APP modulates KCC2 expression and function in hippocampal GABAergic inhibition
APP modulates KCC2 expression and function in hippocampal GABAergic inhibition
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DOI：
10.7554/elife.20142
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发表时间：
2017-01-05
期刊：
影响因子：
7.7
通讯作者：
Yang, Li
中科院分区：
文献类型：
--
作者：
Chen, Ming;Wang, Jinzhao;Yang, Li
淀粉样前体蛋白(APP)在突触处丰富，但其突触功能仍知之甚少。我们之前的研究表明，在App基因敲除(App(-/-))动物中，GABA能的短期可塑性受到损害，但APP调节GABA能突触传递的确切机制仍不清楚。通过电生理、生化、分子生物学和药理学分析，我们证明了APP可以与KCC2相互作用，KCC2是一种神经元特异性的K+-Cl-共转运体，对Cl-稳态和快速GABA能抑制是必不可少的。APP缺乏导致总KCC2水平和膜KCC2水平的显著降低，导致GABA反转电位(EGABA)的去极化移动。对海马神经元突触前动作电位和抑制性突触后电流(IPSCs)的同时测量显示，GABAAR A1亚单位水平的降低可导致IPSC幅值的损害。重要的是，在App(-/-)小鼠中恢复正常的KCC2表达和功能可以挽救E-GABA、GABA(A)Rα1水平和GABA(A)R介导的时相抑制。我们发现，APP能够限制酪氨酸磷酸化和泛素化，从而限制KCC2的随后降解，从而提供了APP影响KCC2丰度的机制。总之，这些实验阐明了APP通过蛋白质与KCC2的相互作用来调节海马区GABA(A)R介导的抑制的一种新的分子途径。
Amyloid precursor protein (APP) is enriched at the synapse, but its synaptic function is still poorly understood. We previously showed that GABAergic short-term plasticity is impaired in App knock-out (App(-/-)) animals, but the precise mechanism by which APP regulates GABAergic synaptic transmission has remained elusive. Using electrophysiological, biochemical, moleculobiological, and pharmacological analysis, here we show that APP can physically interact with KCC2, a neuron-specific K+-Cl- cotransporter that is essential for Cl- homeostasis and fast GABAergic inhibition. APP deficiency results in significant reductions in both total and membrane KCC2 levels, leading to a depolarizing shift in the GABA reversal potential (EGABA). Simultaneous measurement of presynaptic action potentials and inhibitory postsynaptic currents (IPSCs) in hippocampal neurons reveals impaired unitary IPSC amplitudes attributable to a reduction in a1 subunit levels of GABAAR. Importantly, restoration of normal KCC2 expression and function in App(-/-) mice rescues E-GABA, GABA(A)R alpha 1 levels and GABA(A)R mediated phasic inhibition. We show that APP functions to limit tyrosine-phosphorylation and ubiquitination and thus subsequent degradation of KCC2, providing a mechanism by which APP influences KCC2 abundance. Together, these experiments elucidate a novel molecular pathway in which APP regulates, via protein-protein interaction with KCC2, GABA(A)R mediated inhibition in the hippocampus.