title: Distinct roles of NR2A and NR2B cytoplasmic tails in long-term potentiation.
abstract: NMDA receptors (NMDARs) are critical mediators of activity-dependent synaptic plasticity, but the differential roles of NR2A- versus NR2B-containing NMDARs have been controversial. Here, we investigate the roles of NR2A and NR2B in long-term potentiation (LTP) in organotypic hippocampal slice cultures using RNA interference (RNAi) and overexpression, to complement pharmacological approaches. In young slices, when NR2B is the predominant subunit expressed, LTP is blocked by the NR2B-selective antagonist Ro25-6981 [R-(R,S)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenylmethyl)-1-piperidine propranol]. As slices mature and NR2A expression rises, activation of NR2B receptors became no longer necessary for LTP induction. LTP was blocked, however, by RNAi knockdown of NR2B, and this was rescued by coexpression of an RNAi-resistant NR2B (NR2B*) cDNA. Interestingly, a chimeric NR2B subunit in which the C-terminal cytoplasmic tail was replaced by that of NR2A failed to rescue LTP, whereas the reverse chimera, NR2A channel with NR2B tail, was able to restore LTP. Thus, expression of NR2B with its intact cytoplasmic tail is required for LTP induction, at an age when channel activity of NR2B-NMDARs is not required for LTP. Overexpression of wild-type NR2A failed to rescue LTP in neurons transfected with the NR2B-RNAi construct, despite restoring NMDA-EPSC amplitude to a similar level as NR2B*. Surprisingly, an NR2A construct lacking its entire C-terminal cytoplasmic tail regained its ability to restore LTP. Together, these data suggest that the NR2B subunit plays a critical role for LTP, presumably by recruiting relevant molecules important for LTP via its cytoplasmic tail. In contrast, NR2A is not essential for LTP, and its cytoplasmic tail seems to carry inhibitory factors for LTP.
authors.affiliation: Department of Basic Science, The Commonwealth Medical College, Scranton, Pennsylvania 18510, USA. kfoster@tcmedc.org
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Foster
authors.forename: Nathan
authors.initials: N
authors.lastname: McLaughlin
authors.forename: Dieter
authors.initials: D
authors.lastname: Edbauer
authors.forename: Marnie
authors.initials: M
authors.lastname: Phillips
authors.forename: Andrew
authors.initials: A
authors.lastname: Bolton
authors.forename: Martha
authors.initials: M
authors.lastname: Constantine-Paton
authors.forename: Morgan
authors.initials: M
authors.lastname: Sheng
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001703:Biophysics / Q000379:methods; D003593:Cytoplasm / Q000378:metabolism; D004558:Electric Stimulation / Q000379:methods; D018683:Excitatory Amino Acid Agents / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D016202:N-Methylaspartate / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
chemical_list: D018683:Excitatory Amino Acid Agents; C120997:NR2A NMDA receptor; C121001:NR2B NMDA receptor; D034741:RNA, Small Interfering; D016194:Receptors, N-Methyl-D-Aspartate; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D016202:N-Methylaspartate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid