N-methyI-D-aspartate receptors （NMDARs） containing different GluN2 subunits play distinct roles in synaptic plasticity. Such differences may not only be determined by the channel properties, but also by differential surface distribution and synaptic localization. In the present study, using a Cy3-conjugated Fab fragment of the GFP antibody to label surface-located GluN2 subunits tagged with GFP at the N-terminus, we observed the membrane distribution patterns of GluN2A- or GluN2B-containing NMDARs in cultured rat hippocampal neurons. We found that surface NMDARs containing GluN2A, but not those containing GluN2B, were inclined to cluster at DIV7. Swapping the carboxyl termini of the GluN2 subunits completely reversed these distribution patterns. In addition, surface NMDARs containing GluN2A were preferentially associated with PSD-95. Taken together, the results of our study suggest that the clustering distribution of GluN2A- containing NMDARs is determined by the GluN2A C-terminus, and its interaction with PSD-95 plays an important role in this process.
Ying-Gang YanJie ZhangShu-Jun XuJian-Hong LuoShuang QiuWei Wang
Accumulating evidence indicates that the synaptic activation of N-methyl-o-aspartate receptors （NMDARs） has a neuroprotective effect on neurons. Our previous study demonstrated that APPL1 （adaptor protein containing pleckstrin homology domain, phosphotyrosine- binding domain, and leucine zipper motif） mediates the synaptic activity-dependent activation of PI3K-Akt signaling via coupling this pathway with NMDAR-PSD95 （postsynaptic density protein 95） complexes. However, the molecular mechanism underlying this process is still unknown. In the present study, we investigated the inter- action of APPL1 with PSD95 using co-immunocyto- chemical staining and western blotting. We found that the PDZ2 domain of PSD95 is a binding partner of APPL1. Furthermore, we identified serine 707 of APPL1, a pre- dicted phosphorylation site within the PDZ-binding motif at the C-terminus, as critical for the binding of APPL1 to PSD95, as well as for activation of the Akt signaling pathway during synaptic activity. This suggests that serine 707 of APPL1 is a potential phosphorylation site and may be involved in regulating the neuroprotective Akt signaling pathway that depends on synaptic NMDAR activity.
Jiejie WangWen LuLin ChenPing ZhangTingting QianWei CaoJianhong Luo
Abnormal approach-avoidance behavior has been linked to deficits in the mesolimbic dopamine（DA）system of the brain. Recently, increasing evidence has indicated that toll-like receptor 4（TLR4）, an important pattern-recognition receptor in the innate immune system,can be directly activated by substances of abuse, resulting in an increase of the extracellular DA level in the nucleus accumbens. We thus hypothesized that TLR4-dependent signaling might regulate approach-avoidance behavior. To test this hypothesis, we compared the novelty-seeking and social interaction behaviors of TLR4-deficient（TLR4^（-/-））and wild-type（WT） mice in an approach-avoidance conflict situation in which the positive motivation to explore a novel object or interact with an unfamiliar mouse was counteracted by the negative motivation to hide in exposed,large spaces. We found that TLR4^（-/-）mice exhibitedreduced novelty-seeking and social interaction in the large open spaces. In less stressful test apparatuses similar in size to the mouse cage, however, TLR4^（-/-）mice performed normally in both novelty-seeking and social interaction tests. The reduced exploratory behaviors under approachavoidance conflict were not due to a high anxiety level or an enhanced fear response in the TLR4^（-/-）mice, as these mice showed normal anxiety and fear responses in the open field and passive avoidance tests, respectively. Importantly,the novelty-seeking behavior in the large open field induced a higher level of c-Fos activation in the nucleus accumbens shell（NAc Sh） in TLR4^（-/-）mice than in WT mice. Partially inactivating the NAc Sh via infusion of GABA receptor agonists restored the novelty-seeking behavior of TLR4^（-/-）mice. These data suggested that TLR4 is crucial for positive motivational behavior under approach-avoidance conflict. TLR4-dependent activation of neurons in the NAc Sh may contribute to this phenomenon.
OBJECTIVE Temporal lobe epilepsy(TLE)is one of the most common types of human epilepsy,and they are often resistant to current treatments.METHODS By using optogenetic,electrophysiological,imaging and pharmacology strategies,we aimed toinvestigate the underlying circuit mechanism of TLE and tried to developthe novel and efficient approach to control epilepsy.RESULTS(1)Using micro PET and multichannel EEG recording,we found an abnormal neural network,characterized by early hypometabolism and after discharge spread,during the epileptogenensis of TLE.(2)Deep brain stimulation,especially low frequency stimulation,targeted the epileptic focus and the areas outside of the focus(critical regions for seizure spread),such as the piriform cortex,cerebellum,entorhinal cortex or subiculum,reduced seizure severity in TLE.Its anti-epileptic effect is time-window dependent and polarity dependent,which shows a promising strategy for treating epileptic seizures.(3)Using an optogenetic strategy,we demonstrated that excitatory projection from entorhinal cortex to hippocampus instructs the brain-stimulation treatments of epilepsy.(4)Our data from both the clinical and experimental studies further demonstrated that a disinhibitory GABAergic neuronmediated microcircuit in the subiculum contributes to secondary generalized seizures in TLE.(5)Finally,based on abnormal synchronization of the electrical activity in epileptic circuit,we developed electroresponsive hydrogel nanoparticles modified with angiopep-2 to facilitate the delivery of the antiepileptic drug phenytoin sodium,which greatly improves the therapeutic index.CONCLUSION Our findings may update the current view of epileptic neuronal networks and suggest possible promising ways for epilepsy treatment.
WANG YiYING Xiao-yingCHEN BinXU Ceng-linCHEN Zhong
