Characterization of human 5-HT1 receptors expressed in Sf9 insect cells

Four human 5-HT receptor subtypes (5-HT1A, 5-HT1D alpha, 5-HT1D beta and 5-HT1E) have been expressed in Sf9 insect cells. All four human 5-hydroxytryptamine receptors produced by Sf9 cells had the expected pharmacological properties. Surprisingly, levels of expression of these receptors were relatively low (1-5 pmol/mg protein). High affinity agonist binding to the four 5-hydroxytryptamine receptors was reduced to different extents by guanine nucleotides and/or NaCl. This suggests that the nature of receptor-G protein coupling and/or the predominant conformational state of the receptors in Sf9 cell membranes varies among the different receptors. Activation of all four receptors inhibited forskolin-stimulated cAMP formation in intact Sf9 cells. Expression of 5-hydroxytryptamine receptors in Sf9 cells should be useful for purification of these receptors, for studies of post-translational modification and for pharmaceutical screening.