Fbxo45 is a novel synaptic E3 and ubiquitin ligase related to the suppressor of cytokine signaling (SOCS) proteins []. Fbxo45 induces the degradation of a synaptic vesicle-priming factor Munc13-1 via the SPRY domain, thus playing an important role in the regulation of neurotransmission by modulating Munc13-1 at the synapse []. F-box motifs are found in proteins that function as the substrate recognition component of SCF E3 complexes [].