Department of Physiology, Bio5 Collaborative Research Institute, Arizona Respiratory Center, Arizona Health Sciences Center, Tucson, Arizona 85724, USA.
J Biol Chem. 2011 May 27;286(21):19076-88. doi: 10.1074/jbc.M110.185264. Epub 2011 Apr 5.
Protease-activated receptor-2 (PAR(2)) is one of four protease-activated G-protein-coupled receptors. PAR(2) is expressed on multiple cell types where it contributes to cellular responses to endogenous and exogenous proteases. Proteolytic cleavage of PAR(2) reveals a tethered ligand that activates PAR(2) and two major downstream signaling pathways: mitogen-activated protein kinase (MAPK) and intracellular Ca(2+) signaling. Peptides or peptidomimetics can mimic binding of the tethered ligand to stimulate signaling without the nonspecific effects of proteases. The most commonly used peptide activators of PAR(2) (e.g. SLIGRL-NH(2) and SLIGKV-NH(2)) lack potency at the receptor. However, although the potency of 2-furoyl-LIGRLO-NH(2) (2-f-LIGRLO-NH(2)) underscores the use of peptidomimetic PAR(2) ligands as a mechanism to enhance pharmacological action at PAR(2), 2-f-LIGRLO-NH(2) has not been thoroughly evaluated. We evaluated the known agonist 2-f-LIGRLO-NH(2) and two recently described pentapeptidomimetic PAR(2)-specific agonists, 2-aminothiazol-4-yl-LIGRL-NH(2) (2-at-LIGRL-NH(2)) and 6-aminonicotinyl-LIGRL-NH(2) (6-an-LIGRL-NH(2)). All peptidomimetic agonists stimulated PAR(2)-dependent in vitro physiological responses, MAPK signaling, and Ca(2+) signaling with an overall rank order of potency of 2-f-LIGRLO-NH(2) ≈ 2-at-LIGRL-NH(2) > 6-an-LIGRL-NH(2) ≫ SLIGRL-NH(2). Because PAR(2) plays a major role in pathological pain conditions and to test potency of the peptidomimetic agonists in vivo, we evaluated these agonists in models relevant to nociception. All three agonists activated Ca(2+) signaling in nociceptors in vitro, and both 2-at-LIGRL-NH(2) and 2-f-LIGRLO-NH(2) stimulated PAR(2)-dependent thermal hyperalgesia in vivo. We have characterized three high potency ligands that can be used to explore the physiological role of PAR(2) in a variety of systems and pathologies.
蛋白酶激活受体 2（PAR(2)）是四种蛋白酶激活的 G 蛋白偶联受体之一。PAR(2) 表达于多种细胞类型，在细胞对内源性和外源性蛋白酶的反应中发挥作用。PAR(2) 的蛋白水解切割揭示了一个连接的配体，该配体激活 PAR(2) 和两个主要的下游信号通路：丝裂原活化蛋白激酶（MAPK）和细胞内 Ca(2+)信号。肽或肽类似物可以模拟连接配体的结合，从而刺激信号转导，而不会产生蛋白酶的非特异性影响。最常用的 PAR(2) 肽激活剂（例如 SLIGRL-NH(2)和 SLIGKV-NH(2)）在受体上缺乏效力。然而，尽管 2-糠酰基-LIGRLO-NH(2)（2-f-LIGRLO-NH(2)）的效力突出了使用肽拟似物 PAR(2)配体作为增强 PAR(2)药理学作用的机制，但 2-f-LIGRLO-NH(2)尚未得到彻底评估。我们评估了已知的激动剂 2-f-LIGRLO-NH(2)和最近描述的两种五肽肽拟似物 PAR(2)特异性激动剂，2-氨基噻唑-4-基-LIGRL-NH(2)（2-at-LIGRL-NH(2)）和 6-氨基烟酰基-LIGRL-NH(2)（6-an-LIGRL-NH(2)）。所有肽拟似物激动剂均刺激 PAR(2)依赖性体外生理反应、MAPK 信号转导和 Ca(2+)信号转导，效力总体顺序为 2-f-LIGRLO-NH(2)≈2-at-LIGRL-NH(2)>6-an-LIGRL-NH(2)>SLIGRL-NH(2)。由于 PAR(2) 在病理性疼痛状态中起主要作用，并测试肽拟似物激动剂在体内的效力，我们在与伤害感受相关的模型中评估了这些激动剂。所有三种激动剂均在体外激活伤害感受器中的 Ca(2+)信号转导，并且 2-at-LIGRL-NH(2)和 2-f-LIGRLO-NH(2)均在体内刺激 PAR(2)依赖性热痛觉过敏。我们已经描述了三种高效力配体，可用于探索 PAR(2)在各种系统和病理中的生理作用。
