title: Activation of adenosine A2A receptors induces TrkB translocation and increases BDNF-mediated phospho-TrkB localization in lipid rafts: implications for neuromodulation.
abstract: Brain-derived neurotrophic factor (BDNF) signaling is critical for neuronal development and transmission. Recruitment of TrkB receptors to lipid rafts has been shown to be necessary for the activation of specific signaling pathways and modulation of neurotransmitter release by BDNF. Since TrkB receptors are known to be modulated by adenosine A(2A) receptor activation, we hypothesized that activation of A(2A) receptors could influence TrkB receptor localization among different membrane microdomains. We found that adenosine A(2A) receptor agonists increased the levels of TrkB receptors in the lipid raft fraction of cortical membranes and potentiated BDNF-induced augmentation of phosphorylated TrkB levels in lipid rafts. Blockade of the clathrin-mediated endocytosis with monodansylcadaverine (100 microm) did not modify the effects of the A(2A) receptor agonists but significantly impaired BDNF effects on TrkB recruitment to lipid rafts. The effect of A(2A) receptor activation in TrkB localization was mimicked by 5 microm forskolin, an adenylyl cyclase activator. Also, it was blocked by the PKA inhibitors Rp-cAMPs and PKI-(14-22), and by the Src-family kinase inhibitor PP2. Moreover, removal of endogenous adenosine or disruption of lipid rafts reduced BDNF stimulatory effects on glutamate release from cortical synaptosomes. Lipid raft integrity was also required for the effects of BDNF on hippocampal long-term potentiation at CA1 synapses. Our data demonstrate, for the first time, a BDNF-independent recruitment of TrkB receptors to lipid rafts induced by activation of adenosine A(2A) receptors, with functional consequences for TrkB phosphorylation and BDNF-induced modulation of neurotransmitter release and hippocampal plasticity.
authors.affiliation: Institute of Pharmacology and Neuroscience, Faculty of Medicine, University of Lisbon, 1649-028 Lisbon, Portugal.
authors.forename: Natália
authors.initials: N
authors.lastname: Assaife-Lopes
authors.forename: Vasco C
authors.initials: VC
authors.lastname: Sousa
authors.forename: Daniela B
authors.initials: DB
authors.lastname: Pereira
authors.forename: Joaquim A
authors.initials: JA
authors.lastname: Ribeiro
authors.forename: Moses V
authors.initials: MV
authors.lastname: Chao
authors.forename: Ana M
authors.initials: AM
authors.lastname: Sebastião
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D002966:Clathrin / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D007150:Immunohistochemistry; D017774:Long-Term Potentiation / Q000187:drug effects; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010627:Phenethylamines / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D043705:Receptor, Adenosine A2A / Q000378:metabolism*; D020813:Receptor, trkB / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013569:Synapses / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects; D013574:Synaptosomes / Q000378:metabolism
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D002966:Clathrin; D010627:Phenethylamines; D043705:Receptor, Adenosine A2A; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D020813:Receptor, trkB; D017868:Cyclic AMP-Dependent Protein Kinases; D000241:Adenosine