SENP3 deSUMOylase controls coding-region-dependent GluA1 mRNA stability
AMPA-type glutamate receptor subunit GluA1 is a key determinant of excitatory synaptic transmission and plasticity, yet the post-transcriptional mechanisms governing its expression remain incompletely understood. Here, we identify the SUMO-specific protease SENP3 as a previously unrecognized regulator of GluA1 mRNA stability. Conditional deletion of Senp3 in CaMKIIalpha-positive forebrain excitatory neurons selectively increased GluA1 expression in the cortex, hippocampus, and amygdala and was accompanied by elevated membrane-associated and cell-surface GluA1 abundance. Mechanistically, SENP3 depletion increased GluA1 expression by stabilizing its mRNA, without measurably altering GluA1 protein degradation or the activity of the tested Gria1 proximal promoter region. Mapping analyses showed that this regulation was independent of the tested 5' and 3' untranslated regions and required the M4-encoding region of the GluA1 coding sequence (CDS). RNA affinity purification and mass spectrometry revealed that SENP3 associates with the GluA1 messenger ribonucleoproteins (mRNPs). However, ultraviolet crosslinking followed by purification under denaturing conditions did not retain SENP3 as a stable direct GluA1 RNA-binding protein, suggesting a protein-mediated association. Importantly, rescue experiments demonstrated that wild-type SENP3, but not a catalytically inactive mutant, reversed GluA1 upregulation caused by SENP3 depletion. These findings establish SENP3 as a deSUMOylation-dependent post-transcriptional regulator of GluA1 and support a model in which SENP3 promotes GluA1 mRNA turnover by regulating SUMO-sensitive mRNPs associated with the M4-encoding region of the GluA1 CDS.