Dipeptidyl peptidase-like protein 6 (DPP6), a member of the dipeptidyl aminopeptidase family, plays distinct roles in brain development. Dipeptidyl peptidase-like protein 6 (DPP6) is an auxiliary subunit of the Kv4 family of voltage-gated K(+) channels known to enhance channel surface expression and potently accelerate their kinetics. DPP6 is a single transmembrane protein, which is structurally remarkable for its large extracellular domain. DPP6 is well known as an auxiliary subunit of Kv4-containing, A-type K(+) channels which regulate dendritic excitability in hippocampal CA1 pyramidal neurons. We have recently reported, however, a novel role for DPP6 in regulating dendritic filopodia formation and stability, affecting synaptic development and function.