A Small Interfering Peptide Potentiates AMPA Receptor Diffusional Trapping and Prevents Social-Isolation-Induced Forgetting of Fear Memory
Synaptic trapping of AMPA receptors (AMPARs) is a key mechanism regulating excitatory synaptic transmission and activity-dependent plasticity underlying learning and memory. Destabilization of synaptic AMPARs is increasingly implicated in cognitive dysfunction across neurological and neuropsychiatric disorders, yet strategies to directly modulate this process in vivo remain limited, constraining both mechanistic insight and therapeutic development. Here we present a peptide-based strategy to enhance AMPAR synaptic trapping by targeting the interaction between transmembrane AMPA receptor regulatory proteins (TARPs) and activity-regulated cytoskeleton-associated protein (ARC/Arg3.1). We designed a 21-amino-acid TAT-fused peptide (TARP-pep) mimicking the TARP C-terminal motif that binds the ARC N-lobe. TARP-pep disrupted the TARP-ARC interaction and increased the stabilization of AMPARs at synaptic surfaces in cultured hippocampal neurons. In vivo, acute intrahippocampal infusion of TARP-pep enhanced perforant path-evoked synaptic transmission in the rat dentate gyrus (DG) and strengthened the interaction between TARPs and postsynaptic density protein 95 (PSD-95), a key mechanism underlying AMPAR anchoring. Consistent with a long-term potentiation (LTP)-like synaptic state, TARP-pep increased basal phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and occluded further chemical LTP (cLTP)-induced increases in phosphorylated CaMKII (p-CaMKII). Notably, a 7-day regimen of daily bilateral DG injections of TARP-pep prevented social isolation (SI)-induced impairment of fear memory in mice. Together, these findings identify the TARP-ARC interaction as a druggable regulator of AMPAR diffusional trapping and highlight synaptic AMPAR stabilization as a promising therapeutic strategy for preserving cognitive function under conditions of circuit vulnerability.