Channel gating in the absence of agonist by a homooligomeric molluscan GABA receptor expressed inXenopus oocytes from a cloned cDNA

Bhandal, Narotam S.; Ramsey, Robert L.; Harvey, Robert J.; Darlison, Mark G.; Usherwood, Peter N. R.

Abstract

We have previously described the isolation of a complementary DNA (cDNA) from the freshwater molluscLymnaea stagnalis encoding a polypeptide that exhibits ∼50{%} identity to the {ß}-subunits of vertebrate $γ$-aminobutyric acid (GABA) type A (GABAA) receptor. When expressed inXenopus laevis oocytes fromin vitro-transcribed RNA, the snail subunit forms functional homo-oligomeric receptors possessing chloride-selective ion channels. In recordings from voltage-clamped oocytes held at −60 mV, GABA induced an inward current, whereas application of the chloride-channel blocker picrotoxin (in the absence of agonist) elicited an apparent outward current. Single channel recordings obtained from cell-attached patches have revealed a single population of ∼20 pS channels, with an open probability greater than 90{%} (at a pipette potential of −100 mV) in the absence of GABA. The relationship between single channel current and pipette potential was linear over the studied range (−100 mV to +60 mV), but the open probability was less for hyperpolarizations than for depolarizations. The spontaneous channel openings were blocked by micromolar concentrations of picrotoxin. Functional hetero-oligomeric receptors were formed when the molluscan subunit was co-expressed in oocytes with the bovine GABAA receptor $α$1-subunit, but the channels gated by these receptors did not open spontaneously.

Citation

Bhandal, N. S., Ramsey, R. L., Harvey, R. J., Darlison, M. G., & Usherwood, P. N. R. (1995). Channel gating in the absence of agonist by a homooligomeric molluscan GABA receptor expressed inXenopus oocytes from a cloned cDNA. Invertebrate Neuroscience, 1(3), 267-272. https://doi.org/10.1007/bf02211028

• Journal Article Type: Article
• Acceptance Date: Oct 23, 1995
• Publication Date: 1995-12
• Deposit Date: Jul 27, 2016
• Journal: Invertebrate Neuroscience
• Print ISSN: 1354-2516
• Electronic ISSN: 1439-1104
• Publisher: BMC
• Peer Reviewed: Peer Reviewed
• Volume: 1
• Issue: 3
• Pages: 267-272
• DOI: https://doi.org/10.1007/bf02211028
• Keywords: GABA receptors, mollusc (Lymnaea stagnalis), picrotoxin, single-channel recordings, spontaneous channel openings, Xenopus oocytes
• Public URL: http://researchrepository.napier.ac.uk/Output/317723
• Publisher URL: http://dx.doi.org/10.1007/BF02211028