Pharmaceuticals Research Laboratories, Sanwa Kagaku Kenkyusho Co., Ltd., Mie, Japan.
Pharmaceuticals Research Laboratories, Sanwa Kagaku Kenkyusho Co., Ltd., Mie, Japan
Mol Pharmacol. 2022 Oct;102(4):183-195. doi: 10.1124/molpharm.122.000522. Epub 2022 Aug 5.
The human calcium-sensing receptor (CaSR) is a G protein-coupled receptor that maintains extracellular Ca homeostasis by regulating the secretion of parathyroid hormone. Upacicalcet is a novel positive allosteric modulator of CaSR that is used for the treatment of secondary hyperparathyroidism. In the present study, to clarify the binding site of upacicalcet to CaSR, we conducted binding studies and agonistic activity studies in HEK-293T cells expressing human CaSR (intact and mutant) and an docking-simulation analysis. As a result, upacicalcet competed with L-tryptophan and was thought to affect the amino acid binding site. In addition, the effects of substitutions at the amino acid binding site on the binding abilities to upacicalcet as well as the effects on receptor function as measured using inositol-1 monophosphate accumulation were examined. Upacicalcet interacted with several CaSR residues that constitute the amino acid binding site. Based on these results, we performed an analysis and obtained a binding mode, consistent with the study results. Our study revealed that upacicalcet is a novel secondary hyperparathyroidism drug that targets the amino acid binding site of CaSR. Upacicalcet is expected to become a new treatment option for secondary hyperparathyroidism because the binding site differs from that of conventional drugs; consequently, it may be effective for patients who are not sensitive to conventional drugs, and it may have a superior safety profile. SIGNIFICANCE STATEMENT: Upacicalcet interacts with several residues that constitute the amino acid binding site of the calcium-sensing receptor (CaSR) and shows a potent positive allosteric activity. This mechanism differs from those of conventional drugs. Therefore, upacicalcet can be regarded as a novel secondary hyperparathyroidism drug that acts on the amino acid binding site of CaSR.
人钙敏感受体（CaSR）是一种 G 蛋白偶联受体，通过调节甲状旁腺激素的分泌来维持细胞外钙的稳态。Upacicalcet 是一种新型的 CaSR 正变构调节剂，用于治疗继发性甲状旁腺功能亢进症。在本研究中，为了阐明 Upacicalcet 与 CaSR 的结合位点，我们在表达人 CaSR（完整和突变体）的 HEK-293T 细胞中进行了结合研究和激动活性研究，并进行了对接模拟分析。结果表明，Upacicalcet 与 L-色氨酸竞争，可能影响氨基酸结合位点。此外，还研究了氨基酸结合位点的取代对 Upacicalcet 结合能力以及对受体功能（通过肌醇-1 单磷酸积累测定）的影响。Upacicalcet 与构成氨基酸结合位点的几个 CaSR 残基相互作用。基于这些结果，我们进行了分子对接分析，并获得了与实验结果一致的结合模式。我们的研究表明，Upacicalcet 是一种新型的治疗继发性甲状旁腺功能亢进症的药物，其作用靶点是 CaSR 的氨基酸结合位点。由于结合位点与传统药物不同，因此 Upacicalcet 有望成为治疗继发性甲状旁腺功能亢进症的新选择；它可能对不敏感于传统药物的患者有效，并且可能具有更好的安全性。意义陈述：Upacicalcet 与构成钙敏感受体（CaSR）氨基酸结合位点的几个残基相互作用，并表现出强大的正变构活性。这种机制与传统药物不同。因此，Upacicalcet 可被视为一种新型的作用于 CaSR 氨基酸结合位点的治疗继发性甲状旁腺功能亢进症的药物。
