The serotonin1A receptor is the most extensively studied member of the family of seven transmembrane domain G-protein coupled serotonin receptors. Since a large portion of such transmembrane receptors remains in contact with the membrane lipid environment, lipid–protein interactions assume importance in the structure-function analysis of such receptors. We have earlier reported the requirement of cholesterol for serotonin1A receptor function in native hippocampal membranes by specific depletion of cholesterol using methyl- β-cyclodextrin. In this paper, we monitored the serotonin1A receptor function in membranes that are enriched in cholesterol using a complex prepared from cholesterol and methyl-β-cyclodextrin. Our results indicate that ligand binding and receptor/G-protein interaction of the serotonin1A receptor do not exhibit significant difference in native and cholesterol-enriched hippocampal membranes indicating that further enrichment of cholesterol has little functional consequence on the serotonin1A receptor function. These results therefore provide new information on the effect of cholesterol enrichment on the hippocampal serotonin1A receptor function.
Abbreviations: BCA, bicinchoninic acid; DMPC, dimyristoyl-sn-glycero-3-phosphocholine; GPCR, G-protein coupled receptor; GTP-γ-S, guanosine-5′-O-(3-thiotriphosphate); MβCD, methyl-β-cyclodextrin; 5-HT, 5-hydroxytryptamine (serotonin); 5-HT1A receptor, 5-hydroxytryptamine-1A receptor; 8-OH-DPAT, 8-hydroxy-2(di-N-propylamino) tetralin; p-MPPI, 4-(2′-methoxy)-phenyl-1-[2′-(N-2′′-pyridinyl)-p-iodobenzamido] ethyl-piperazine; PMSF, phenylmethylsulfonyl fluoride; p-MPPF, 4-(2′-methoxy)-phenyl-1-[2′-(N-2′′-pyridinyl)-p-fluorobenzamido]ethyl-piperazine