Alternative splicing of a Drosophila GABA receptor subunit gene identifies determinants of agonist potency.
Alternative splicing of the Drosophila melanogaster Rdl gene yields four ionotropic GABA receptor subunits. The two Rdl splice variants cloned to date, RDL(ac) and RDL(bd) (DRC17-1-2), differ in their apparent agonist affinity. Here, we report the cloning of a third splice variant of Rdl, RDL(ad). Two-electrode voltage clamp electrophysiology was used to investigate agonist pharmacology of this expressed subunit following cRNA injection into Xenopus laevis oocytes. The EC(so) values for GABA and its analogues isoguvacine, muscimol, isonipecotic acid and 3-amino sulphonic acid on the RDL(ad) homomeric receptor differed from those previously described for RDL(ac) and DRC17-1-2 receptors. In addition to providing a possible physiological role for the alternative splicing of Rdl, these data delineate a hitherto functionally unassigned region of the N-terminal domain of GABA receptor subunits, which affects agonist potency and aligns closely with known determinants of potency in nicotinic acetylcholine receptors. Thus, using expression in Xenopus oocytes, we have demonstrated differences in agonist potency for the neurotransmitter GABA (and four analogues) between splice variant products of the Drosophila melanogaster Rdl gene encoding homomer-forming GABA receptor subunits.
Babraham Institute, Laboratory of Molecular Signalling, Department of Zoology, University of Cambridge, Downing Street, CB2 3EJ, Cambridge, UK.
A M
AM
Hosie
S D
SD
Buckingham
J K
JK
Presnail
D B
DB
Sattelle
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics*; D004625:Embryo, Nonmammalian; D005091:Exons; D005260:Female; D018755:GABA Agonists / Q000494:pharmacology*; D015723:Gene Library; D014644:Genetic Variation; D066298:In Vitro Techniques; D007539:Isonicotinic Acids / Q000494:pharmacology; D007540:Isonipecotic Acids / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008969:Molecular Sequence Data; D009118:Muscimol / Q000494:pharmacology; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D021122:Protein Subunits; D011963:Receptors, GABA-A / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D011994:Recombinant Proteins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D013451:Sulfonic Acids / Q000494:pharmacology; D014982:Xenopus laevis; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology*
D029721:Drosophila Proteins; D018755:GABA Agonists; D007539:Isonicotinic Acids; D007540:Isonipecotic Acids; D021122:Protein Subunits; C082030:Rdl protein, Drosophila; D011963:Receptors, GABA-A; D011994:Recombinant Proteins; D013451:Sulfonic Acids; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; C005741:sulfamic acid; C015300:isoguvacine