Functional pharmacology of cloned heterodimeric GABA-B receptors expressed in mammalian cells

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 -