Regulated delivery of AMPA receptor subunits to the presynaptic membrane.
In recent years, a role for AMPA receptors as modulators of presynaptic functions has emerged. We have investigated the presence of AMPA receptor subunits and the possible dynamic control of their surface exposure at the presynaptic membrane. We demonstrate that the AMPA receptor subunits GluR1 and GluR2 are expressed and organized in functional receptors in axonal growth cones of hippocampal neurons. AMPA receptors are actively internalized upon activation and recruited to the surface upon depolarization. Pretreatment of cultures with botulinum toxin E or tetanus toxin prevents the receptor insertion into the plasma membrane, whereas treatment with alpha-latrotoxin enhances the surface exposure of GluR2, both in growth cones of cultured neurons and in brain synaptosomes. Purification of small synaptic vesicles through controlled-pore glass chromatography, revealed that both GluR2 and GluR1, but not the GluR2 interacting protein GRIP, copurify with synaptic vesicles. These data indicate that, at steady state, a major pool of AMPA receptor subunits reside in synaptic vesicle membranes and can be recruited to the presynaptic membrane as functional receptors in response to depolarization.
Schenk
Ursula
U
CNR Institute of Neuroscience, Cellular and Molecular Pharmacology, Center of Excellence for Neurodegenerative Diseases, Department of Medical Pharmacology, via Vanvitelli 32, 20129 Milano, Italy.
Verderio
Claudia
C
Benfenati
Fabio
F
Matteoli
Michela
M
D000818:Animals; D000906:Antibodies / Q000378:metabolism; D001905:Botulinum Toxins / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002458:Cell Fractionation; D002478:Cells, Cultured; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism; D020439:Growth Cones / Q000187:drug effects / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport; D050683:R-SNARE Proteins; D051381:Rats; D018091:Receptors, AMPA / Q000378:metabolism*; D013111:Spider Venoms / Q000494:pharmacology; D013570:Synaptic Membranes / Q000378:metabolism*; D013572:Synaptic Vesicles / Q000737:chemistry / Q000378:metabolism; D013744:Tetanus Toxin / Q000494:pharmacology; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D000906:Antibodies; D001905:Botulinum Toxins; D002118:Calcium; D018690:Excitatory Amino Acid Agonists; D005456:Fluorescent Dyes; D008565:Membrane Proteins; D021122:Protein Subunits; D050683:R-SNARE Proteins; D018091:Receptors, AMPA; D013111:Spider Venoms; D013744:Tetanus Toxin; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C020763:alpha-latrotoxin; C104722:glutamate receptor ionotropic, AMPA 2; C096326:botulinum toxin type E