Receptor signaling and endocytosis are differentially regulated by somatostatin analogs
Receptor signaling and endocytosis are differentially regulated by somatostatin analogs
复制标题
DOI：
10.1124/mol.105.011767
复制
发表时间：
2005-07-01
影响因子：
3.6
通讯作者：
Schonbrunn, A
中科院分区：
文献类型：
--
作者：
Liu, QS;Cescato, R;Schonbrunn, A
在激素刺激下，sst 2生长抑素受体通过G（i/o）蛋白偶联腺苷酸环化酶，并通过网格蛋白包被的小凹进行快速内吞。在这项研究中，我们确定了配体诱导sst 2受体内化和抑制腺苷酸环化酶的能力之间的关系。免疫细胞化学研究表明，肽激动剂[如生长抑素-14，皮质抑素-17，奥曲肽，伐普肽，KE 108（Tyr 0-环[D-二氨基丁酸-Arg-Phe-Phe- D-Trp-Lys-Thr-Phe]）和SOM 230（环[二氨基乙基氨基甲酰基-羟脯氨酸-苯甘氨酸-D-Trp-Lys-（4-O-苄基）L-Tyr-Phe]）]和非肽激动剂（如L-779，976），刺激人胚肾293和CHO-K1细胞中sst 2受体的快速内吞作用。相反，两种拮抗剂本身不诱导受体内吞作用，并完全阻断激动剂刺激。使用定量酶联免疫吸附测定来测量sst 2受体螯合，我们发现肽激动剂的效力变化超过100倍，但表现出与生长抑素相同的功效14。相反，L-779，976没有诱导最大的受体内化。有趣的是，尽管在用生长抑素14或L-779，976刺激后β抑制蛋白-2被募集到细胞表面sst 2受体，但β抑制蛋白-受体复合物在胞吞途径中较早地与非肽配体解离。尽管所有激动剂（包括L-779，976）对环AMP的最大抑制作用相同，但抑制环AMP和刺激受体内吞作用的效力比相差15倍。在一般情况下，天然肽表现出类似的效力环AMP抑制和受体内吞作用，而短的治疗类似物基本上更有效地抑制环AMP合成。这些结果表明生长抑素类似物调节受体内吞作用和信号传导的活性并不紧密相关，并为诱导SST 2受体的激动剂特异性状态提供了令人信服的证据。
Upon hormone stimulation, the sst2 somatostatin receptor couples to adenylyl cyclase through G(i/o) proteins and undergoes rapid endocytosis via clathrin-coated pits. In this study, we determined the relationship between the ability of ligands to induce sst2 receptor internalization and inhibit adenylyl cyclase. Immunocytochemical studies demonstrated that peptide agonists [ such as somatostatin-14, cortistatin-17, octreotide, vapreotide, KE108 (Tyr0-cyclo[D-diaminobutyric acid-Arg-Phe-Phe- D-Trp-Lys-Thr-Phe]), and SOM230 ( cyclo[ diaminoethylcarbamoyl-hydroxyproline- phenylglycine-D-Trp-Lys-(4-O-benzyl)L- Tyr-Phe])] and nonpeptide agonists ( such as L- 779,976), stimulated the rapid endocytosis of sst2 receptors in human embryonic kidney 293 and CHO-K1 cells. In contrast, two antagonists did not induce receptor endocytosis by themselves and completely blocked agonist stimulation. Using a quantitative enzyme-linked immunosorbent assay to measure sst2 receptor sequestration, we found that peptide agonists varied by more than 100-fold in their potencies but exhibited the same efficacy as somatostatin14. In contrast, L-779,976 did not induce maximal receptor internalization. It is interesting that although beta arrestin-2 was recruited to cell surface sst2 receptors after stimulation with either somatostatin14 or L-779,976, the beta arrestin-receptor complex dissociated earlier in the endocytic pathway with the nonpeptide ligand. Although all agonists, including L-779,976, produced the same maximal inhibition of cyclic AMP, the potency ratio for inhibition of cyclic AMP and stimulation of receptor endocytosis varied by 15-fold. In general, native peptides showed similar potencies for cyclic AMP inhibition and receptor endocytosis, whereas short therapeutic analogs were substantially more potent at inhibiting cyclic AMP synthesis. These results demonstrate that the activity of somatostatin analogs to regulate receptor endocytosis and signaling are not tightly linked and provide compelling evidence for the induction of agonist specific states of the sst2 receptor.