N-terminus urea-substituted chemotactic peptides: New potent agtagonists and antagonists toward the neutrophil fMLF receptor
N-terminus urea-substituted chemotactic peptides: New potent agtagonists and antagonists toward the neutrophil fMLF receptor
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DOI：
10.1021/jm950908d
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发表时间：
1996-03-01
影响因子：
7.3
通讯作者：
Solomon, HF
中科院分区：
文献类型：
--
作者：
Higgins, JD;Bridger, GJ;Solomon, HF
在真核细胞和原核细胞中都观察到细胞沿着化学浓度梯度定向迁移（趋化性）。这一过程在人中性粒细胞中由多种内源性和外源性趋化因子触发。1975年，细菌分离物三肽N-甲酰基-Met-Leu-Phe（fMLF）被鉴定为有效的中性粒细胞化学引诱物，1或更具体地，趋化肽（cp）。已经确定，cps通过特异性质膜受体与中性粒细胞结合，正是这种相互作用启动了趋化性，将细胞导向感染和炎症部位。2受体结合事件还启动嗜酸性粒细胞的“代谢爆发”，包括细胞毒性超氧自由基的产生和蛋白水解酶的释放。这些细胞过程构成了免疫系统抵御原核生物入侵的第一道防线。3 fMLF受体拮抗剂在炎性和感染性疾病领域的诊断和治疗应用中是令人感兴趣的。4几个实验室已经研究了cp激动剂/拮抗剂活性所需的结构特征，并且已经制备和筛选了各种天然和非天然寡肽序列。[5]然而，在所报道的广泛的cps的N-末端的详细阐述方面，所做的工作相对较少。这部分是由于这样的事实，即对于典型的寡肽cps，通常认为N-末端是最大趋化活性所需的，并且显著的N-末端改变导致受体结合降低。5a实际上，与fMLF相比，MLF的N-末端的游离氨基和乙酰化的存在均导致激动剂活性的急剧损失。6 N-氨基甲酰基-MLF（1，图1，表1）也显示出降低的激动剂活性，也有报道。5d然而，将t-Boc基团并入cps的N-末端（即t-Boc-FDLFDLF 7，8）赋予拮抗剂活性，尽管结合效力显著损失。cps的C-末端的改变似乎对结合亲和力的影响不太显著，仅羰基官能团是有效活性所需的。5虽然fMLF受体-配体复合物的确切结构尚未确定，但这些观察结果表明cp的N-末端与fMLF受体相互作用。因此，预期cp上的任何N-末端封闭基团将通过货车德瓦尔相互作用和电子相互作用的组合与受体直接相互作用，这进一步受到每个特定官能团赋予的构象灵活性程度的影响。然而，在目前对fMLF受体结构的了解水平下，很难预测CP在N-末端官能化后如何整体适合受体口袋。在肽的N-末端存在大量可以预见的衍生化。9如前所述，已经报道了氨基甲酸酯衍生的cps（即t-Boc-MLF，一种中等活性的拮抗剂6），我们的实验室最近制备了几种其他代表性的N-氨基甲酸酯，发现其具有中等的激动剂或拮抗剂活性，这取决于氨基甲酸酯的类型。4在本工作中，我们合成了一系列新的N-脲基-MLF和N-脲基-FDLFDLF cps，
The directed migration of cells along a chemical concentration gradient (chemotaxis) is observed in both eukaryotic and prokaryotic cells. This process is triggered in human neutrophils by a variety of endogenous and exogenous chemotactic factors. In 1975, the bacterial isolate tripeptide N-formyl-Met-Leu-Phe (fMLF) was identified as a potent neutrophil chemoattractant, 1 or more specifically, a chemotactic peptide (cp). It is well established that cps bind to neutrophils via specific plasma-membrane receptors and that it is this interaction that initiates chemotaxis, which directs the cells to sites of infection and inflammation. 2 The receptor binding event also initiates the neutrophils’“metabolic burst”, which includes the production of cytotoxic superoxide radicals and the release of proteolytic enzymes. These cellular processes comprise the immune system’s first line of defense against invading prokaryotic organisms. 3 fMLF receptor antagonists are of interest for use in diagnostic and therapeutic applications in the areas of inflammatory and infectious diseases. 4 Several laboratories have investigated the structural features required for cp agonist/antagonist activity, and a variety of natural and unnatural oligopeptide sequences have been prepared and screened. 5 Relatively little work has been done, however, on elaboration of the N-terminus of the wide range of cps reported. This is due in part to the fact that with typical oligopeptide cps N-formylation is generally thought to be required for maximum chemotactic activity, and significant N-terminus alterations result in decreased receptor binding. 5a Indeed, the presence of a free amino group and acetylation at the N-terminus of MLF both result in drastic losses in agonist activity as compared to fMLF. 6 N-Carbamoyl-MLF (1, Figure 1, Table 1), which also displayed decreased agonist activity, has been reported as well. 5d Incorporation of a t-Boc group onto the N-termini of cps (ie, t-Boc-FDLFDLF7, 8), however, imparts antagonist activity, albeit with a significant loss in binding potency. Alterations at the C-termini of cps appear to have less significant effects on binding affinity, with only the carbonyl functional group being required for potent activity. 5 Although the exact structure of an fMLF receptor-ligand complex has not yet been characterized, observations such as these suggest that the N-terminus of a cp interacts with the fMLF receptor. It then follows that any N-terminal blocking group on a cp would be expected to interact directly with the receptor via a combination of van der Waal and electronic interactions, which are further influenced by the degree of conformational flexibility imparted by each particular functional group. At the current level of knowledge on the structure of the fMLF receptor, however, it is difficult to predict how a cp’s overall fit into the receptor pocket will be effected upon N-terminal functionalization. There are large number of derivatizations at the N-terminus of a peptide that one can envision. 9 As mentioned earlier, carbamate-derivatized cps have been reported (ie, t-Boc-MLF, a modestly active antagonist6) and several other representative N-carbamates have been prepared recently in our labs which were found to possess modest agonist or antagonist activity depending on the type of carbamate. 4 During the course of this work, we synthesized a series of new N-ureido-MLF and N-ureido-FDLFDLF cps which displayed unexpectedly