Phosphorylation of the AMPA receptor subunit GluA1 regulates clathrin-mediated receptor internalization

Abstract

Synaptic strength is altered during synaptic plasticity by controlling the number of AMPA receptors (AMPARs) at excitatory synapses. During long-term potentiation and synaptic up-scaling, AMPARs are accumulated at synapses to increase synaptic strength. Neuronal activity leads to phosphorylation of AMPAR subunit GluA1 and subsequent elevation of GluA1 surface expression, either by an increase in receptor forward trafficking to the synaptic membrane or a decrease in receptor internalization. However, the molecular pathways underlying GluA1 phosphorylation-induced elevation of surface AMPAR expression are not completely understood. Here, we employ fluorescence recovery after photobleaching (FRAP) to reveal that phosphorylation of GluA1 Serine 845 (S845) predominantly plays a role in receptor internalization than forward trafficking during synaptic plasticity. Notably, internalization of AMPARs depends upon the clathrin adaptor, AP2, which recruits cargo proteins into endocytic clathrin coated pits. In fact, we further reveal that an increase in GluA1 S845 phosphorylation by two distinct forms of synaptic plasticity diminishes the binding of the AP2 adaptor, reducing internalization, and resulting in elevation of GluA1 surface expression. We thus demonstrate a mechanism of GluA1 phosphorylation-regulated clathrin-mediated internalization of AMPARs.

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“…The copyright holder for this preprint this version posted December 5, 2022. ; https://doi.org/10.1101/2022.12.05.519102 doi: bioRxiv preprint AMPAR trafficking has long been known to be regulated by the phosphorylation of the GluA1 subunit (19). Phosphorylation of serine 845 (S845) in GluA1 promotes GluA1containing AMPAR surface expression, whereas dephosphorylation of S845 is involved in receptor internalization (19,34). We have previously shown that a decrease in neuronal Ca 2+ activity reduces the activity of Ca 2+ -dependent phosphatase calcineurin, increasing GluA1 S845 phosphorylation to induce synaptic expression of CP-AMPARs (35).…”