Neuronal exosomal miRNA-dependent translational regulation of astroglial glutamate transporter GLT1.
Perisynaptic astrocytes express important glutamate transporters, especially excitatory amino acid transporter 2 (EAAT2, rodent analog GLT1) to regulate extracellular glutamate levels and modulate synaptic activation. In this study, we investigated an exciting new pathway, the exosome-mediated transfer of microRNA (in particular, miR-124a), in neuron-to-astrocyte signaling. Exosomes isolated from neuron-conditioned medium contain abundant microRNAs and small RNAs. These exosomes can be directly internalized into astrocytes and increase astrocyte miR-124a and GLT1 protein levels. Direct miR-124a transfection also significantly and selectively increases protein (but not mRNA) expression levels of GLT1 in cultured astrocytes. Consistent with our in vitro findings, intrastriatal injection of specific antisense against miR-124a into adult mice dramatically reduces GLT1 protein expression and glutamate uptake levels in striatum without reducing GLT1 mRNA levels. MiR-124a-mediated regulation of GLT1 expression appears to be indirect and is not mediated by its suppression of the putative GLT1 inhibitory ligand ephrinA3. Moreover, miR-124a is selectively reduced in the spinal cord tissue of end-stage SOD1 G93A mice, the mouse model of ALS. Subsequent exogenous delivery of miR-124a in vivo through stereotaxic injection significantly prevents further pathological loss of GLT1 proteins, as determined by GLT1 immunoreactivity in SOD1 G93A mice. Together, our study characterized a new neuron-to-astrocyte communication pathway and identified miRNAs that modulate GLT1 protein expression in astrocytes in vitro and in vivo.
Department of Neuroscience, Tufts University, Boston, Massachusetts 02111, USA.
Lydie
L
Morel
Melissa
M
Regan
Haruki
H
Higashimori
Seng Kah
SK
Ng
Christine
C
Esau
Svetlana
S
Vidensky
Jeffrey
J
Rothstein
Yongjie
Y
Yang
D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D002478:Cells, Cultured; D003342:Corpus Striatum / Q000166:cytology / Q000378:metabolism; D004705:Endocytosis; D027342:Excitatory Amino Acid Transporter 2 / Q000235:genetics* / Q000378:metabolism; D055354:Exosomes / Q000378:metabolism* / Q000648:ultrastructure; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D005971:Glutamates / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D035683:MicroRNAs / Q000235:genetics*; D008854:Microscopy, Electron; D009474:Neurons / Q000378:metabolism*; D014176:Protein Biosynthesis; D015398:Signal Transduction / Q000235:genetics; D013116:Spinal Cord / Q000378:metabolism / Q000473:pathology; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism
D027342:Excitatory Amino Acid Transporter 2; D005971:Glutamates; D035683:MicroRNAs; C540079:Mirn124 microRNA, mouse; C493396:Slc1a2 protein, mouse; C109415:SOD1 G93A protein; D013482:Superoxide Dismutase