Multiple affinity forms of the calcitonin gene-related peptide receptor in rat cerebellum

Journal Article · Sat Jun 01 00:00:00 EDT 1991 · Molecular Pharmacology; (United States)

OSTI ID:5398401

Chatterjee, T K; Fisher, R A ^[1]

---

1. Department of Pharmacology, University of Iowa, College of Medicine, Iowa City (USA)

Binding of 125I-calcitonin gene-related peptide (125I-CGRP) to rat cerebellum membranes and the sensitivity to guanine nucleotides of binding were investigated. Cerebellum binding sites labeled by 125I-CGRP appear to be highly specific, inasmuch as CGRP inhibited binding with an IC50 of 100 pM but other peptides were inactive or much less active in displacing 125I-CGRP from these sites. 125I-CGRP binding sites in cerebellum membranes were saturable and of high affinity. Scatchard analysis of the saturation binding data revealed a homogeneous population of binding sites, with a KD of 224 {plus minus} 28 pM and Bmax of 131 {plus minus} 15 fmol/mg of protein. In the presence of guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) (100 microM), a single population of binding sites, with a KD of 464 {plus minus} 77 pM and Bmax of 100 {plus minus} 14 fmol/mg of protein, was observed. The kinetics of association of 125I-CGRP with cerebellum membranes were monophasic at all ligand concentrations tested. However, the observed association rate constant (kobs) was not dependent on (125I-CGRP) in a linear fashion in either the absence or the presence of GTP gamma S (100 microM). The kinetics of dissociation of 125I-CGRP from cerebellum membranes were multiexponential, with fast and slow dissociating components having rate constants of 0.34 {plus minus} 0.01 and 0.025 {plus minus} 0.001 min-1, respectively. The fast dissociating component represented 60 {plus minus} 2% of the total specific binding sites. Dissociation of 125I-CGRP from cerebellum sites was much faster in the presence of GTP gamma S (100 microM) but still exhibited dissociation from two affinity components. The rate constants for these components of dissociation were 0.67 {plus minus} 0.03 and 0.077 {plus minus} 0.007 min-1, with the faster dissociating component representing 66 {plus minus} 1% of the total specific binding sites.

• OSTI ID: 5398401
• Journal Information: Molecular Pharmacology; (United States), Journal Name: Molecular Pharmacology; (United States) Vol. 39:6; ISSN 0026-895X; ISSN MOPMA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
ANIMALS
AROMATICS
AZAARENES
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOCHEMISTRY
BODY
BRAIN
CALCITONIN
CELL CONSTITUENTS
CELL MEMBRANES
CENTRAL NERVOUS SYSTEM
CEREBELLUM
CHEMISTRY
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
GENES
GUANOSINE
HETEROCYCLIC COMPOUNDS
HORMONES
IN VITRO
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
NERVOUS SYSTEM
NUCLEI
NUCLEOSIDES
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PEPTIDE HORMONES
PEPTIDES
POLYPEPTIDES
PROTEINS
PURINES
RADIOISOTOPES
RATS
REACTION KINETICS
RECEPTORS
RIBOSIDES
RODENTS
TRACER TECHNIQUES
VERTEBRATES