ConoPeptides - G-Protein Coupled Receptors

该项目的长期目标是表征靶向G蛋白偶联受体（GPCR）的芋螺肽的结构，生物化学和药理学特性。在本研究中，我们将重点研究一种独特的镇痛肽Contulakin-G的构效关系， 神经降压素受体（NTRs）。Contulakin-G是从地纹芋螺（Conus geographus）毒液中分离得到的16个氨基酸残基的多肽。这种肽与内源性神经肽神经降压素（NT）的C-末端序列相似，但它也包含一个不寻常的翻译后修饰：Thr残基的O-糖基化。Contulakin-G的独特药理学性质是这种非常有效的镇痛化合物是神经降压素受体的低亲和力、非脱敏激动剂。与Contulakin-G形成鲜明对比的是，NT作为镇痛剂的效力低600倍，但它是一种高亲和力激动剂，容易使NTR脱敏。结果与 非糖基化的Contulakin-G表明，Contulakin-G和神经降压素之间的这种深刻的机制差异可以通过糖基化和不同的N-末端序列两者的存在来解释。我们建议系统地探索Contulakin-G和 神经降压素决定了芋螺肽独特药理学特性。该提案的具体目标包括：（1）化学合成Contulakin-G和神经降压素类似物，其肽和糖基结构不同，（2）Contulakin-G类似物体外药理学性质的表征，（3） 评价合成的类似物的镇痛性质及其镇痛机制;（4）发现与Contulakin-G属于同一基因家族的新成员。该研究的结果将允许更好地定义Contulakin-G独特镇痛特性的结构决定因素，以及测试这种糖肽产生的强效镇痛作用的假设， 至少部分是由于其不使神经降压素受体脱敏的能力。这一提议的长期结果可能导致开发针对GPCR的新型化合物。

The long-term goal of this project is to characterize structural, biochemical and pharmacological properties of conopeptides that target G-protein coupled receptors (GPCRs). In the proposed research, we will focus on studying structure-activity-relationships of a unique analgesic conopeptide, Contulakin-G, targeting neurotensin receptors (NTRs). Contulakin-G is a 16-residue peptide isolated from venom of Conus geographus. This peptide shares the C-terminal sequence similarity with an endogenous neuropeptide, neurotensin (NT), but it also contains an unusual posttranslational modification: O-glycosylation of a Thr residue. A unique pharmacological property of Contulakin-G is that this very potent analgesic compound is a low-affinity, non-desensetizing agonist for neurotensin receptors. In stark contrast to Contulakin-G, NT is 600-fold less potent as analgesic, but it is a high-affinity agonist that easily desensitizes NTRs. Results with non-glycosylated Contulakin-G suggested that such profound mechanistic differences between Contulakin-G and neurotensin can be accounted for by the presence of both, glycosylation and distinct N-terminal sequences. We propose to systematically explore structural differences between Contulakin-G and neurotensin that determine a unique pharmacological profile of this conopeptide. Specific aims of this proposal include: (1) chemical synthesis of Contulakin-G and neurotensin analogs varying in the peptidic and glycosyl structures, (2) characterization of in vitro pharmacological properties of Contulakin-G analogs, (3) assessment of analgesic properties of the synthesized ananlogs and their mechanism of analgesia, (4) discovery of novel members of the same gene family that Contulakin-G belongs to. Results from the research will allow to better define structural determinants of unique analgesic properties of Contulakin-G, as well as to test a hypothesis that the potent analgesia produced by this glycopeptide can, at least in part, be accounted for by its ability to not desensitize neurotensin receptor. The long-term outcomes of this proposal may lead to development of novel compounds targeting GPCRs.