Luis J, Martin J M, el Battari A, Marvaldi J, Pichon J
Institut de Chimie Biologique, Université de Provence, Marseille, France.
Biochimie. 1988 Oct;70(10):1311-22. doi: 10.1016/0300-9084(88)90002-8.
Vasoactive intestinal peptide (VIP) is a neuropeptide with a broad range of biological activities in various tissues. After interaction with its membrane receptor, VIP generally induces a very large increase in the intracellular cyclic AMP level. Receptors for VIP have been described in numerous tissues and cell lines. The first results on VIP receptor structure have been obtained by covalent cross-linking using bifunctional reagents. The molecular mass of the different components characterized in this way differs greatly according to the species and the tissue used. This heterogeneity may reflect either a difference in the length of the cross-linked polypeptide backbone or differently glycosylated forms of the same polypeptide. The VIP binding site of intact human adenocarcinoma cells (HT29 cells) is an Mr 64,000 glycoprotein with 20kDa of N-linked oligosaccharide side chains containing sialic acid. The structure of the VIP binding site from HT29 cell is compared, first to the structure of the VIP receptor from other tissues, particularly that from rat liver, and second to the structure of the hepatic glucagon binding site. Recently, solubilization of the VIP receptor in an active form has provided a new way of studying this receptor. The HT29 cell line is an appropriate model to study the dynamics of the VIP receptor. After binding to its receptor, VIP is rapidly internalized, probably by receptor-mediated endocytosis. This internalization leads to a decrease in the cell surface receptor number and simultaneously to a homologous desensitization of adenylate cyclase. VIP is then degraded in the lysosomes, while most of the receptors are recycled back to the cell surface. The presence of an intracellular pool of unoccupied VIP receptors has been demonstrated after inactivation of the cell surface receptors by chymotrypsin. The kinetics of the receptor reappearance at the cell surface, after inactivation by chymotrypsin or after receptor-mediated endocytosis, indicate 2 possible intracellular pathways for occupied and unoccupied VIP receptors.
血管活性肠肽（VIP）是一种在多种组织中具有广泛生物活性的神经肽。与膜受体相互作用后，VIP通常会使细胞内环状AMP水平大幅升高。VIP受体已在众多组织和细胞系中被描述。通过使用双功能试剂进行共价交联，已获得了关于VIP受体结构的首批结果。以这种方式表征的不同组分的分子量根据所使用的物种和组织而有很大差异。这种异质性可能反映了交联多肽主链长度的差异，或者同一多肽不同的糖基化形式。完整的人腺癌细胞（HT29细胞）的VIP结合位点是一种分子量为64,000的糖蛋白，其N-连接的寡糖侧链含有20kDa的唾液酸。首先将HT29细胞的VIP结合位点结构与其他组织（特别是大鼠肝脏）的VIP受体结构进行比较，其次与肝胰高血糖素结合位点的结构进行比较。最近，以活性形式溶解VIP受体为研究该受体提供了一种新方法。HT29细胞系是研究VIP受体动力学的合适模型。与受体结合后，VIP会迅速内化，可能是通过受体介导的内吞作用。这种内化导致细胞表面受体数量减少，同时导致腺苷酸环化酶的同源脱敏。然后VIP在溶酶体中被降解，而大多数受体则被循环回到细胞表面。在用胰凝乳蛋白酶使细胞表面受体失活后，已证明存在细胞内未占据的VIP受体池。在用胰凝乳蛋白酶失活或受体介导的内吞作用后，受体在细胞表面重新出现的动力学表明，占据和未占据的VIP受体存在两种可能的细胞内途径。
