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Division of Neuroscience, Baylor College of Medicine, Houston, Texas
Correspondence: Address reprint requests to Henry H. Jerng, Division of Neuroscience, Baylor College of Medicine, One Baylor Plaza S630, Houston, TX 77030. Tel.: 713-798-3062; Fax: 713-798-3946; E-mail: hjerng{at}cns.bcm.tmc.edu.
The dipeptidyl aminopeptidase-like protein DPPX (DPP6) associates with Kv4 potassium channels, increasing surface trafficking and reconstituting native neuronal ISA-like properties. Dipeptidyl peptidase 10 (DPP10) shares with DPP6 a high amino acid identity, lack of enzymatic activity, and expression predominantly in the brain. We used a two-electrode voltage-clamp and oocyte expression system to determine if DPP10 also interacts with Kv4 channels and modulates their expression and function. Kv4.2 coimmunoprecipitated with HA/DPP10 from extracts of oocytes heterologously expressing both proteins. Coexpression with DPP10 and HA/DPP10 enhanced Kv4.2 current by approximately fivefold without increasing protein level. DPP10 also remodeled Kv4.2 kinetic and steady-state properties by accelerating time courses of inactivation and recovery (
rec: WT = 200 ms, +DPP10 = 78 ms). Furthermore, DPP10 introduced hyperpolarizing shifts in the conductance-voltage relationship (
19 mV) as well as steady-state inactivation (7 mV). The effects of DPP10 on Kv4.1 were similar to Kv4.2; however, distinct biophysical differences were observed. Additional experiments suggested that the cytoplasmic N-terminal domain of DPP10 determines the acceleration of inactivation. In summary, DPP10 is a potent modulator of Kv4 expression and biophysical properties and may be a critical component of somatodendritic ISA channels in the brain.
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