TY - JOUR T1 - Impaired Resensitization and Recycling of the Cholecystokinin Receptor by Co-expression of its Second Intracellular Loop JF - Molecular Pharmacology JO - Mol Pharmacol SP - 1424 LP - 1433 DO - 10.1124/mol.58.6.1424 VL - 58 IS - 6 AU - Xi-Qin Ding AU - Rammohan V. Rao AU - Susan M. Kuntz AU - Eileen L. Holicky AU - Laurence J. Miller Y1 - 2000/12/01 UR - http://molpharm.aspetjournals.org/content/58/6/1424.abstract N2 - Intermolecular interaction represents an important theme in regulation of intracellular trafficking of organelles that can be interrupted by competitive overexpression of a relevant molecular domain. We attempted to identify the functional importance of intracellular domains of the cholecystokinin (CCK) receptor by their over-expression in receptor-bearing Chinese hamster ovary (CHO-CCKR) cell lines. Although clathrin-dependent endocytosis and recycling of this receptor are well-established (J Cell Biol 128:1029–1042, 1995), any influence of distinct receptor domains is not understood. In this work, constructs representing each of the intracellular domains of the CCK receptor were coexpressed with wild-type receptor, and stable clonal cell lines were selected. Each was characterized for ligand binding and agonist-stimulated biological activity (inositol 1,4,5-trisphosphate generation), desensitization, resensitization, receptor internalization, and recycling. Each cell line expressed normal CCK radioligand binding, signaling, internalization, and desensitization. Three independent cell lines that coexpressed the 25-residue second intracellular loop domain exhibited deficient resensitization. In morphological assessment of receptor trafficking, this construct was also shown to interfere with receptor recycling to the plasma membrane. As a control, recycling of an unrelated G protein-coupled receptor was demonstrated to occur normally in this cell line. These observations suggest that rather than representing passive cargo within an endosome, a receptor can influence its own trafficking within the cell. ER -