Enhancement of AMPA currents and GluR1 membrane expression through PKA‐coupled adenosine A_2A receptors

Abstract

Phosphorylation of glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors by Protein Kinase A (PKA) is known to regulate AMPA receptor (AMPAR) trafficking and stabilization at the postsynaptic membrane, which in turn is one of the key mechanisms by which synaptic transmission and plasticity are tuned. However, not much is known as to how Gs-coupled receptors contribute to endogenous PKA-mediated regulation of AMPA receptor function. Here we report that activation of the excitatory A(2A) adenosine receptor by 2-[4-(2-p-carboxyethyl)phenylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680, 1-30 nM) facilitates AMPA-evoked currents in CA1 pyramidal neurons, by a mechanism dependent on PKA activation, but not on protein synthesis. This modulation of AMPA currents was mimicked by forskolin (1 μM) and did not occur in stratum radiatum interneurons. Superfusion of the A(2A) receptor agonist also caused an increase in the amplitude of miniature excitatory postsynaptic currents (mEPSCs), as well as in the membrane levels of GluR1 subunits phosphorylated at the PKA site (Ser845). The impact of this increase on GluR1-containing AMPA receptor expression was evidenced by the potentiation of LTP at the CA3-CA1 synapse that followed brief activation of A(2A) receptors. We thus propose that in conditions of increased adenosine availability, A(2A) receptor activation is responsible for setting part of the endogenous GluR1 Ser-845 phosphorylation tonus and hence, the availability of the GluR1-containing AMPA receptor extrasynaptic pool for synaptic insertion and reinforcement of synaptic strength.

Extracellular Alpha-Synuclein Oligomers Modulate Synaptic Transmission and Impair LTP Via NMDA-Receptor Activation

“…For AMPA and NMDA current-voltage relationship a different intracellular solution was used [125 mM CsCl, 8 mM NaCl, 1 mM CaCl 2 , 10 mM EGTA, 10 mM HEPES, 10 mM D-glucose, 5 mM MgATP, and 0.4 mM NaGTP, pH 7.2, adjusted with CsOH (50 wt% in water), 280 -290 mOsm; 0.1 mM spermine was added for EPSC AMPA recordings]. Mixed NMDA/AMPA EPSCs were recorded from CA1 pyramidal cells upon stimulation of the Schaffer collateral fibers (0.2 ms rectangular pulses delivered each 15 s), in the presence of glycine (50 M) and picrotoxin (50 M), as described previously (Dias et al, 2012). Whole-cell recordings were performed at room temperature in voltage-clamp mode (V h ϭ Ϫ80 mV, after liquid junction potential correction) with either an EPC-7 (List Biologic) or an Axopatch 200B (Molecular Devices) amplifier, under the control of pClamp10 software (Molecular Devices).…”

“…Fresh slices were submitted to a biotinylation technique as described previously (Dias et al, 2012) to isolate the membrane fraction from the total fraction. Slices were washed three times with ice-cold PBS/Ca 2ϩ /Mg 2ϩ washing buffer (137 mM NaCl, 2.7 mM KCl, 4.3 mM NaH 2 PO 4 , 1 mM CaCl 2 , and 0.5 mM MgCl 2 ) and then incubated with 1 mg ⅐ ml Ϫ1 of EZ-Link Sulfo-NHS-LC-biotin (Sigma) resuspended in a tetraethylammonium (TEA) buffer (10 mM TEA, 2 mM CaCl 2 , and 150 mM NaCl), for 60 min at 4°C using gentle rotation.…”

Modulation of excitatory neurotransmission by neuronal/glial signalling molecules: interplay between purinergic and glutamatergic systems

“…A2A receptors regulate plasticity in the hippocampus by their co-localization and synergistic action with metabotropic glutamate receptors facilitating NMDA-mediated currents [244,245]. Moreover, the ability of A2A receptors to enhance the activity-dependent efficiency of excitatory synapses has been argued to result from a number of additional mechanisms, such as (i) enhanced release of neurotransmitters [291], (ii) facilitation of brain-derived neurotropic factor-induced signalling [292,293], (iii) enhanced responsiveness of NMDA receptors to transmitter glutamate [294,295] and (iv) increased availability of GluR1-containing AMPA receptors for synaptic insertion [296].…”

Lipid rafts, synaptic transmission and plasticity: Impact in age-related neurodegenerative diseases

“…Upon ageing there is an increased influence of adenosine A 2A receptors upon synaptic transmission and plasticity . Adenosine A 2A receptors have long lasting facilitatory influences upon synaptic plasticity (Dias et al, 2012) and as mentioned above, A 2A receptors trigger translocation of TrkB receptors to lipid rafts (Assaife-Lopes et al, 2010). Thus, upon ageing adaptative as well as compensatory changes in signaling of key proteins for proper synaptic function do occur and some of those changes might also involve their intimate relationship to their lipid environment.…”