Transmembrane interaction mediates complex formation between peptidase homologues and Kv4 channels.

An asthma-related peptidase homologue (DPP10) may act as an auxiliary subunit of Kv4 channels, similar to DPPX. Here we show that DPP10 preferentially binds to Kv4 channel proteins to increase current density and alter channel gating. DPP10 also forms complexes by themselves and with DPPX in the absence of Kv4 channels. DPP10 mRNA is abundantly expressed in nodose and dorsal root ganglia, suggesting that DPP10 participates in controlling airway reactivity and mechanosensation. The region from the N-terminus to the end of the transmembrane of DPP10 mediates its association with the channel, whereas the S1-S2 portion of the channel is sufficient for complex formation. This N-terminal portion of DPP10 also confers all the gating effects produced by the peptidase homologue. Thus, interaction between transmembranes of DPP10/DPPX and Kv4 channel mediates functional complex formation. We call this protein DPPY, instead of DPP10, because of its revealed role as a Kv4 channel regulator.