Molecular Characteristics and Peptide Specificity of Vasoactive Intestinal Peptide Receptors from Rat Cerebral Cortex

Publisher Website
Google Scholar
Abstract
Vasoactive intestinal peptide (VIP) receptors have been identified in CNS by their chemical specificity and molecular size. Using synaptosomes isolated from rat cerebral cortex, it was shown that central VIP receptors discriminated among natural and synthetic VIP-related peptides, because half-maximal inhibition of [125I]VIP binding to synaptosomes was obtained for 0.6 nM VIP, 9 nM peptide histidine isoleucineamide (PHI), 50 nM VIP 2–28, 70 nM secretin, 100 nM rat growth hormone-releasing factor (GRF), and 350 nM human GRF. Other peptides of the VIP family, such as glucagon and gastric inhibitory polypeptide, did not interact with cortical VIP receptors. The molecular components of VIP receptors in rat cerebral cortex were identified after [125I]VIP cross-linking to synaptosomes using the cross-linker dithiobis(succinimidyl propionate). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of synaptosomal proteins revealed two major [125I]VIP-pro-tein complexes of Mr 49,000 and 18,000. The labeling of the Mr49,000 component was specific, because it was abolished by native VIP, whereas the labeling of the Mr 18,000 component was not. Natural VIP agonists reduced the labeling of the Mr49,000 component with the following order of potency: VIP > PHI > secretin ∼ rat GRF. In contrast, glucagon and octapeptide of cholecystokinin were without effect, a result indicating its peptide specificity. Densitometric scanning of autoradiographs showed that the labeling of the Mr 49,000 component was inhibited by low VIP concentrations between 10−-10 and 10−-6M (IC50= 0.8 nM), a result indicating the component's high affinity for VIP. Labeling was also reduced by GTP in the concentration range between 10−-7 and 10−-3M (ED50= 5 μM). Assuming that one molecule of [125I]VIP is bound per molecule of synaptosomal protein, a major protein of Mr 46,000 was identified as a component of the VIP receptor in rat cerebral cortex.

This publication has 37 references indexed in Scilit: