ANATOMY OF A SUBUNIT: GLUA3 IN SYNAPTIC ACTIVITY AND NEURONAL STRUCTURE

AMPA-type glutamate receptors (AMPARs) are tetrameric cation-permeable channels composed of GluA1–GluA4 subunits that mediate fast excitatory neurotransmission. GluA3, encoded by the GRIA3 gene, has been linked to neurodevelopmental disorders, yet its specific role at glutamatergic synapses remains poorly defined.

Here, we investigated the function of GluA3 using shRNA-mediated knockdown in primary hippocampal neurons. Silencing GluA3 at day in vitro 10 (DIV10) induced marked postsynaptic alterations, including changes in dendritic spine morphology and reduced expression of GluA1 and NMDAR2B. Functionally, GluA3 depletion decreased spontaneous calcium transients independently of presynaptic glutamate release, while single-spine stimulation triggered exaggerated potentiation, indicating disrupted synaptic homeostasis. Transcriptomic analysis revealed dysregulation of activity-dependent genes, including CAMK2A and MAPK3, identifying GluA3 as a critical regulator of intracellular signalling downstream of synaptic activity. In parallel, GluA3 knockdown caused a pronounced reduction in dendritic arbor complexity, suggesting that synaptic dysfunction may reverberate onto neuronal structure. Consistently, in vivo GluA3 silencing in the dorsal CA1 hippocampus of young adult male mice recapitulated the dendritic arbor defects observed in vitro.

Notably, these effects were highly time-dependent: silencing at DIV3 produced more pronounced phenotypes than at DIV10, while knockdown at DIV14 had minimal impact.

Our findings uncover a temporally precise role for GluA3 in shaping synaptic activity, intracellular signalling, and neuronal architecture. Given the role of GRIA3 variants in neurodevelopmental disorders, this work offers new insights into GluA3-related pathologies and may guide targeted therapies.