Excess ribosomal protein production unbalances translation in a model of Fragile X Syndrome.

Seo, Sang S; Louros, Susana R; Anstey, Natasha; Gonzalez-Lozano, Miguel A; Harper, Callista B; Verity, Nicholas C; Dando, Owen; Thomson, Sophie R et al. · Nat Commun · 2022

basic_science · Level V

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Abstract

Dysregulated protein synthesis is a core pathogenic mechanism in Fragile X Syndrome (FX). The mGluR Theory of FX predicts that pathological synaptic changes arise from the excessive translation of mRNAs downstream of mGlu<sub>1/5</sub> activation. Here, we use a combination of CA1 pyramidal neuron-specific TRAP-seq and proteomics to identify the overtranslating mRNAs supporting exaggerated mGlu<sub>1/5</sub> -induced long-term synaptic depression (mGluR-LTD) in the FX mouse model (Fmr1<sup>-/y</sup>). Our results identify a significant increase in the translation of ribosomal proteins (RPs) upon mGlu<sub>1/5</sub> stimulation that coincides with a reduced translation of long mRNAs encoding synaptic proteins. These changes are mimicked and occluded in Fmr1<sup>-/y</sup> neurons. Inhibiting RP translation significantly impairs mGluR-LTD and prevents the length-dependent shift in the translating population. Together, these results suggest that pathological changes in FX result from a length-dependent alteration in the translating population that is supported by excessive RP translation.

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