Role of glutamate decarboxylase (GAD) isoform, GAD65, in GABA synthesis and transport into synaptic vesicles-Evidence from GAD65-knockout mice studies.
In GAD65-knockout mice, lack of GAD65 expression was confirmed. The expression level of vesicular GABA transporter (VGAT) was upregulated, and no change in the synaptic vesicles (SV)-associated GAD67 was found. GAD65(-/-) SV transported cytosolic GABA much more efficiently than that of the wild type, further supporting our model that there is a structural and functional coupling between GABA synthesis and packaging into SV. Both full-length and truncated forms of GAD65 could bind to GABAergic SV, indicating the N-terminus is not required for the anchoring of GAD65 to SV. Although both GAD65(-/-) SV reconstituted with either GAD65 or GAD67 could synthesize GABA from [3H] glutamate and transport this newly synthesized GABA into SV, the combined evidence suggests that GAD65 plays a major role in GABA transmission in normal physiological condition. However, GAD67 could serve this role under some pathological conditions.
Wu
Heng
H
Department of Biomedical Science, Florida Atlantic University, Boca Raton, FL 33431, USA.
Jin
Ying
Y
Buddhala
Chandana
C
Osterhaus
Gregory
G
Cohen
Eric
E
Jin
Hong
H
Wei
Jianning
J
Davis
Kathleen
K
Obata
Kunihiko
K
Wu
Jang-Yen
JY
D000818:Animals; D005786:Gene Expression Regulation / Q000235:genetics*; D005968:Glutamate Decarboxylase / Q000172:deficiency / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism; D007527:Isoenzymes / Q000172:deficiency / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D021381:Protein Transport / Q000235:genetics; D013572:Synaptic Vesicles / Q000235:genetics / Q000502:physiology*; D014316:Tritium / Q000378:metabolism; D050495:Vesicular Inhibitory Amino Acid Transport Proteins / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D007527:Isoenzymes; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; C492244:Viaat protein, mouse; D014316:Tritium; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2