Component of a SCF (SKP1-CUL1-F-box protein) E3 ubiquitin ligase complex which may regulate restriction and/or maturation of synapses. Protein modification; protein ubiquitination. Component of a SCF (SKP1-CUL1-F-box protein) E3 ubiquitin ligase complex. Belongs to the FBXO45/Fsn family.