GluN2B suppression restores phenylalanine-induced neuroplasticity and cognition impairments in a mouse model of phenylketonuria
Woo Seok Song, … , Jae Min Lim, Myoung-Hwan Kim
Woo Seok Song, … , Jae Min Lim, Myoung-Hwan Kim
Published May 8, 2025
Citation Information: J Clin Invest. 2025;135(13):e184299. https://doi.org/10.1172/JCI184299.
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Research Article Metabolism Neuroscience

GluN2B suppression restores phenylalanine-induced neuroplasticity and cognition impairments in a mouse model of phenylketonuria

Abstract

Phenylketonuria (PKU), an inborn error of phenylalanine (Phe) metabolism, is a common cause of intellectual disability. However, the mechanisms by which elevated Phe levels cause cognitive impairment remain unclear. Here, we show that submillimolar Phe perturbs synaptic plasticity through the hyperactivation of GluN2B-containing NMDARs. PahEnu2 PKU model mice exhibited submillimolar and supramillimolar concentrations of Phe in the cerebrospinal fluid (CSF) and serum, respectively. l-Phe produced concentration-dependent bidirectional effects on NMDA-induced currents, without affecting synaptic NMDA receptors (NMDARs) in hippocampal CA1 neurons. l-Phe-induced hyperactivation of extrasynaptic GluN2B resulted in activity-dependent downregulation of AMPA receptors during burst or sustained synaptic activity. Administration of l-Phe in mice decreased neural activity and impaired memory, which were blocked by pretreatment with GluN2B inhibitors. Furthermore, pharmacological and virus-mediated suppression of GluN2B reversed the impaired learning in PahEnu2 mice. Collectively, these results suggest the concentration of Phe in the CSF of patients with PKU perturbs extrasynaptic NMDARs and synaptic plasticity and that suppression of GluN2B may have the potential to improve cognitive function in patients with PKU.

Authors

Woo Seok Song, Young Sook Kim, Young-Soo Bae, Sang Ho Yoon, Jae Min Lim, Myoung-Hwan Kim

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Figure 3

l-Phe perturbs synaptic plasticity through the activity-dependent downregulation of AMPARs.

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l-Phe perturbs synaptic plasticity through the activity-dependent downr...
(A) l-Phe reduces the magnitude of LTP in both WT and PahEnu2 mice. Top: representative traces of fEPSP obtained at the indicated time points. Bottom left: fEPSP slopes were normalized to those obtained in the baseline and plotted against time. l-Phe was perfused from 5 minutes before to 1 minutes after TBS (arrow). Bottom right: fEPSP slopes during the last 10 minutes were normalized to baseline. (B) GluN2B antagonists block the effect of l-Phe on the TBS (arrow)-induced LTP. Sample traces (top), time course of fEPSP slopes (bottom left), and the magnitude of LTP (bottom right) in each condition. (C and D) PEAQX blocks LTP induction, and l-Phe perfusion during the peri-TBS period induces an LTD-like decrease in fEPSP slopes. (E and F) l-Phe and TBS had no effect on the slope of fEPSPs under GluN2A and GluN2B inhibition. (G−K) Representative Western blots (G), and the ratios of phosphorylated GluA1-S845 to total GluA1 (H), total GluA1 to -tubulin (I), phosphorylated GluA2-S880 to total GluA2 (J), and total GluA2 to -tubulin (K) in the CA1 region of acute hippocampal sections harvested 30 minutes after TBS. (L) WT and PahEnu2 sections exhibit similar synaptic responses to LFS. (M) Normalized fEPSP slopes during the last 10 minutes in WT and PahEnu2 sections. (N) Ro blocks the effect of l-Phe on LTD facilitation. Sample traces of fEPSPs (top). (O) Normalized fEPSP slopes during the last 10 minutes in each condition. (A−C, E, L, and N) Scale bars: 5 ms and 0.5 mV. Statistical analysis was performed using Student’s t test (D, F, and M), 1-way (H−K, and O) or 2-way ANOVA (A), or Kruskal-Wallis test (B) with post hoc Tukey’s test. *P < 0.05, **P < 0.01, ***P < 0.001, and NS, P ≥ 0.05. Con, control; Veh, vehicle.