Loss of glial fibrillary acidic protein results in decreased glutamate transport and inhibition of PKA-induced EAAT2 cell surface trafficking.
Loss of the astrocyte-specific intermediate filament protein, glial fibrillary acidic protein (GFAP) results in an increased susceptibility to ischemic insult, enhanced hippocampal LTP, and decreased cerebellar long-term depression (LTD). Because glutamate receptor activation plays a key role in cell death and cellular plasticity responses, we wanted to determine if alterations in glial glutamate transport could contribute to the GFAP null phenotype. To address functional changes in glutamate transport, we measured glutamate uptake in cortical, cerebellar, and hippocampal synaptosomal preparations from age-matched adult wild type and GFAP null mice and demonstrated a 25-30% reduction in the V(max) for d-aspartate uptake in the cortex and hippocampus of GFAP null animals. Western blot analysis of cortical synaptosomal fractions from wild type and GFAP null animals demonstrated that loss of GFAP results in decreases in both astrocytic (EAAT1) and neuronal (EAAT3) glutamate transporter subtypes. Immunohistochemical analysis demonstrated a region-specific modification of neuronal glutamate transporter, EAAT3 trafficking in the GFAP null phenotype. Analysis of primary cortical astrocyte cultures prepared from GFAP null and wild type mice demonstrated that loss of GFAP results in an inability to traffic the glial glutamate transporter, EAAT2, to the surface of the cell following protein kinase A (PKA) stimulation by dibutyryl cAMP. Taken together, these results suggest that the intermediate filament protein, GFAP plays a key role in modulating astrocytic and neuronal glutamate transporter trafficking and function.
Hughes
Ethan G
EG
Department of Pharmacology, Neuroscience Program, The George Washington University, Ross Hall Rm 656, 2300 Eye St., NW, Washington, DC 20037, USA.
Maguire
Jamie L
JL
McMinn
Melanie T
MT
Scholz
Rachael E
RE
Sutherland
Margaret L
ML
D027322:Amino Acid Transport System X-AG / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D003994:Bucladesine / Q000494:pharmacology; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology*; D027341:Excitatory Amino Acid Transporter 1 / Q000378:metabolism; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism*; D050580:Excitatory Amino Acid Transporter 3; D005904:Glial Fibrillary Acidic Protein / Q000172:deficiency / Q000235:genetics*; D050491:Glutamate Plasma Membrane Transport Proteins; D018698:Glutamic Acid / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000378:metabolism; D010641:Phenotype; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D027981:Symporters / Q000378:metabolism; D013574:Synaptosomes
D027322:Amino Acid Transport System X-AG; D027341:Excitatory Amino Acid Transporter 1; D027342:Excitatory Amino Acid Transporter 2; D050580:Excitatory Amino Acid Transporter 3; D005904:Glial Fibrillary Acidic Protein; D050491:Glutamate Plasma Membrane Transport Proteins; C493399:Slc1a1 protein, mouse; C493396:Slc1a2 protein, mouse; C493393:Slc1a3 protein, mouse; D027981:Symporters; D018698:Glutamic Acid; D003994:Bucladesine; D017868:Cyclic AMP-Dependent Protein Kinases