Abstract
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 Y1binding was sensitive to guanine nucleotide-binding protein (G protein) agonist and antagonist nucleotides, with the rank order of guanosine 5′-O-(thiotriphosphate) (GTPγS) > 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 μM 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 GTPγS. 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.
Footnotes
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Send reprint requests to: Steven L. Parker, Ph.D., Assistant Professor of Pharmacology, Department of Pharmacology, University of Tennessee College of Medicine, 874 Union Avenue, Memphis TN 38163. E-mail: SLParker{at}utmem1.utmem.edu
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↵1 This research was supported by National Institutes of Health grant HD13703 (W.R.C.).
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↵2 Portions of this research were reported in a preliminary form at the annual meetings of the Society for Neuroscience in 1994 (abstract #376.11), 1995 (abstract #402.1), 1996 (abstract #661.9), and 1997 (abstract #383.5).
- Abbreviations:
- NPY
- neuropeptide Y
- PYY
- peptide YY
- LP-PYY
- (Leu31,Pro34) human peptide YY
- PYY(3-36)
- human peptide YY(3-36)
- rPP
- rat pancreatic polypeptide
- hPP
- human pancreatic polypeptide
- PAR1
- parietal cortex area 1
- PIR
- piriform cortex
- AHA
- anterior hypothalamus
- HIPP
- hippocampus
- EIPA
- ethylisopropylamiloride
- GTPγS
- guanosine 5′-O-(3-thiotriphosphate)
- GDPβS
- guanosine 5′-O-(2-thiodiphosphate)
- ATPγS
- adenosine 5′-O-(3-thiotriphosphate)
- ADPβS
- adenosine 5′-O-(3-thiodiphosphate)
- PIP2
- phosphatidylinositol-4.5-bisphosphate
- Received November 25, 1997.
- Accepted March 26, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
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