Hajri A, Koenig M, Balboni G, Damgé C
Institut de Recherche sur les Cancers de l'Appareil Digestif, Hôpitaux Universitaires, Strasbourg, France.
Pancreas. 1996 Jan;12(1):25-35. doi: 10.1097/00006676-199601000-00004.
The biochemical and pharmacological characteristics of specific binding sites for gastrin-releasing peptide (GRP) were investigated in normal exocrine pancreas and in an azaserine-induced pancreatic carcinoma in the rat, under similar experimental conditions. Cells from both types of tissues contained rapid, reversible, temperature-dependent, and highly specific binding sites for GRP. Scatchard analysis of equilibrium data obtained with normal and tumor plasma membranes indicated a single class of high-affinity sites (KD = 0.42 +/- 0.06 and 0.35 +/- 0.05 nM, respectively), but the number of GRP receptors was significantly different (Bmax = 31 +/- 4.5 and 189 +/- 20 fmol/mg protein, respectively). Binding of 125I-GRP1-27 was sensitive to GTP analogues, suggesting that the GRP receptor is functionally linked to a guanyl regulatory protein; however, the wheat germ agglutinin-agarose purified receptor had lost this G-protein activity. Cross-linking of 125I-GRP1-27 either to normal and neoplastic cells or to crude membranes, solubilized membrane proteins, and partially purified receptors revealed the presence of a specific MW 75-kDa polypeptide. N-Glycanase treatment reduced this apparent MW to about 45 kDa. Together, these data suggest that normal and tumor pancreatic cells contain a specific GRP receptor that is expressed more on malignant pancreatic tissues.
在相似的实验条件下，研究了胃泌素释放肽（GRP）特异性结合位点在正常大鼠外分泌胰腺和氮杂丝氨酸诱导的大鼠胰腺癌中的生化及药理学特性。两种组织类型的细胞均含有对GRP快速、可逆、温度依赖性且高度特异性的结合位点。对正常和肿瘤细胞膜获得的平衡数据进行Scatchard分析表明存在单一类高亲和力位点（KD分别为0.42±0.06和0.35±0.05 nM），但GRP受体数量存在显著差异（Bmax分别为31±4.5和189±20 fmol/mg蛋白）。125I-GRP1-27的结合对GTP类似物敏感，提示GRP受体在功能上与鸟苷调节蛋白相连；然而，麦胚凝集素-琼脂糖纯化的受体已丧失这种G蛋白活性。将125I-GRP1-27与正常和肿瘤细胞或粗膜、可溶性膜蛋白及部分纯化的受体进行交联，揭示存在一种特异性的分子量75 kDa多肽。N-糖苷酶处理使该表观分子量降至约45 kDa。这些数据共同表明，正常和肿瘤胰腺细胞含有一种特异性GRP受体，其在恶性胰腺组织上表达更多。
