Induction of a high-affinity ketanserin binding site at the 5-Hydroxytryptamine(1B) receptor by modification of its carboxy-terminal intracellular portion.
Two chimeric 5-hydroxytryptamine (5-HT) receptors were constructed by exchanging the C-terminal portion of the human (h) 5-HT(1B) receptor with the equivalent domain of the h 5-HT(2A) receptor (5-HT(1B/2A)) or with this domain truncated from its last 44 amino acids (5-HT(1B/2ADelta44)). The equilibrium dissociation constant of the radioligand [(3)H]GR 125743 was similar for both chimera compared to the wild-type (wt) h 5-HT(1B) receptor upon transient expression in COS-7 cells. Ketanserin binding affinity was 21-fold increased from pK(i): 5.79 (wt h 5-HT(1B) receptor) to pK(i): 7.11 at the 5-HT(1B/2A) chimeric receptor, this latter value being close to that of the wt h 5-HT(1D) receptor (pK(i): 7.62). This enhanced ketanserin binding affinity was lost when the last 44 C-terminal amino acids of the 5-HT(2A) receptor were deleted in the chimera 5-HT(1B/2ADelta44) (pK(i): 5.80). The binding affinities of the 5-HT antagonists ritanserin, GR 125743, and SB-224289 were not modified at either chimeric 5-HT receptor. The agonists F 11356, 5-HT, zolmitriptan, and sumatriptan yielded slightly increased (2- to 6-fold) binding affinities at both chimera as compared to the wt h 5-HT(1B) receptor. The present data suggest a role for the C-terminal intracellular receptor domain in modifying ketanserin/5-HT(1B) receptor interactions.
Wurch
T
T
Department of Cellular and Molecular Biology, Centre De Recherche Pierre Fabre, 81106, Castres, France.
Palmier
C
C
Pauwels
P J
PJ
D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002478:Cells, Cultured; D006801:Humans; D007650:Ketanserin / Q000494:pharmacology*; D008024:Ligands; D044302:Receptor, Serotonin, 5-HT1B; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012702:Serotonin Antagonists / Q000494:pharmacology*
C470302:HTR1B protein, human; D008024:Ligands; D044302:Receptor, Serotonin, 5-HT1B; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin; D011993:Recombinant Fusion Proteins; D012702:Serotonin Antagonists; D007650:Ketanserin