Characterization of G protein and phospholipase C-coupled agonist binding to the Y1 neuropeptide Y receptor in rat brain: sensitivity to G protein activators and inhibitors and to inhibitors of phospholipase C.
Binding of a Y1-subtype-selective agonist of neuropeptide Y (NPY) receptor, (Leu31,Pro34)human peptide YY (LP-PYY), to particulates from four rat brain areas (parietal cortex area 1, piriform cortex, anterior hypothalamus and hippocampus) showed a distinct response to LP-PYY and PYY, a uniformly low sensitivity to ligands selective for the Y2, Y4 and Y5 NPY receptor subtypes and high sensitivity to a Y1 site-selective antagonist, BIBP-3226. The Y1 binding was sensitive to guanine nucleotide-binding protein (G protein) agonist and antagonist nucleotides, with the rank order of guanosine 5'-O-(thiotriphosphate) (GTP gamma S) > GTP > GDP > guanosine 5'-O-(thiodiphosphate). However, guanine nucleotides did not affect about one third of the specific Y1 binding. Most of Y1 binding could be inhibited by a G protein nucleotide site/docking site receptor mimic, mastoparan analog MAS-7. In all areas examined, the Y1 binding of LP-PYY was little affected by up to 100 microM of the antagonists of K+, Na+ and Ca++ channels, protein kinase C, phospholipase A2, phospholipase D and phosphatidylinositol 3-kinase, phospholipase substrate phospholipids, steroids or detergents. However, the binding was potently inhibited by phospholipase C inhibitors (especially the aminosteroid U-73122), which also dissociated the bound Y1 ligand in steady-state conditions. U-73122 also displaced the Y1 binding insensitive to GTP gamma S. Ligand association with the brain Y1 NPY receptor thus strongly depends on activity of both G proteins and phospholipase C, implying specific interactions of these transducers/effectors with the receptor molecule in ligand binding. A portion of brain Y1 sites could be directly coupled to phospholipase(s) C.
Parker
S L
SL
Department of Pharmacology, University of Tennessee School of Medicine, Memphis 38163, USA. SLParker.utmem1.utmem.edu
Parker
M S
MS
Sweatman
T
T
Crowley
W R
WR
D000818:Animals; D001921:Brain / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004963:Estrenes / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D019894:Peptide YY / Q000378:metabolism*; D011224:Prazosin / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D017476:Receptors, Neuropeptide Y / Q000819:agonists / Q000378:metabolism*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000502:physiology*
D004791:Enzyme Inhibitors; D004963:Estrenes; D011760:Pyrrolidinones; D017476:Receptors, Neuropeptide Y; D019894:Peptide YY; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D006160:Guanosine Triphosphate; D011493:Protein Kinase C; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D011224:Prazosin