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Title: Characterization of a GABA<inf>A</inf>receptor β subunit in the abalone Haliotis asinina that is upregulated during larval development
Authors: Praphaporn Stewart
Elizabeth A. Williams
Michael J. Stewart
Nantawan Soonklang
Sandie M. Degnan
Scott F. Cummins
Peter J. Hanna
Prasert Sobhon
Faculty of Medicine, Thammasat University
University of Queensland
Max Planck Institute for Developmental Biology
University of Tasmania
Deakin University
University of the Sunshine Coast
Mahidol University
Keywords: Agricultural and Biological Sciences
Issue Date: 15-Dec-2011
Citation: Journal of Experimental Marine Biology and Ecology. Vol.410, (2011), 53-60
Abstract: In the tropical abalone Haliotis asinina, the neurotransmitter γ-aminobutyric acid (GABA) is a potent inducer of larval settlement, a process beginning with the onset of a behavioral search for a suitable substratum and ending with metamorphosis. In the natural environment, larvae can encounter GABA or GABA-like molecules through association with conspecific foot mucus and crustose coralline algae. To understand the role of GABA in the molecular process leading to settlement required identification and analysis of GABA's cognate receptor. We now have isolated the first abalone full-length GABA A receptor (Has-GABA A R) β subunit gene, which encodes a protein of 485 amino acids, from juvenile H. asinina neural tissue. Similar to other metazoan GABA A Rs, the abalone GABA A R contains four transmembrane domains, a conserved cysteine loop in the N-terminal extra-cellular domain, and highly conserved sequence motifs. The Has-GABA A R gene is expressed at extremely low levels in unfertilized eggs, but increases significantly just prior to settlement, peaking at 120h post fertilization (hpf). We further demonstrate that during the period of larval competence (96-144hpf), gene transcripts and the encoded Has-GABA A R were localized in a cluster of cells along the dorsal and lateral edges of the foot, as well as the posterior epithelium. In functional settlement assays using GABA and 5-AVA, we found that there was significantly lower settlement of veligers pre-treated with antibodies to an external domain of the Has-GABA A R than those treated with preimmune serum, or untreated veligers. We postulate that this receptor may act as a highly sensitive chemical sensor, whose activation is necessary to trigger chloride-mediated sensory neuron activation or inhibition, leading to the initiation of settlement and metamorphosis events. © 2011 Elsevier B.V.
ISSN: 00220981
Appears in Collections:Scopus 2011-2015

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