Antagonistic effects of TrkB and p75(NTR) on NMDA receptor currents in post-synaptic densities transplanted into Xenopus oocytes

作者：Sandoval Mauricio; Sandoval Rodrigo; Thomas Ulrich; Spilker Christina; Smalla Karl Heinz; Falcon Romina; Marengo Juan Jose; Calderon Rodrigo; Saavedra Veronica; Heumann Rolf; Bronfman Francisca; Garner Craig C; Gundelfinger Eckart D; Wyneken Ursula^*

来源：Journal of Neurochemistry, 2007, 101(6): 1672-1684.

DOI：10.1111/j.1471-4159.2007.04519.x

• brain-derived neurotrophic factor
• neurotrophins
• NMDA receptor
• post-synaptic density
• synapse

Brain-derived neurotrophic factor (BDNF) and its receptor TrkB are essential regulators of synaptic function in the adult CNS. A TrkB-mediated effect at excitatory synapses is enhancement of NMDA receptor (NMDA-R)-mediated currents. Recently, opposing effects of TrkB and the pan-neurotrophin receptor p75(NTR) on long-term synaptic depression and long-term potentiation have been reported in the hippocampus. To further study the regulation of NMDA-Rs by neurotrophin receptors in their native protein environment, we micro-transplanted rat forebrain post-synaptic densities (PSDs) into Xenopus oocytes. One-minute incubations of oocytes with BDNF led to dual effects on NMDA-R currents: either TrkB-dependent potentiation or TrkB-independent inhibition were observed. Pro-nerve growth factor, a ligand for p75(NTR) but not for TrkB, produced a reversible, dose-dependent, TrkB-independent and p75(NTR)-dependent inhibition of NMDA-Rs. Fractionation experiments showed that p75(NTR) is highly enriched in the PSD protein fraction. Immunoprecipitation and pull-down experiments further revealed that p75(NTR) is a core component of the PSD, where it interacts with the PDZ3 domain of the scaffolding protein SAP90/PSD-95. Our data provide striking evidence for a rapid inhibitory effect of p75(NTR) on NMDA-R currents that antagonizes TrkB-mediated NMDA-R potentiation. These opposing mechanisms might be present in a large proportion of forebrain synapses and may contribute importantly to synaptic plasticity.

• 出版日期2007-6