title: Hippocampal AMPA autoreceptors positively coupled to NMDA autoreceptors traffic in a constitutive manner and undergo adaptative changes following enriched environment training.
abstract: α-Amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) autoreceptors exist on glutamate hippocampal terminals. Aimed at investigating whether these autoreceptors traffic constitutively, (S)AMPA-evoked [(3)H]D-ASP release from synaptosomes enriched with peptides that impede the interaction of GluA2 subunits with cytosolic proteins involved in receptor movements [namely Glutamate Receptor-Interacting Protein (GRIP), Protein Interacting with C kinase 1 (PICK1), N-ethyl-maleimide-Sensitive Fusion protein NSF proteins] was monitored. (S)AMPA alone had no effect on the spontaneous release of [(3)H]D-ASP from control synaptosomes, but became efficacious in the presence of cyclothiazide or when preventing GluA2/GRIP/PICK1, but not GluA2/NSF, interaction. Hippocampal glutamatergic terminals also possess NMDA autoreceptors. 10 μM NMDA/1 μM glycine-induced [(3)H]D-ASP release was concentration-dependently increased by (S)AMPA. Cyclothiazide potentiated the 10 μM NMDA/1 μM glycine/50 μM (S)AMPA-induced [(3)H]D-ASP overflow, while NBQX halved and MK-801 abolished it, suggesting NMDA-AMPA autoreceptor cross-talk. Western Blot analysis of sub-synaptic fractions confirmed presynaptic GluN2B-GluA2/3 co-localization. Impeding GluA2/GRIP/PICK1 interaction facilitated the NMDA/glycine/(S)AMPA-induced release of [(3)H]D-ASP, while competing for GluA2/NSF interaction reduced it, indicating that NMDA receptor favours AMPA receptor insertion in synaptosomal plasmamembranes. Finally, rearing mice in enriched environment unveiled the (S)AMPA-induced release of [(3)H]D-ASP, but leaved unmodified that caused by NMDA/glycine. The NBQX-sensitive, 50 μM (S)AMPA-evoked release of [(3)H]D-ASP was insensitive to cyclothiazide and to peptide interfering with GluA2/GRIP/PICK1 interaction but was addictive to that caused by NMDA/glycine. Presynaptic GluA2/3 immunoreactivity in EE hippocampal terminals was increased, while GluN2B was unchanged. We conclude that hippocampal AMPA autoreceptors positively coupled to NMDA autoreceptors traffic in a constitutive manner and undergo functional up-regulation in EE animals.
authors.affiliation: Department of Experimental Medicine, Pharmacology and Toxicology Section, University of Genoa, 16148 Genoa, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Summa
authors.forename: Silvia
authors.initials: S
authors.lastname: Di Prisco
authors.forename: Massimo
authors.initials: M
authors.lastname: Grilli
authors.forename: Mario
authors.initials: M
authors.lastname: Marchi
authors.forename: Anna
authors.initials: A
authors.lastname: Pittaluga
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D001581:Benzothiadiazines / Q000494:pharmacology; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D026603:D-Aspartic Acid / Q000187:drug effects / Q000378:metabolism; D000076122:Disks Large Homolog 4 Protein; D004305:Dose-Response Relationship, Drug; D004777:Environment; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D051528:Guanylate Kinases / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D047468:Immunoprecipitation; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D052066:N-Ethylmaleimide-Sensitive Proteins / Q000378:metabolism; D016202:N-Methylaspartate / Q000494:pharmacology; D009687:Nuclear Proteins; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D016708:Synaptophysin / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D014316:Tritium / Q000378:metabolism / Q000493:pharmacokinetics; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
chemical_list: D001581:Benzothiadiazines; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D000076122:Disks Large Homolog 4 Protein; C501447:Dlg4 protein, mouse; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D008565:Membrane Proteins; D009687:Nuclear Proteins; C498298:PICK1 protein, rat; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D016708:Synaptophysin; D014316:Tritium; D026603:D-Aspartic Acid; D016202:N-Methylaspartate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D051528:Guanylate Kinases; D052066:N-Ethylmaleimide-Sensitive Proteins; C498737:Nsf protein, rat; C104722:glutamate receptor ionotropic, AMPA 2; C004639:cyclothiazide