doi: 10.1038/nn.2952.
PDZ binding of TARPγ-8 controls synaptic transmission but not synaptic plasticity
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- PMID:22002768
- PMCID: PMC3206644
- DOI: 10.1038/nn.2952
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PDZ binding of TARPγ-8 controls synaptic transmission but not synaptic plasticity
Akio Sumioka et al. Nat Neurosci..
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Abstract
The reduction in synaptic transmission and plasticity in mice lacking the hippocampus-enriched AMPA receptor (AMPAR) auxiliary subunit TARPγ-8 could be a result of a reduction in AMPAR expression or of the direct action of γ-8. We generated TARPγ-8Δ4 knock-in mice lacking the C-terminal PDZ ligand. We found that synaptic transmission and AMPARs were reduced in the mutant mice, but extrasynaptic AMPAR expression and long-term potentiation (LTP) were unaltered. Our findings suggest that there are distinct TARP-dependent mechanisms for synaptic transmission and LTP.
Figures
TARP©-8 PDZ binding is necessary for synaptic localization of AMPARs. (a) diagram of the synaptic AMPAR/TARP/PSD-95 complex. The PDZ ligand (–TTPV) is deleted. (b) The anti-©-8 antibody recognized ©-8 in bothγ-8+/+ andγ-8Δ4/Δ4, whereas anti-TTPV antibody recognized ©-8 only in WT. Brain lysates were immunoprecipitated with normal rabbit IgG (control) or anti ©-8 antibody, followed by western blotting. All full and uncropped blots are shown in Supplementary Figure 7. (c) PSD-95 is not associated with ©-8⊗4in vivo. PSD-95 was co-immunoprecipitated with ©-8 inγ-8+/+, but not inγ-8Δ4/Δ4 mice. (d) Protein levels of ©-8, GluA1, and GluA2/3 were somewhat decreased in hippocampi in a ©-8⊗4 gene dosage-dependent manner (n=4). (e, f) Protein levels of ©-8, GluA1, and GluA2/3 in the PSD fraction from hippocampus were reduced inγ-8Δ4/Δ4 mice, but not in the Triton X-100-solublized synaptosome fraction (Syn/Tx). In contrast, expression of ©-8, GluA1, and GluA2/3 in the Syn/Tx fraction was significantly reduced inγ-8−/− mice, but not inγ-8Δ4/Δ4 mice. (f) Protein levels were normalized to those fromγ-8+/+ mice (n=4). Synaptophysin (Sph) was used as a non-PSD protein. All data are given as mean ± s.e.m.; *P < 0.05.
The ©-8 PDZ ligand modulates AMPAR-mediated basal transmission, but not LTP.(a) Ratio of AMPAR- to NMDAR-EPSCs is reduced by ~30% in CA1 pyramidal cells fromγ-8Δ4/Δ4 slices (n=11) compared with those fromγ-8+/+ slices (n=5). Representative examples of averaged EPSCs (AMPAR current=light trace; NMDAR current=dark trace). Calibration: 100 ms, 20 pA (+/+) and 16 pA (⊗4/⊗4).(b) Ratio of stimulus intensity (input) to the EPSP slope (output). Input-output was significantly reduced in slices fromγ-8Δ4/Δ4 (n=6) compared to those fromγ-8+/+ mice (n=10). *P < 0.05 paired t-test.(c) 100 nM AMPA-evoked whole cell currents are reduced by ~38% inγ-8Δ4/Δ4 (n=8) compared toγ-8+/+ mice (n=7). Inset, AMPA-evoked current from representative cells are shown. Calibration: 1 min, 50 pA.(d) Extracellular recordings of field EPSPs before and after tetanic stimulation of Schaffer collaterals (arrow). LTP was elicited inγ-8+/+ (open squares; n=6),γ-8Δ4/Δ4 (gray squares; n=10) andγ-8+/Δ4 slices (light gray squares; n=9) to a similar degree, but attenuated inγ-8−/−slices (black triangles; n=4). Inset, averaged fEPSPs before (dark trace) and during LTP (light trace). Calibration: 10 ms, 0.5 mV (+/+), 0.45 mV (⊗4/⊗4), 0.38 (+/⊗4) and 0.5 mV (−/−).(e) Whole-cell recordings from CA1 pyramidal cells before and after a pairing protocol (arrow). LTP was induced in slices fromγ-8+/+ (n=5),γ-8+/Δ4 heterozygote (n=4) andγ-8Δ4/Δ4 homozygote mice (n=6). Inset, representative examples of averaged EPSCs recorded before and during LTP. Calibration: 20 ms, 200 pA (+/+), 160 pA (⊗4/ ⊗4) and 200 pA (+/⊗4). All data are given as mean ± s.e.m.; *P < 0.05.
References
- Rouach N, et al. TARP gamma-8 controls hippocampal AMPA receptor number, distribution and synaptic plasticity. Nat Neurosci. 2005;8:1525–1533. - PubMed
- Fukaya M, et al. Abundant distribution of TARP gamma-8 in synaptic and extrasynaptic surface of hippocampal neurons and its major role in AMPA receptor expression on spines and dendrites. Eur J Neurosci. 2006;24:2177–2190. - PubMed
- Zamanillo D, et al. Importance of AMPA receptors for hippocampal synaptic plasticity but not for spatial learning. Science. 1999;284:1805–1811. - PubMed
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