4-Alkyloxyimino-cytosine nucleotides: tethering approaches to molecular probes for the P2Y6 receptor
作者:P. Suresh Jayasekara、Matthew O. Barrett、Christopher B. Ball、Kyle A. Brown、Eszter Kozma、Stefano Costanzi、Lucia Squarcialupi、Ramachandran Balasubramanian、Hiroshi Maruoka、Kenneth A. Jacobson
DOI:10.1039/c3md00132f
日期:——
4-Alkyloxyimino derivatives of pyrimidine nucleotides display high potency as agonists of certain G protein-coupled P2Y receptors (P2YRs). In an effort to functionalize a P2Y6R agonist for fluorescent labeling, we probed two positions (N4 and γ-phosphate of cytidine derivatives) with various functional groups, including alkynes for click chemistry. Functionalization of extended imino substituents at the 4 position of the pyrimidine nucleobase of CDP preserved P2Y6R potency generally better than γ-phosphoester formation in CTP derivatives. Fluorescent Alexa Fluor 488 conjugate 16 activated the human P2Y6R expressed in 1321N1 human astrocytoma cells with an EC50 of 9 nM, and exhibited high selectivity for this receptor over other uridine nucleotide-activated P2Y receptors. Flow cytometry detected specific labeling with 16 to P2Y6R-expressing but not to wild-type 1321N1 cells. Additionally, confocal microscopy indicated both internalized 16 (t1/2 of 18 min) and surface-bound fluorescence. Known P2Y6R ligands inhibited labeling. Theoretical docking of 16 to a homology model of the P2Y6R predicted electrostatic interactions between the fluorophore and extracellular portion of TM3. Thus, we have identified the N4-benzyloxy group as a structurally permissive site for synthesis of functionalized congeners leading to high affinity molecular probes for studying the P2Y6R.
4-烷氧亚氨基嘧啶核苷酸衍生物作为某些G蛋白偶联P2Y受体(P2YRs)的激动剂显示出高度效力。为了对P2Y6R激动剂进行荧光标记,我们在两个位置(胞苷衍生物的N4位和γ-磷酸基团)上探查了包括炔烃在内的各种功能团,用于点击化学反应。在CDP的嘧啶核碱4位上进行扩展亚氨基取代,相比于CTP衍生物中的γ-磷酸酯形成,通常更好地保持了P2Y6R的效力。荧光染料Alexa Fluor 488的共轭物16激活了在1321N1人星形胶质瘤细胞中表达的人P2Y6R,其EC50为9 nM,并且对这种受体的选择性远高于其他由尿嘧啶核苷酸激活的P2Y受体。流式细胞术检测到16对表达P2Y6R的细胞有特异性标记,而对野生型1321N1细胞无标记。此外,共聚焦显微镜显示16被内化(半衰期18分钟)并有表面结合的荧光。已知的P2Y6R配体抑制标记。16与P2Y6R的同源模型的理论对接预测了荧光团与TM3的外部部分之间的静电相互作用。因此,我们确定了N4-苄氧基团作为合成功能化类似物的结构容许位点,从而得到用于研究P2Y6R的高亲和力分子探针。