Background information
FBXL20 is a member of the F-box protein family, which are characterized by an approximately 40-amino acid F-box motif. SCF complexes, formed by SKP1, cullin, and F-box proteins, act as protein-ubiquitin ligases. FBXL20 is selectively expressed in the brain, broadly expressed within the mouse CNS and is abundant at presynaptic membrane. FBXL20 has orthologs in C. elegans, D. melanogaster, and mammals which suggests that it might function as an important membrane-localized E3 ligase in various species. FBXL20 is a major presynaptic E3 ubiquitin ligase that acts through RIM1a via degradation and the ubiquitin-proteasome-system (UPS) pathway to critically regulate synaptic transmission. This identifies protein degradation as a mechanism for holding synaptic communication in check.