RESUMO
Experiments were conducted in both HEK cells and cerebellar neurons to investigate whether CXC chemokine receptor 2 (CXCR2) is functionally coupled to GluR1. The co-expression of CXCR2 with GluR1 in HEK cells increased (i) the GluR1 "apparent" affinity for the transmitter; (ii) the GluR1 channel open probability; and (iii) GluR1 binding site cooperativity upon CXCR2 stimulation with CXC chemokine ligand 2 (CXCL2). The affinity of C-terminal-deleted GluR1 for glutamate (Glu) remained stable instead. Furthermore, CXCL2 increased the binding site cooperativity of AMPA receptors in rat cerebellar granule cells; and the amplitude of spontaneous excitatory postsynaptic current (sEPSCs) in Purkinje neurons (PNs). Our findings indicate that the coupling of CXCR2 with GluR1 may modulate glutamatergic synaptic transmission.
Assuntos
Sistema Nervoso Central/metabolismo , Quimiocinas CXC/metabolismo , Ácido Glutâmico/metabolismo , Receptores de AMPA/metabolismo , Receptores de Interleucina-8B/metabolismo , Sinapses/metabolismo , Transmissão Sináptica/imunologia , Animais , Sítios de Ligação/efeitos dos fármacos , Sítios de Ligação/imunologia , Células Cultivadas , Sistema Nervoso Central/imunologia , Córtex Cerebelar/efeitos dos fármacos , Córtex Cerebelar/imunologia , Córtex Cerebelar/metabolismo , Quimiocinas CXC/imunologia , Quimiocinas CXC/farmacologia , DNA Complementar/genética , Relação Dose-Resposta a Droga , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/imunologia , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/imunologia , Ácido Glutâmico/farmacologia , Humanos , Canais Iônicos/genética , Canais Iônicos/imunologia , Neurônios/efeitos dos fármacos , Neurônios/imunologia , Neurônios/metabolismo , Ratos , Ratos Sprague-Dawley , Ratos Wistar , Receptores de AMPA/genética , Receptores de AMPA/imunologia , Receptores de Interleucina-8B/genética , Receptores de Interleucina-8B/imunologia , Sinapses/imunologiaRESUMO
Cultured cerebellar granule neurons are widely used as a cellular model to study mechanisms of neuronal cell death because they undergo programmed cell death when switched from a culture medium containing 25 mM to one containing 5 mM K(+). We have found that the growth-related gene product beta (GRObeta) partially prevents the K(+)-depletion-induced cell death, and that the neuroprotective action of GRObeta on granule cells is mediated through the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) type of ionotropic glutamate receptors. GRObeta-induced survival was suppressed by 6-cyano-7-nitroquinoxaline-2,3-dione, which is a specific antagonist of AMPA/kainate receptors; it was not affected by the inhibitor of N-methyl-D-aspartate receptors, 2-amino-5-phosphonopentanoic acid, and was comparable to the survival of granule cells induced by AMPA (10 microM) treatment. Moreover, GRObeta-induced neuroprotection was abolished when granule cells were treated with antisense oligonucleotides specific for the AMPA receptor subunits, which significantly reduced receptor expression, as verified by Western blot analysis with subunit-specific antibodies and by granule cell electrophysiological sensitivity to AMPA. Our data demonstrate that GRObeta is neurotrophic for cerebellar granule cells, and that this activity depends on AMPA receptors.