Department of Biomedicine, Pharmazentrum, University of Basel, Basel, Switzerland.
Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken, Copenhagen, Denmark.
Elife. 2023 Jan 23;12:e82082. doi: 10.7554/eLife.82082.
Amyloid-β precursor protein (APP) regulates neuronal activity through the release of secreted APP (sAPP) acting at cell surface receptors. APP and sAPP were reported to bind to the extracellular sushi domain 1 (SD1) of GABA receptors (GBRs). A 17 amino acid peptide (APP17) derived from APP was sufficient for SD1 binding and shown to mimic the inhibitory effect of sAPP on neurotransmitter release and neuronal activity. The functional effects of APP17 and sAPP were similar to those of the GBR agonist baclofen and blocked by a GBR antagonist. These experiments led to the proposal that sAPP activates GBRs to exert its neuronal effects. However, whether APP17 and sAPP influence classical GBR signaling pathways in heterologous cells was not analyzed. Here, we confirm that APP17 binds to GBRs with nanomolar affinity. However, biochemical and electrophysiological experiments indicate that APP17 does not influence GBR activity in heterologous cells. Moreover, APP17 did not regulate synaptic GBR localization, GBR-activated K currents, neurotransmitter release, or neuronal activity in vitro or in vivo. Our results show that APP17 is not a functional GBR ligand and indicate that sAPP exerts its neuronal effects through receptors other than GBRs.
淀粉样前体蛋白（APP）通过释放作用于细胞表面受体的分泌型 APP（sAPP）来调节神经元活性。据报道，APP 和 sAPP 与 GABA 受体（GBRs）的细胞外 sushi 结构域 1（SD1）结合。源自 APP 的 17 个氨基酸肽（APP17）足以与 SD1 结合，并显示出模拟 sAPP 对神经递质释放和神经元活性的抑制作用。APP17 和 sAPP 的功能作用与 GBR 激动剂巴氯芬相似，并且被 GBR 拮抗剂阻断。这些实验导致提出 sAPP 通过激活 GBR 发挥其神经元作用。然而，APP17 和 sAPP 是否影响异源细胞中的经典 GBR 信号通路尚未进行分析。在这里，我们证实 APP17 以纳摩尔亲和力结合 GBR。然而，生化和电生理实验表明，APP17 不会影响异源细胞中的 GBR 活性。此外，APP17 并未调节体外或体内突触 GBR 定位、GBR 激活的 K 电流、神经递质释放或神经元活性。我们的结果表明 APP17 不是功能性 GBR 配体，并表明 sAPP 通过除 GBR 以外的受体发挥其神经元作用。
