title: Demonstration of functional coupling between gamma -aminobutyric acid (GABA) synthesis and vesicular GABA transport into synaptic vesicles.
abstract: l-Glutamic acid decarboxylase (GAD) exists as both membrane-associated and soluble forms in the mammalian brain. Here, we propose that there is a functional and structural coupling between the synthesis of gamma-aminobutyric acid (GABA) by membrane-associated GAD and its packaging into synaptic vesicles (SVs) by vesicular GABA transporter (VGAT). This notion is supported by the following observations. First, newly synthesized [(3)H]GABA from [(3)H]l-glutamate by membrane-associated GAD is taken up preferentially over preexisting GABA by using immunoaffinity-purified GABAergic SVs. Second, the activity of SV-associated GAD and VGAT seems to be coupled because inhibition of GAD also decreases VGAT activity. Third, VGAT and SV-associated Ca(2+)calmodulin-dependent kinase II have been found to form a protein complex with GAD. A model is also proposed to link the neuronal stimulation to enhanced synthesis and packaging of GABA into SVs.
authors.affiliation: Departments of Molecular Biosciences and Medicinal Chemistry, University of Kansas, Lawrence, KS 66045, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Jin
authors.forename: Heng
authors.initials: H
authors.lastname: Wu
authors.forename: Gregory
authors.initials: G
authors.lastname: Osterhaus
authors.forename: Jianning
authors.initials: J
authors.lastname: Wei
authors.forename: Kathleen
authors.initials: K
authors.lastname: Davis
authors.forename: Di
authors.initials: D
authors.lastname: Sha
authors.forename: Eric
authors.initials: E
authors.lastname: Floor
authors.forename: Che-Chang
authors.initials: CC
authors.lastname: Hsu
authors.forename: Richard D
authors.initials: RD
authors.lastname: Kopke
authors.forename: Jang-Yen
authors.initials: JY
authors.lastname: Wu
mesh_terms: D000818:Animals; D001692:Biological Transport; D001921:Brain / Q000378:metabolism*; D005968:Glutamate Decarboxylase / Q000378:metabolism*; D018698:Glutamic Acid / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008959:Models, Neurological; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013572:Synaptic Vesicles / Q000502:physiology* / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D011993:Recombinant Fusion Proteins; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase