The amino terminus of the glial glutamate transporter GLT-1 interacts with the LIM protein Ajuba.
We have identified a cytoplasmic LIM protein, Ajuba, which interacts with the amino terminus of GLT-1, the most abundant plasma membrane glutamate transporter in the brain. Ajuba has a cytoplasmic location when expressed alone in COS cells, but translocates to colocalize with GLT-1 at the plasma membrane when GLT-1 is coexpressed. Ajuba is expressed in cerebellum, cortex, hippocampus, and retina and also in organs outside the CNS. Ajuba is found with GLT-1 in astrocytes, cerebellar Bergmann glia and retinal neurons, and antibodies to Ajuba coimmunoprecipitate GLT-1 from brain. For GLT-1 expressed in COS cells, coexpression of Ajuba did not affect the transporter's K(m) or V(max) for glutamate. Since Ajuba is known to activate MAP kinase enzymes, and its homologue Zyxin binds to cytoskeletal proteins, we propose that Ajuba is a scaffolding protein allowing GLT-1 to regulate intracellular signaling or interact with the cytoskeleton.
Marie
Hélène
H
Department of Physiology, Laboratory of Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom.
Billups
Daniela
D
Bedford
Fiona K
FK
Dumoulin
Andrea
A
Goyal
Rakesh K
RK
Longmore
Gregory D
GD
Moss
Stephen J
SJ
Attwell
David
D
D000375:Aging / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism*; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism; D003001:Cloning, Molecular; D003599:Cytoskeleton / Q000378:metabolism*; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism*; D007150:Immunohistochemistry; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D060588:LIM Domain Proteins; D008969:Molecular Sequence Data; D009457:Neuroglia / Q000166:cytology / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D012160:Retina / Q000166:cytology / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques; D014781:Viscera / Q000378:metabolism
C119385:Ajuba protein, rat; D027342:Excitatory Amino Acid Transporter 2; D018398:Homeodomain Proteins; D007473:Ion Channels; D060588:LIM Domain Proteins; D018698:Glutamic Acid