Re-evaluation of GABA transport in neuronal and glial cell cultures: correlation of pharmacology and mRNA localization.
Molecular cloning has revealed the existence of four distinct transporters for the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), termed GAT-1, GAT-2, GAT-3, and BGT-1. To determine which of the cloned transporters are in neurons and which are in glia, we have undertaken a combined pharmacological and molecular biological study using cell cultures derived from rat brain. In neuronal cultures approximately 70% of GABA transport is sensitive to the GAT-1-selective ligand NNC-711 and drug potencies at this site correlate well with their potencies at GAT-1; GAT-1 mRNA is abundant in these cultures as determined by northern blot analysis. Drug potencies at the NNC-711-resistant component correlate well with their potencies at GAT-2 and GAT-3, whose pharmacological profiles are similar to one another. Northern blots reveal the presence of mRNA for GAT-3 in neuronal cultures, whereas GAT-2 and BGT-1 mRNAs are not detected. Type 1 astrocyte cultures exhibit very low levels of GABA transport activity, which has very low potency for GABA but high potency for taurine. Such cultures have mRNA for a taurine transporter and BGT-1, but not for GAT-1, GAT-2, and GAT-3. In cultures containing O-2A progenitor cells and Type 2 astrocytes, approximately 75% of GABA uptake is sensitive to NNC-711 and drug potencies at this site correlate well with their potencies at GAT-1; GAT-1 mRNA is abundant. Drug potencies at the NNC-711-resistant component correlate well with their potencies at GAT-2 and GAT-3; mRNAs for both of these transporters are present (though GAT-2 mRNA is the more abundant), as is BGT-1 mRNA. In summary, these data demonstrate heterogeneity of both neuronal and glial GABA transport.
Borden
L A
LA
Department of Pharmacology, Synaptic Pharmaceutical Corporation, Paramus, NJ 07652, USA.
Smith
K E
KE
Vaysse
P J
PJ
Gustafson
E L
EL
Weinshank
R L
RL
Branchek
T A
TA
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D001692:Biological Transport; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D002352:Carrier Proteins; D012333:RNA, Messenger; D005680:gamma-Aminobutyric Acid