BENDER CRHISTIAN LUIS
Congresos y reuniones científicas
Título:
Post-synaptic activity drives CPEB3 expression: a cell-autonomous regulator of synaptic AMPA receptor phenotype. International Society of Neuroscience
Autor/es:
BENDER C; SUN L; LIU S
Lugar:
SAN DIEGO
Reunión:
Congreso; Annual Meeting of Society for Neuroscience; 2013
Resumen:
Many neurons in the brain fire action potentials in the absence of synaptic inputs. This intrinsic pacemaking activity together with excitatory and inhibitory synaptic inputs controls the output of neuronal circuits. However whether such somatic spiking activity regulates the expression of post-synaptic receptors in a cell-autonomous manner is not known. Here we tested the hypothesis that the intrinsic activity of cerebellar interneurons post-synaptically drives the expression of GluR2-lacking synaptic AMPA receptors (AMPARs), which are calcium permeable, have large conductance and show rapid kinetics.
To test this idea, we incubated cerebellar slices in TTX (tetrodotoxin) in the presence of GABAR and glutamate receptor blockers for 3 hours and then measured spontaneous EPSCs from stellate cells using the whole cell patch clamp technique. Synaptic AMPAR phenotype was assessed from the I-V relationship of the EPSCs when spermine was included in the pipette solution. We found that blocking the somatic action potentials changed the I-V relationship of the EPSCs from inwardly rectifying to nearly linear, indicating an increase in synaptic GluR2-containing receptors in stellate cells. When TTX was co-incubated with a protein synthesis inhibitor it no longer produced the increase in GluR2-containing AMPARs.
CPEB3 is a RNA-binding protein that binds to GluR2 mRNA and suppresses GluR2 synthesis. We tested the hypothesis that blocking action potential firing reduces the CPEB3 expression and thereby elevates synaptic GluR2 receptors. We incubated cultured cerebellar neurons (18-21 days in vitro) with TTX for 3 hours and found that CPEB3-immunoreactivity decreased in stellate cells. We next examined the idea that somatic action potentials activate conventional PKC, which elevates CPEB3 levels. Indeed, application of TTX reduced PKC activity in stellate cells and this was reversed by the addition of a PKC activator, PMA. Furthermore PKC inhibitors lowered CPEB3 levels in stellate cells, mimicking the effects of TTX treatment, and the TTX-induced decrease in CPEB3-ir was reversed by co-application of PMA.
Our results suggest that somatic action potentials activate PKC and increase the abundance of CPEB3 in stellate cells. This suppresses the synthesis of GluR2, and leads to the expression of GluR2-lacking AMPARs at synapses. Our findings reveal an important cell-autonomous role for the spontaneous activity of inhibitory interneurons in determining the synaptic AMPAR phenotype
To test this idea, we incubated cerebellar slices in TTX (tetrodotoxin) in the presence of GABAR and glutamate receptor blockers for 3 hours and then measured spontaneous EPSCs from stellate cells using the whole cell patch clamp technique. Synaptic AMPAR phenotype was assessed from the I-V relationship of the EPSCs when spermine was included in the pipette solution. We found that blocking the somatic action potentials changed the I-V relationship of the EPSCs from inwardly rectifying to nearly linear, indicating an increase in synaptic GluR2-containing receptors in stellate cells. When TTX was co-incubated with a protein synthesis inhibitor it no longer produced the increase in GluR2-containing AMPARs.
CPEB3 is a RNA-binding protein that binds to GluR2 mRNA and suppresses GluR2 synthesis. We tested the hypothesis that blocking action potential firing reduces the CPEB3 expression and thereby elevates synaptic GluR2 receptors. We incubated cultured cerebellar neurons (18-21 days in vitro) with TTX for 3 hours and found that CPEB3-immunoreactivity decreased in stellate cells. We next examined the idea that somatic action potentials activate conventional PKC, which elevates CPEB3 levels. Indeed, application of TTX reduced PKC activity in stellate cells and this was reversed by the addition of a PKC activator, PMA. Furthermore PKC inhibitors lowered CPEB3 levels in stellate cells, mimicking the effects of TTX treatment, and the TTX-induced decrease in CPEB3-ir was reversed by co-application of PMA.
Our results suggest that somatic action potentials activate PKC and increase the abundance of CPEB3 in stellate cells. This suppresses the synthesis of GluR2, and leads to the expression of GluR2-lacking AMPARs at synapses. Our findings reveal an important cell-autonomous role for the spontaneous activity of inhibitory interneurons in determining the synaptic AMPAR phenotype
