G protein-gated, inwardly rectifying, potassium (GIRK) channels are important regulators of cellular excitability throughout the body. GIRK channels are heterotetrameric and homotetrameric combinations of the Kir3.1-4 (GIRK1-4) subunits. Different subunit combinations are expressed throughout the central nervous system (CNS) and the periphery, and most of these combinations contain a GIRK1 subunit. For example, the predominance of GIRK channels in the CNS are composed of GIRK1 and GIRK2 subunits, while the GIRK channels in cardiac atrial myocytes are made up mostly of GIRK1 and GIRK4 subunits. Although the vast majority of GIRK channels contain a GIRK1 subunit, discrete populations of cells that express non-GIRK1-containing GIRK (non-GIRK1/X) channels do exist. For instance, dopaminergic neurons in the ventral tegmental area of the brain, associated with addiction and reward, do not express the GIRK1 subunit. Targeting these non-GIRK1/X channels with subunit-selective pharmacological probes could lead to important insights into how GIRK channels are involved in reward and addiction. Such insights may, in turn, reveal therapeutic opportunities for the treatment or prevention of addiction. Previously, our laboratory discovered small molecules that can specifically modulate the activity of GIRK1-containing GIRK channels. However, efforts to generate compounds active on non-GIRK1/X channels from these scaffolds have been unsuccessful. Recently, ivermectin was shown to modulate non-GIRK1/X channels, and historically, ivermectin is known to modulate a wide variety of neuronal channels and receptors. Further, ivermectin is a complex natural product, which makes it a challenging starting point for development of more selective, effective, and potent compounds. Thus, while ivermectin provides proof-of-concept as a non-GIRK1/X channel activator, it is of limited utility. Therefore, we sought to discover a synthetic small molecule that would serve as a starting point for the development of non-GIRK1/X channel modulators. To accomplish this, we used a high-throughput thallium flux assay to screen a 100 000-compound library in search of activators of homomeric GIRK2 channels. Using this approach, we discovered VU0529331, the first synthetic small molecule reported to activate non-GIRK1/X channels, to our knowledge. This discovery represents the first step toward developing potent and selective non-GIRK1/X channel probes. Such molecules will help elucidate the role of GIRK channels in addiction, potentially establishing a foundation for future development of therapies utilizing targeted GIRK channel modulation.

中文翻译：

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VU0529331 的发现和表征，这是一种同聚 G 蛋白门控内向整流钾 (GIRK) 通道的合成小分子激活剂。

G 蛋白门控内向整流钾 (GIRK) 通道是全身细胞兴奋性的重要调节因子。GIRK 通道是 Kir3.1-4 (GIRK1-4) 亚基的异四聚体和同源四聚体组合。不同的亚基组合在整个中枢神经系统 (CNS) 和外周表达，并且大多数这些组合都包含 GIRK1 亚基。例如，中枢神经系统中的 GIRK 通道主要由 GIRK1 和 GIRK2 亚基组成，而心房肌细胞中的 GIRK 通道主要由 GIRK1 和 GIRK4 亚基组成。尽管绝大多数 GIRK 通道包含 GIRK1 亚基，但表达不含 GIRK1 的 GIRK（非 GIRK1/X）通道的离散细胞群体确实存在。例如，大脑腹侧被盖区的多巴胺能神经元与成瘾和奖赏相关，但不表达 GIRK1 亚基。使用亚基选择性药理学探针靶向这些非 GIRK1/X 通道可能会带来关于 GIRK 通道如何参与奖赏和成瘾的重要见解。这些见解反过来可能揭示治疗或预防成瘾的治疗机会。此前，我们实验室发现了可以特异性调节含有GIRK1的GIRK通道活性的小分子。然而，从这些支架生成对非 GIRK1/X 通道有活性的化合物的努力尚未成功。最近，伊维菌素被证明可以调节非 GIRK1/X 通道，并且历史上，伊维菌素已知可以调节多种神经元通道和受体。此外，伊维菌素是一种复杂的天然产物，这使得它成为开发更具选择性、更有效和更有效的化合物的一个具有挑战性的起点。因此，虽然伊维菌素作为非 GIRK1/X 通道激活剂提供了概念验证，但其用途有限。因此，我们试图发现一种合成小分子，作为开发非 GIRK1/X 通道调节剂的起点。为了实现这一目标，我们使用高通量铊通量测定来筛选 100 000 种化合物库，以寻找同聚 GIRK2 通道的激活剂。使用这种方法，我们发现了 VU0529331，据我们所知，这是第一个被报道可激活非 GIRK1/X 通道的合成小分子。这一发现代表了开发有效且选择性的非 GIRK1/X 通道探针的第一步。这些分子将有助于阐明 GIRK 通道在成瘾中的作用，可能为未来开发利用靶向 GIRK 通道调节的疗法奠定基础。