Weng Chi-Chang, Riad Aladdin, Lieberman Brian P, Xu Kuiying, Peng Xin, Mikitsh John L, Mach Robert H
HARC and Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan 333, Taiwan.
Department of Nuclear Medicine and Center for Advanced Molecular Imaging and Translation, Linkou Chang Gung Memorial Hospital, Taoyuan 333, Taiwan.
Pharmaceuticals (Basel). 2022 Dec 15;15(12):1564. doi: 10.3390/ph15121564.
The sigma-2 receptor/transmembrane protein 97 (σ2R/TMRM97) is a promising biomarker of tumor proliferation and a target for cancer therapy. [H]DTG has been used to evaluate σ2R/TMEM97 binding affinity in compound development studies. However, [H]DTG has equal and moderate binding affinities to both sigma 1 receptor (σ1R) and σ2R/TMEM97. Furthermore, co-administration with the σ1R masking compound (+)-pentazocine may cause bias in σ2R/TMEM97 binding affinity screening experiments. We have developed a radioiodinated ligand, [I]RHM-4, which has high affinity and selectivity for σ2R/TMEM97 versus σ1R. In this study, a head-to-head comparison between [H]DTG and [I]RHM-4 on the binding affinity and their effectiveness in σ2R/TMEM97 compound screening studies was performed. The goal of these studies was to determine if this radioiodinated ligand is a suitable replacement for [H]DTG for screening new σ2R/TMEM97 compounds. Furthermore, to delineate the binding properties of [I]RHM-4 to the σ2R/TMEM97, the structure of RHM-4 was split into two fragments. This resulted in the identification of two binding regions in the σ2R, the "DTG" binding site, which is responsible for binding to the σ2R/TMEM97, and the secondary binding site, which is responsible for high affinity and selectivity for the σ2R/TMEM97 versus the σ1R. The results of this study indicate that [I]RHM-4 is an improved radioligand for in vitro binding studies of the σ2R/TMEM97 versus [H]DTG.
σ2受体/跨膜蛋白97（σ2R/TMRM97）是一种很有前景的肿瘤增殖生物标志物和癌症治疗靶点。在化合物开发研究中，[H]DTG已被用于评估σ2R/TMEM97的结合亲和力。然而，[H]DTG对σ1受体（σ1R）和σ2R/TMEM97具有相同的中等结合亲和力。此外，与σ1R掩蔽化合物（+）-喷他佐辛共同给药可能会在σ2R/TMEM97结合亲和力筛选实验中导致偏差。我们开发了一种放射性碘化配体[I]RHM-4，它对σ2R/TMEM97相对于σ1R具有高亲和力和选择性。在本研究中，对[H]DTG和[I]RHM-4在结合亲和力及其在σ2R/TMEM97化合物筛选研究中的有效性进行了直接比较。这些研究的目的是确定这种放射性碘化配体是否是[H]DTG筛选新的σ2R/TMEM97化合物的合适替代品。此外，为了描述[I]RHM-4与σ2R/TMEM97的结合特性，将RHM-4的结构拆分为两个片段。这导致在σ2R中鉴定出两个结合区域，即负责与σ2R/TMEM97结合的“DTG”结合位点，以及负责σ2R/TMEM97相对于σ1R的高亲和力和选择性的二级结合位点。本研究结果表明，与[H]DTG相比，[I]RHM-4是用于σ2R/TMEM97体外结合研究的改进型放射性配体。
