Li J, Matsuura J E, Waugh D J, Adrian T E, Abel P W, Manning M C, Smith D D
Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178, USA.
J Med Chem. 1997 Sep 12;40(19):3071-6. doi: 10.1021/jm9608164.
A structure-activity study was performed to examine the role of position 14 of human alpha-calcitonin gene-related peptide (h-alpha-CGRP) in activating the CGRP receptor. Interestingly, position 14 of h-alpha-CGRP contains a glycyl residue and is part of an alpha-helix spanning residues 8-18. Analogues [Ala14]-h-alpha-CGRP, [Aib14]-h-alpha-CGRP, [Asp14]-h-alpha-CGRP, [Asn14]-h-alpha-CGRP, and [Pro14]-h-alpha-CGRP were synthesized by solid phase peptide methodology and purified by RP-HPLC. Secondary structure was measured by circular dichroism spectroscopy. Agonist activities were determined as the analogues' ability to stimulate amylase secretion from guinea pig pancreatic acini and to relax precontracted porcine coronary arteries. Analogues [Ala14]-h-alpha-CGRP, [Aib14]-h-alpha-CGRP, [Asp14]-h-alpha-CGRP, and [Asn14]-h-alpha-CGRP, all containing residues with a high helical propensity in position 14, were potent full agonists compared to h-alpha-CGRP in both tissues. Interestingly, replacement of Gly14 of h-alpha-CGRP with these residues did not substantially increase the helical content of these analogues. [Pro14]-h-alpha-CGRP, predictably, has significantly lower helical content and is a 20-fold less potent agonist on coronary artery, known to contain CGRP-1 receptor subtypes, and an antagonist on pancreatic acini, known to contain CGRP-2 receptor subtypes. In conclusion, the residue in position 14 plays a structural role in stabilizing the alpha-helix spanning residues 8-18. The alpha-helix is crucial for maintaining highly potent agonist effects of h-alpha-CGRP at CGRP receptors. The wide variety of functional groups that can be tolerated in position 14 with no substantial modification of agonist effects suggests the residue in this position is not in contact with the CGRP receptor. [Pro14]-h-alpha-CGRP may be a useful pharmacological tool to distinguish between CGRP-1 and CGRP-2 receptor subtypes.
进行了一项结构-活性研究，以考察人α-降钙素基因相关肽（h-α-CGRP）第14位在激活CGRP受体中的作用。有趣的是，h-α-CGRP的第14位含有一个甘氨酰残基，并且是跨越第8 - 18位残基的α-螺旋的一部分。通过固相肽法合成了类似物[Ala14]-h-α-CGRP、[Aib14]-h-α-CGRP、[Asp14]-h-α-CGRP、[Asn14]-h-α-CGRP和[Pro14]-h-α-CGRP，并通过反相高效液相色谱法进行纯化。通过圆二色光谱法测定二级结构。激动剂活性通过类似物刺激豚鼠胰腺腺泡分泌淀粉酶以及舒张预先收缩的猪冠状动脉的能力来确定。与h-α-CGRP相比，在两个组织中，所有在第14位含有具有高螺旋倾向残基的类似物[Ala14]-h-α-CGRP、[Aib14]-h-α-CGRP、[Asp14]-h-α-CGRP和[Asn14]-h-α-CGRP都是有效的完全激动剂。有趣的是，用这些残基取代h-α-CGRP的Gly14并没有显著增加这些类似物的螺旋含量。可以预见，[Pro14]-h-α-CGRP的螺旋含量显著较低，在已知含有CGRP - 1受体亚型的冠状动脉上其激动剂效力低20倍，而在已知含有CGRP - 2受体亚型的胰腺腺泡上则是拮抗剂。总之，第14位的残基在稳定跨越第8 - 18位残基的α-螺旋中起结构作用。α-螺旋对于维持h-α-CGRP在CGRP受体上的高效激动剂作用至关重要。第14位能够耐受多种官能团且激动剂作用无实质性改变，这表明该位置的残基不与CGRP受体接触。[Pro14]-h-α-CGRP可能是区分CGRP - 1和CGRP - 2受体亚型的有用药理学工具。
