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Modulation of 5‐Hydroxytryptamine 1A Receptor Density by Nonhydrolyzable GTP Analogues
Author(s) -
Harrington Melissa A.,
Peroutka Stephen J.
Publication year - 1990
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1990.tb13314.x
Subject(s) - gtp' , guanine , g protein , nucleotide , binding site , receptor , membrane , chemistry , stereochemistry , biophysics , biochemistry , biology , enzyme , gene
Co‐incubation of rat cortical membranes with 10 ‐4 M GTP results in a competitive inhibition of 5‐hydroxytryptamine 1A (5‐HT 1A ) receptor binding sites labeled by [ 3 H]8‐hydroxy‐2‐(di‐ n ‐propylamino)tetralin ([ 3 H]8‐OH‐DPAT). Preincubation of cortical membranes with 10 ‐4 M GTP does not significantly change either K D or B max values, indicating that the effect of GTP is reversible. By contrast, GTPγS and 5′‐guanylylimidodiphosphate (GppNHp) are nonhydrolyzable analogues of GTP which lengthen the time course of guanine nucleotide activation of guanine nucleotide binding proteins (G proteins) and thereby alter G protein‐receptor interactions. These nonhydrolyzable GTP analogues were used to characterize the effects of persistent alterations in G proteins on [ 3 H]8‐OH‐DPAT binding to 5‐HT 1A receptors. Co‐incubation of rat cortical membranes with either 10 ‐4 M GTPγS or GppNHp results in a decrease in both the affinity and apparent density of 5‐HT 1A binding sites. Co‐incubation with the nonhydrolyzable nucleotides reduces the affinity of [ 3 H]8‐OH‐DPAT binding by 65‐70% and lowers the density of the binding site by 53‐61%. Similarly, preincubation of membranes with a 10 ‐4 M concentration of either GTPγS or GppNHp significantly increases the K D value and reduces the B max value of [ 3 H]8‐OH‐DPAT binding. These results indicate that GTPγS and GppNHp induce persistent changes in 5‐HT 1A receptor‐G protein interactions that are reflected as a decrease in the density of binding sites labeled by [ 3 H]8‐OH‐DPAT.