title: Nucleotides regulate the binding affinity of the recombinant type A cholecystokinin receptor in CHO K1 cells.
abstract: Cholecystokinin (CCK) receptors on rat pancreatic acinar cells display two binding affinity states in the presence of adeninine and guanine triphosphates with the effect of ATP mediated by the enzyme nucleoside diphosphate kinase. To determine whether this behavior was intrinsic to a single receptor protein we studied the binding affinity of CHO cells stably transfected with a cloned rat CCKA receptor. 125I-CCK binding to intact cells at 37 degrees C revealed two affinity states for CCK of Kd values 20 pM and 2.4 nM. Membranes prepared from these cells displayed a single affinity state for CCK but two affinity states could be restored in the presence of GTP[gamma S], ATP and ATP[gamma S] but not AMP-PCP. ATP and ATP[gamma S] but not AMP-PCP were substrates for nucleoside diphosphate kinase present in CHO cell membranes and transferred their terminal phosphate to GDP. These findings indicate that the interconvertible affinity states of the CCK receptor are inherent in a single receptor protein and that nucleoside diphosphate kinase mediates the effect of ATP to regulate these two affinity states.
authors.affiliation: Department of Physiology, University of Michigan, Ann Arbor 48109-0622, USA.
authors.forename: G T
authors.initials: GT
authors.lastname: Blevins
authors.forename: E M
authors.initials: EM
authors.lastname: van de Westerlo
authors.forename: C D
authors.initials: CD
authors.lastname: Logsdon
authors.forename: P M
authors.initials: PM
authors.lastname: Blevins
authors.forename: J A
authors.initials: JA
authors.lastname: Williams
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D001667:Binding, Competitive; D016466:CHO Cells / Q000378:metabolism*; D003001:Cloning, Molecular; D006224:Cricetinae; D015870:Gene Expression / Q000235:genetics; D006160:Guanosine Triphosphate / Q000494:pharmacology; D015151:Immunoblotting; D008565:Membrane Proteins / Q000378:metabolism; D009701:Nucleoside-Diphosphate Kinase / Q000378:metabolism; D009711:Nucleotides / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects; D011949:Receptors, Cholecystokinin / Q000187:drug effects / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012844:Sincalide / Q000378:metabolism / Q000494:pharmacology; D014162:Transfection / Q000235:genetics
chemical_list: D008565:Membrane Proteins; D009711:Nucleotides; D011949:Receptors, Cholecystokinin; D011994:Recombinant Proteins; C005147:5'-adenylyl (beta,gamma-methylene)diphosphonate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D009701:Nucleoside-Diphosphate Kinase; D012844:Sincalide; C002630:alpha,beta-methyleneadenosine 5'-triphosphate