Alexander disease mutant glial fibrillary acidic protein compromises glutamate transport in astrocytes.
Alexander disease (AxD) is a leukodystrophy caused by heterozygous mutations in the gene for glial fibrillary acidic protein, an intermediate filament protein expressed by astrocytes. The mutation causes prominent protein aggregates inside astrocytes; there is also loss of myelin and oligodendrocytes and neuronal degeneration. We show that immunohistochemical staining for glutamate transporter 1, the major brain glutamate transporter expressed primarily in astrocytes suggests decreased levels in the hippocampi of infantile AxD patients. A knock-in mouse model of AxD also shows significant reduction of glutamate transporter 1 in the hippocampus. To explore this phenomenon at the cellular level, wild-type and R239C mutant glial fibrillary acidic proteins (the most common mutation) were overexpressed in astrocytes in culture. Western blotting and whole-cell patch clamp recordings demonstrated that the R239C astrocytes exhibited markedly reduced glutamate transporter 1 protein levels; this resulted in attenuated or abolished glutamate-induced inward transporter current. Neurons cocultured with the R239C astrocytes exhibited increased death after glutamate challenge. These results indicate that aberrant astrocytes have decreased glutamate uptake, which may play an important role in the pathogenesis of neuronal and oligodendrocyte injury and death in AxD.
Tian
Rujin
R
Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032, USA.
Wu
Xiaoping
X
Hagemann
Tracy L
TL
Sosunov
Alexandre A
AA
Messing
Albee
A
McKhann
Guy M
GM
Goldman
James E
JE
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D038261:Alexander Disease / Q000235:genetics* / Q000473:pathology*; D000818:Animals; D001120:Arginine / Q000235:genetics; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D018920:Coculture Techniques / Q000379:methods; D003545:Cysteine / Q000235:genetics; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism*; D005434:Flow Cytometry / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology; D007608:Kainic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D009154:Mutation / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D051381:Rats; D014162:Transfection / Q000379:methods
D018690:Excitatory Amino Acid Agonists; D027342:Excitatory Amino Acid Transporter 2; D005904:Glial Fibrillary Acidic Protein; D009419:Nerve Tissue Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D015124:8-Bromo Cyclic Adenosine Monophosphate; C020889:dihydrokainic acid; D001120:Arginine; D003545:Cysteine; D007608:Kainic Acid
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