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Abstract
The ligand binding and G-protein coupling of the bovine hippocampal 5-HT1A receptor as a function of temperature was monitored. There is an almost complete and irreversible loss in agonist binding at 50°C. However, the antagonist binding is reduced only by 50%, and this could be reversed if the temperature is lowered to 25°C. Interestingly, the agonist binding of the 5-HT1A receptor in membranes exposed to 50°C is inhibited to a much lesser extent by GTP-γ-S, a non-hydrolysable analogue of GTP, indicating uncoupling of the 5-HT1A receptor to G-proteins at 50°C. We propose that high temperature selectively and irreversibly inactivates G-proteins thereby affecting G-protein-receptor interaction and agonist binding of the 5-HT1A receptor.
BCA, bicinchoninic acid; BSA, bovine serum albumin; GTP-γ-S, guanosine-5′-O-(3-thiotriphosphate); 5-HT, 5-hydroxytryptamine; 8-OH-DPAT, 8-hydroxy-2-(di-N-propylamino)tetralin; p-MPPF, 4-(2′-methoxy)-phenyl-1-[2′-(N-2′′-pyridinyl)-p-fluorobenzamido]ethyl-piperazine; p-MPPI, 4-(2′-methoxy)-phenyl-1-[2′-(N-2′′-pyridinyl)-p-iodobenzamido]ethyl-piperazine; PMSF, phenylmethylsulfonyl fluoride; Tris, tris-(hydroxymethyl)aminomethane
BCA, bicinchoninic acid; BSA, bovine serum albumin; GTP-γ-S, guanosine-5′-O-(3-thiotriphosphate); 5-HT, 5-hydroxytryptamine; 8-OH-DPAT, 8-hydroxy-2-(di-N-propylamino)tetralin; p-MPPF, 4-(2′-methoxy)-phenyl-1-[2′-(N-2′′-pyridinyl)-p-fluorobenzamido]ethyl-piperazine; p-MPPI, 4-(2′-methoxy)-phenyl-1-[2′-(N-2′′-pyridinyl)-p-iodobenzamido]ethyl-piperazine; PMSF, phenylmethylsulfonyl fluoride; Tris, tris-(hydroxymethyl)aminomethane