Thermos K, He H T, Wang H L, Margolis N, Reisine T
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104.
Neuroscience. 1989;31(1):131-41. doi: 10.1016/0306-4522(89)90035-3.
The physical properties of brain and pituitary somatostatin receptors were characterized using photocrosslinking techniques. Somatostatin receptors in rat corpus striatum and anterior pituitary membranes were covalently bound to the non-reducible somatostatin analog, [125I]CGP 23996, using the crosslinking agent n-hydroxysuccinimidyl-4-azidobenzoate and ultraviolet light. In striatal membranes, a protein of 60,000 mol. wt was labeled by [125I]CGP 23996. The binding was potently inhibited by somatostatin analogs but not by other biologically active peptides. The labeling of the 60,000 mol. wt protein by [125I]CGP 23996 was diminished by guanine triphosphate gamma thiol, which is consistent with the labeling of a somatostatin receptor coupled to guanine triphosphate binding proteins. The migration of the [125I]CGP 23996 labeled 60,000 mol. wt protein in native sodium dodecyl sulfate-gels was not affected by the reducing agent dithiothreitol, indicating that there is a general lack of disulfide bridges in the striatal somatostatin receptor. The striatal somatostatin receptor was solubilized with the detergent 3-[(3-cholamidopropyl)-dimethylaminoio]-1-propanesulfonate and specifically bound to the lectin wheat germ agglutinin, suggesting that the striatal somatostatin receptor is a glycoprotein. [125I]CGP 23996 also labeled a 60,000 mol. wt protein in anterior pituitary membranes. The characteristics of [125I]CGP 23996 binding to anterior pituitary membranes were consistent with the labeling of a somatostatin receptor. Interestingly, a comparison of the [125I]CGP 23996 labeled material from striatal and anterior pituitary membranes by two-dimensional polyacrylamide gel electrophoresis revealed the presence of several striatal somatostatin receptors of varying charge (pI values between 6 and 6.5) but only a single pituitary receptor. These findings indicate that physical differences may exist between subtypes of somatostatin receptors.
利用光交联技术对脑和垂体生长抑素受体的物理特性进行了表征。使用交联剂N - 羟基琥珀酰亚胺 - 4 - 叠氮苯甲酸酯和紫外线，将大鼠纹状体和垂体前叶膜中的生长抑素受体与不可还原的生长抑素类似物[125I]CGP 23996共价结合。在纹状体膜中，一种分子量为60,000的蛋白质被[125I]CGP 23996标记。该结合被生长抑素类似物强烈抑制，但不被其他生物活性肽抑制。鸟苷三磷酸γ硫醇可减少[125I]CGP 23996对分子量为60,000蛋白质的标记，这与与鸟苷三磷酸结合蛋白偶联的生长抑素受体的标记一致。在天然十二烷基硫酸钠凝胶中，[125I]CGP 23996标记的分子量为60,000蛋白质的迁移不受还原剂二硫苏糖醇的影响，表明纹状体生长抑素受体普遍缺乏二硫键。纹状体生长抑素受体用去污剂3 - [(3 - 胆酰胺丙基)-二甲基氨基]-1 - 丙烷磺酸盐溶解，并特异性结合凝集素麦胚凝集素，表明纹状体生长抑素受体是一种糖蛋白。[125I]CGP 23996也标记了垂体前叶膜中一种分子量为60,000的蛋白质。[125I]CGP 23996与垂体前叶膜结合的特性与生长抑素受体的标记一致。有趣的是，通过二维聚丙烯酰胺凝胶电泳对来自纹状体和垂体前叶膜的[125I]CGP 23996标记物质进行比较，发现存在几种电荷不同（pI值在6至6.5之间）的纹状体生长抑素受体，但只有一种垂体受体。这些发现表明生长抑素受体亚型之间可能存在物理差异。
