eIF2α-mediated translational control regulates the persistence of cocaine-induced LTP in midbrain dopamine neurons
- Baylor College of Medicine, United States
- McGill University, Canada
- SBP Medical Discovery Institute, United States
- Mahoney Institute for Neurosciences, Perelman School of Medicine, United States
- Howard Hughes Medical Institute, University of California at San Francisco, United States
Figures
Figure 1
Acute and repeated exposure to cocaine reduces p-eIF2α levels in the VTA.
(a) Schematic of experimental design. (b-c) Both single (10 mg/kg; p<0.001, n = 6 per group, t10 = 4.640) or multiple (five) injections of cocaine (10 mg/kg, p<0.05, n = 3 per group, t4 = 4.329) reduced p-eIF2α levels in the VTA of adult mice.
Figure 2 with 2 supplements
Reduced p-eIF2α levels render cocaine-induced LTP persistent in VTA DA neurons of adult mice.
(a–c) Increased AMPAR/NMDAR ratios lasted only five days in cocaine-injected WT mice (10 mg/kg; 5d, p<0.01, n = 11/9/10 saline/5d cocaine/14d cocaine, F2,27 = 7.82), but persisted >14 days in cocaine-injected Eif2s1S/A mice (5d, p<0.001; 14d, p<0.001, n = 9/8/10 saline/5d cocaine/14d cocaine, F2,24 = 13.31). (d–f) Similarly, cocaine (10 mg/kg, i.p.) increased AMPAR/NMDAR ratio in GFP-positive cells (in which eIF2α cannot be phosphorylated), both at five and at 14 days post-injection (5d, p<0.001; 14d, p<0.001 , n = 5/6/6 saline/5d cocaine/14d cocaine, F2,14 = 8.30), compared to control GFP-negative cells (5d, p<0.05, n = 5/8/5 saline/5d cocaine/14d cocaine, F2,15 = 4.78) from Eif2s1A/A;ftg mice.
Figure 2—figure supplement 1
In Eif2s1S/A mice, cocaine induced LTP in VTA DA neurons persisted for 40 days.
Average AMPAR/NMDAR ratios are shown for adult wild-type control littermates (gray bars, n = 11/11 saline/40d cocaine) or adult Eif2s1S/A mutant mice (green bars, n = 9/5 saline/40d cocaine). Forty days after i.p. cocaine injections (10 mg/kg), a significant LTP was observed in VTA DA neurons from Eif2s1S/A mice, but not in control littermates (p<0.05, n = 11/5 WT 40d cocaine/Eif2s1S/A 40d cocaine, t14 = 2.25, ).
Figure 2—figure supplement 2
Selective absence of eIF2α phosphorylation in VTA enhances persistence of cocaine-induced LTP.
(a) Schematic of experiments. Left: in Eif2s1A/A;ftg mice, both alleles of endogenous gene are mutated (Ser51Ala), and exogenous ftg transgene is expressed containing WT Eif2s1 and a stop signal flanked by two loxP sites that are followed by EGFP. When neurons are infected with AAV virus expressing Cre, the exogenous WT Eif2s1 and the stop signal are cleaved by Cre recombinase, enabling the expression of EGFP. Right: illustration of simultaneous recordings from GFP positive and negative VTA neurons
Figure 3 with 1 supplement
Reduction of eIF2α phosphorylation enhances the persistence of cocaine-induced AMPAR inward rectification.
(a–b) Representative AMPAR EPSCs traces for each group recorded at −70 and +40 mV. I-V plots (c–d) and summaries (e) illustrate that cocaine-induced rectification lasts only five days in control mice (5d, p<0.001, n = 12/10/7 saline/5d cocaine/14d cocaine, F2,26 = 32.02) but persists at least 14 days in Eif2s1S/A mice (5d, p<0.05; 14d, p<0.05, n = 8/8/10 saline/5d cocaine/14d cocaine, F2,23 = 17.21).
Figure 3—figure supplement 1
At 14 days post-injection, polyamines inhibit AMPAR EPSCs only in cocaine-treated Eif2s1S/A mice.
(a) At 14 days after cocaine injection, Joro Spider Toxin (JST, 500 nM), a polyamine that blocks GluR2-lacking AMPA current, depressed EPSCs (recorded at −70 mV) in VTA neurons from Eif2s1S/A mice (p<0.001, n = 5, t8 = 23.67), but not in neurons from control littermates (p = 0.42, n = 5, t8 = 0.857). (b) At 14 days after cocaine injection, 1-Naphthyl acetyl spermine (NASPM, 50 μM), a synthetic analog of JST that also blocks GluR2-lacking AMPA current, depressed EPSCs (recorded at −70 mV) in VTA neurons from Eif2s1S/A mice (p<0.01, n = 5, t8 = 5.992), but not in neurons from control littermates (p = 0.22, n = 5, t8 = 1.441).
Figure 4
Reduced p-eIF2α-mediated translation enhances the persistence of cocaine-induced LTP and rectification in VTA DA neurons.
(a–c) Cocaine-induced increase in AMPAR/NMDAR ratios lasted only five days in control mice (5d, p<0.05, n = 5/5/5 saline/5d cocaine/14d cocaine, F2,12 = 8.38), but persisted at least 14 days in ISRIB-injected mice (5d, p<0.05; 14d, p<0.05, n = 5/5/5 saline/5d cocaine/14d cocaine, F2,12 = 6.40). (d–e) Representative AMPAR EPSCs traces and AMPAR/NMDAR ratios. I-V plots (f–g) and summaries (h) illustrate that cocaine-induced rectification lasts only five days in vehicle-injected mice (5d, p<0.05, n = 4/4/4 saline/5d cocaine/14d cocaine, F2,9 = 7.12), but persists at least 14 days in ISRIB-injected mice (5d, p<0.05; 14d, p<0.05, n = 4/4/4 saline/5d cocaine/14d cocaine, F2,9 = 7.53). (i) Knocking down OPHN1 in the VTA prolonged cocaine-induced LTP to 14 days after cocaine withdrawal (p<0.001, n = 9/8 control-shRNA/Ophn1-shRNA, t15 = 4.986).
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eIF2α-mediated translational control regulates the persistence of cocaine-induced LTP in midbrain dopamine neurons
eLife 5:e17517.
https://doi.org/10.7554/eLife.17517
