Neurotensin binding to extraneural and neural receptors: comparison with biological activity and structure--activity relationships.
Neurotensin binding to extraneural and neural receptors: comparison with biological activity and structure--activity relationships.
复制标题
神经降压素与神经外和神经受体的结合：生物活性和结构-活性关系的比较。
作者：
P. Kitabgi;C. Poustis;C. Granier;J. van Rietschoten;J. Rivier;J. Morgat;P. Freychet
[~ 3 H]神经降压素与人结肠癌细胞系HT-29的结合特性与[~ 3 H]神经降压素与大鼠脑突触膜的结合特性进行了比较。这两个系统被用来作为放射性受体测定神经降压素和18神经降压素合成类似物，从而得到的结合亲和力进行了比较，从肽的能力，以合同分离的豚鼠回肠纵向平滑肌条的生物效力。氚标记的神经降压素与HT 29细胞特异性可逆结合。[3 H]神经降压素在24°C下与细胞结合的特征是涉及一类非合作结合位点的简单双分子反应。从缔合动力学和平衡实验中独立获得的Kd值为1.5 nM;总结合能力为37 fmol/106个细胞（22，000个神经降压素结合位点/细胞）。结构上与神经降压素无关的肽不影响[3 H]神经降压素结合。这些结合特性是非常相似的观察到的结合[3 H]神经降压素大鼠脑突触膜。当神经降压素和神经降压素类似物的结合亲和力在神经（HT 29细胞）和神经（脑膜）系统中进行比较时，观察到两种结合系统之间高度显著的相关性。当神经降压素和神经降压素类似物的生物学效价与它们在神经或神经胶质放射受体测定中的结合亲和力进行比较时，也发现了高度显著的相关性。精氨酸残基8和9上的正电荷以及精氨酸9的L-构型对于结合和生物活性是重要的。在神经降压素分子的11位需要L-构型的芳族残基。Ile 12和羧基末端残基Leu 13的侧链甲基以及Leu 13以L-构型存在是活性所需的。
The binding of [3H]neurotensin to a cell line (HT 29) derived from a human colon carcinoma was characterized and compared with [3H]neurotensin binding to rat brain synaptic membranes. Both systems were used as radioreceptor assays for neurotensin and 18 neurotensin synthetic analogs, and the binding affinities thus derived were compared to the biological potencies obtained from the peptide abilities to contract isolated longitudinal smooth muscle strips of the guinea pig ileum. Tritiated neurotensin bound specifically and reversibly to HT 29 cells. The characteristics of [3H]neurotensin binding to cells at 24°C were those of a simple, bimolecular reaction involving one class of noncooperative binding sites. A Kd value of 1.5 nM was independently obtained from association kinetic and equilibrium experiments; total binding capacity was 37 fmol/106 cells (22,000 neurotensin-binding sites/cell). Peptides structurally not related to neurotensin did not affect [3H]neurotensin binding. These binding characteristics were very similar to those observed for the binding of [3H]neurotensin to rat brain synaptic membranes. When the binding affinities of neurotensin and neurotensin analogs were compared in the extraneural (HT 29 cells) and neural (brain membranes) systems, a highly significant correlation between the two binding systems was observed. A highly significant correlation was also found when the biological potencies of neurotensin and neurotensin analogs were compared with their binding affinities in either the neural or the extraneural radioreceptor assay. The positive charge on both arginyl residues 8 and 9 and the L-configuration of Arg9 were important for binding and biological activity. An aromatic residue in the L-configuration was required in position 11 of the neurotensin molecule. The side-chain methyl groups of Ile12 and carboxy-terminal residue Leu13, as well as the presence of Leu13 in the L-configuration, were required for activity.