环腺苷二磷酸核糖（cADPR）是一内源的钙离子激动的核苷酸并调节许多重要生理功能。我们用一个全新的光亲和标记的cADPR激动剂找到甘油醛-3-磷酸脱氢酶(GAPDH)就是长久以来研究者所找寻的cADPR结合蛋白，并证明GAPDH对于cADPR所诱导的通过兰诺定受体(RyRs)产生的钙激动活性是必需的。基于模拟的cADPR-GAPDH复合物结构，我们还进行了药物筛选，确定了一些与GAPDH上的cADPR结合位点具有较高结合力的小分子，并发现其中一个化合物C244是一个潜在的cADPR拮抗剂。我们将进一步研究cADPR结合GAPDH通过RyRs所引发钙离子从内质网释放的分子机制，并合成和表征这些全新cADPR激动剂或拮抗剂的药理活性。鉴于cADPR介导的钙信号通路在细胞生理活动中的重要作用，研究该信号通路的分子机制并发现全新的cADPR激动剂或拮抗剂对于治疗cADPR相关的疾病具有重要的意义。

The Ca2+-signaling pathway mediated by cyclic adenosine diphosphoribose (cADPR) is ubiquitous and the functions it regulates are equally diverse. Understanding the molecular mechanisms involved in this novel signaling pathway is not only scientifically important but also clinically relevant. The latter has clearly been demonstrated in CD38 knockout mice. CD38 is the dominant enzyme for synthesizing cADPR in mammalian systems and CD38 knockout mice exhibited multiple physiological defects, ranging from impaired immune responses, metabolic disturbances, to social behavioral modifications. Many extracellular stimuli have been shown to induce cADPR production that leads to calcium release or influx, establishing cADPR as a second messenger. Ample evidence indicates that cADPR targets ryanodine receptors (RyRs) on ER in many cell types, yet cADPR does not directly act on the receptor. We hypothesize that a bridging protein is required for the ability of cADPR to induce Ca2+ release via RyRs. We, therefore, synthesized a novel photoaffinity labeling cADPR agonist, PAL-cIDPRE, and subsequently applied it to purify its binding proteins in human Jurkat T cells. We identified glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as one of cADPR binding protein(s), characterized the binding affinity between cADPR and GAPDH in vitro by SPR assay, and mapped the cADPR’s binding sites in GAPDH. We further demonstrated that cADPR induced the transient interaction between GAPDH and RyRs in vivo, and GAPDH knockdown abolished cADPR-induced Ca2+ release. On the other hand, GAPDH did not catalyze cADPR into any other known or novel compound(s). Our data suggest that GADPH is the long-sought-after cADPR binding protein and is required for cADPR-mediated Ca2+ mobilization from ER via RyRs. Based on the simulated cADPR-GAPDH complex structure, we also performed the structure-based drug screening, identified a number of small chemicals with high docking scores to cADPR’s binding pocket in GAPDH, and found one of these compounds, C244, is a potential cADPR antagonist. Here we propose to (1) mechanistically study how cADPR binds with GAPDH to trigger Ca2+ release from ER via RyRs, and (2) chemically synthesize and pharmacologically characterize novel cADPR agonist(s) or antagonist(s). Given the pivotal role of cADPR-mediated Ca2+ signaling pathway in a wide variety of cellular processes, understanding the molecular mechanisms of this signaling pathways and identifying novel cADPR agonist(s) or antagonist(s) will be fundamentally important for pharmaceutical intervention in treatment of cADPR-related human disorders.