The histamine H₁ receptor (H₁R) has recently been implicated in mediating cell proliferation and cancer progression; therefore, high-affinity H₁R-selective fluorescent ligands are desirable tools for further investigation of this behavior in vitro and in vivo. We previously reported a H₁R fluorescent ligand, bearing a peptide-linker, based on antagonist VUF13816 and sought to further explore structure–activity relationships (SARs) around the linker, orthostere, and fluorescent moieties. Here, we report a series of high-affinity H₁R fluorescent ligands varying in peptide linker composition, orthosteric targeting moiety, and fluorophore. Incorporation of a boron-dipyrromethene (BODIPY) 630/650-based fluorophore conferred high binding affinity to our H₁R fluorescent ligands, remarkably overriding the linker SAR observed in corresponding unlabeled congeners. Compound 31a, both potent and subtype-selective, enabled H₁R visualization using confocal microscopy at a concentration of 10 nM. Molecular docking of 31a with the human H₁R predicts that the optimized peptide linker makes interactions with key residues in the receptor.

中文翻译：

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组胺 H1 受体基于肽接头的荧光配体的优化

组胺 H ₁受体 (H ₁ R) 最近与介导细胞增殖和癌症进展有关；因此，高亲和力 H ₁ R 选择性荧光配体是进一步研究这种体外和体内行为的理想工具。我们之前报道了一种基于拮抗剂 VUF13816 的带有肽接头的H _{1 R 荧光配体，并试图进一步探索接头、正构和荧光部分周围的构效关系 (SAR)。}在这里，我们报告了一系列高亲和力 H ₁R 荧光配体的肽接头组成、正构靶向部分和荧光团各不相同。掺入基于硼-二吡咯甲烯 (BODIPY) 630/650 的荧光团赋予我们的 H ₁ R 荧光配体高结合亲和力，显着压倒了在相应未标记同类物中观察到的接头 SAR。化合物31a既有效又具有亚型选择性，可在 10 nM 的浓度下使用共聚焦显微镜实现 H _{1 R 可视化。}31a与人类 H ₁ R的分子对接预测优化的肽接头与受体中的关键残基相互作用。