarinic receptor antagonist). Consistent with results in cultured cells, high potassium-evoked ACh release in hippocampal slices from young GRK5 knock-out mice was significantly reduced compared with wild type littermates, and this reduced ACh release was also fully corrected by methoctramine. In addition, following treatment with the nonselective muscarinic agonist oxotremorine-M, M2, and M4 receptors underwent significantly reduced internalization in GRK5KO slices compared with wild type slices, as assessed by plasma membrane retention of receptor immunoreactivity, whereas M1 receptor internalization was not affected by loss of GRK5 expression. Moreover, Western blotting revealed no synaptic or cholinergic degenerative changes in young GRK5 knock-out mice. Altogether, these results suggest that GRK5 deficiency leads to a reduced hippocampal ACh release and cholinergic hypofunction by selective impairment of desensitization of presynaptic M2/M4 autoreceptors. Because this nonstructural cholinergic hypofunction precedes the hippocampal cholinergic hypofunction associated with structural cholinergic degeneration and cognitive decline in aged GRK5 knock-out mice, this nonstructural alteration may be an early event contributing to cholinergic degeneration in AD.