TY - JOUR
T1 - Functional pharmacology of cloned heterodimeric GABA-B receptors expressed in mammalian cells
AU - Bräuner-Osborne, Hans
AU - Krogsgaard-Larsen, P
PY - 1999/12
Y1 - 1999/12
N2 - 1. In this study we report a new assay of heterodimeric gamma-amino-butanoic acid subtype B (GABAB) receptors where either GABABR1a or GABABR1b are co-expressed with GABABR2 and the chimeric G-protein Galphaq-z5 in tsA cells. In this manner we obtained a robust response to GABAB agonists measured as increase in phosphoinositide hydrolysis. 2. We used this assay to characterize a number of commonly used GABAB receptor ligands. Both splice variants displayed the same rank order of agonist potency; 3-aminopropyl(methyl)phosphinic acid (SKF-97541)>GABA>(R)-4-amino-3-(4-chlorophenyl)butanoic acid ((R)-baclofen)>(RS)-4-amino-3-(5-chloro-2-thienyl)butanoic acid (BCTG)>3-aminopropylphosphonic acid (3-APPA) and furthermore, the absolute agonist potency values were very close to each other. 3. 3-APPA was a partial agonist displaying maximal responses of 41 and 61% compared to GABA at GABABR1a and GABABR1b, respectively. The antagonist (RS)-3-amino-2-(4-chlorophenyl)-2-hydroxypropylsulphonic acid (2-OH-saclofen) displayed KB values of 15 and 7.8 microM at GABABR1a and GABABR1b, respectively. 4. The rank order of agonist potency as well as the absolute ligand potencies correspond very well with those previously reported in different tissues, and this study thus provides a functional assay of cloned GABAB receptors which should be a valuable tool for further characterization of GABAB ligands. Finally, we can conclude that the functional pharmacological profiles of the two GABABR1 splice variants are very similar.
AB - 1. In this study we report a new assay of heterodimeric gamma-amino-butanoic acid subtype B (GABAB) receptors where either GABABR1a or GABABR1b are co-expressed with GABABR2 and the chimeric G-protein Galphaq-z5 in tsA cells. In this manner we obtained a robust response to GABAB agonists measured as increase in phosphoinositide hydrolysis. 2. We used this assay to characterize a number of commonly used GABAB receptor ligands. Both splice variants displayed the same rank order of agonist potency; 3-aminopropyl(methyl)phosphinic acid (SKF-97541)>GABA>(R)-4-amino-3-(4-chlorophenyl)butanoic acid ((R)-baclofen)>(RS)-4-amino-3-(5-chloro-2-thienyl)butanoic acid (BCTG)>3-aminopropylphosphonic acid (3-APPA) and furthermore, the absolute agonist potency values were very close to each other. 3. 3-APPA was a partial agonist displaying maximal responses of 41 and 61% compared to GABA at GABABR1a and GABABR1b, respectively. The antagonist (RS)-3-amino-2-(4-chlorophenyl)-2-hydroxypropylsulphonic acid (2-OH-saclofen) displayed KB values of 15 and 7.8 microM at GABABR1a and GABABR1b, respectively. 4. The rank order of agonist potency as well as the absolute ligand potencies correspond very well with those previously reported in different tissues, and this study thus provides a functional assay of cloned GABAB receptors which should be a valuable tool for further characterization of GABAB ligands. Finally, we can conclude that the functional pharmacological profiles of the two GABABR1 splice variants are very similar.
KW - Alternative Splicing
KW - Cell Line, Transformed
KW - Cloning, Molecular
KW - Dimerization
KW - GTP-Binding Protein alpha Subunits, Gq-G11
KW - GTP-Binding Proteins
KW - Humans
KW - Kinetics
KW - Ligands
KW - Phosphatidylinositols
KW - Receptors, GABA
KW - Receptors, GABA-B
KW - Recombinant Fusion Proteins
KW - Transfection
U2 - 10.1038/sj.bjp.0702914
DO - 10.1038/sj.bjp.0702914
M3 - Journal article
C2 - 10602314
SN - 0007-1188
VL - 128
SP - 1370
EP - 1374
JO - British Journal of Pharmacology
JF - British Journal of Pharmacology
IS - 7
ER -