Kreuzer O J, Krisch B, Déry O, Bunnett N W, Meyerhof W
Deutsches Institut für Ernährungsforschung, Abteilung Molekulare Genetik und Universität Potsdam, Arthur-Schuenert-Allee 114-116, D-14558 Potsdam-Rehbrücke, Germany.
J Neuroendocrinol. 2001 Mar;13(3):279-87. doi: 10.1046/j.1365-2826.2001.00630.x.
Agonist-induced endocytosis of somatostatin receptors determines subsequent cellular responsiveness to peptide agonist and influences somatostatin receptor scintigraphy, a technique to image various tumours. We examined the internalization of sst3HSV, an epitope-tagged type 3 somatostatin receptor, in transfected rat neuroendocrine insulinoma cells. Stimulation of these cells with somatostatin induced trafficking of coexpressed enhanced green fluorescence protein/beta-arrestin1 fusion protein and sst3HSV to colocalize in the same endocytic vesicles. Coexpression of a dominant negative mutant of the arrestin fusion protein with the receptor blocked the internalization of sst3HSV. Stimulation with somatostatin also induced the transient translocation of alpha-adaptin, a component of the adaptor protein complex 2, to the plasma membrane. alpha-adaptin and clathrin colocalized with the receptor. By electron microscopy, we observed internalized sst3 in clathrin coated pits, endosomes and at the limiting membrane of multivesicular bodies, a location typical for receptors being recycled. Concordantly, we observed sst3HSV colocalized with Rab11 in a perinuclear compartment which is likely to correspond to the pericentriolar recycling endosome. Thus, agonist-induced endocytosis of sst3 depends on its interaction with beta-arrestin, involves the adaptor protein complex 2 and proceeds via clathrin coated vesicles to the recycling compartment.
生长抑素受体的激动剂诱导内吞作用决定了细胞随后对肽类激动剂的反应性，并影响生长抑素受体闪烁扫描术，这是一种用于对各种肿瘤进行成像的技术。我们研究了转染的大鼠神经内分泌胰岛素瘤细胞中sst3HSV（一种表位标记的3型生长抑素受体）的内化情况。用生长抑素刺激这些细胞可诱导共表达的增强型绿色荧光蛋白/β-抑制蛋白1融合蛋白和sst3HSV转运至同一内吞小泡中共定位。抑制蛋白融合蛋白的显性负突变体与该受体共表达可阻断sst3HSV的内化。用生长抑素刺激还可诱导衔接蛋白复合物2的一个组分α-衔接蛋白短暂转位至质膜。α-衔接蛋白和网格蛋白与该受体共定位。通过电子显微镜，我们观察到内化的sst3存在于网格蛋白包被小窝、内体以及多囊泡体的限制膜处，这是受体进行再循环的典型位置。与此一致的是，我们观察到sst3HSV与Rab11在一个核周区室中共定位，该区域可能对应于中心粒周再循环内体。因此，激动剂诱导的sst3内吞作用取决于其与β-抑制蛋白的相互作用，涉及衔接蛋白复合物2，并通过网格蛋白包被小泡转运至再循环区室。
