Modulation of Kv4.2 Channel Expression and Gating by Dipeptidyl Peptidase 10 (DPP10)

Abstract

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 (taurec: WT = 200 ms, +DPP10 = 78 ms). Furthermore, DPP10 introduced hyperpolarizing shifts in the conductance-voltage relationship (approximately 19 mV) as well as steady-state inactivation (approximately 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.

Kv4.2 autism and epilepsy mutation enhances inactivation of closed channels but impairs access to inactivated state after opening

“…Plasmid cDNA clones of human KChIP3a and DPP6s were provided by Paul J. Pfaffinger, Baylor College of Medicine, Houston, and Manuel Covarrubias, Thomas Jefferson University, Philadelphia, respectively (36,66). RNA encoding wild-type or mutant Kv4.2 was mixed at a 1:1 molar ratio with RNA encoding KChIP3a and injected into Xenopus laevis oocytes for functional analysis using a two-electrode voltage clamp (43,44).…”

Multiple Kv Channel-interacting Proteins Contain an N-terminal Transmembrane Domain That Regulates Kv4 Channel Trafficking and Gating

“…Rat Kv4.2 cDNA in pBluescript SK was obtained as previously described (4). Human KChIP3a and KChIP4b-L cDNAs were purchased from the American Type Culture Collection (Manassas, VA) and maintained in pT7T3D-Pac and pBSR, respectively.…”

“…HEK293T cells were transfected using Lipofectamine 2000 reagent (Invitrogen), following precisely the manufacturer's protocols. Heterologous expression of proteins was tested 48 h after transfection by Western blot analysis, following a previously described protocol (4). Primary anti-pan-KChIP (K55/82; Antibodies Inc., Davis, CA), anti-eGFP (3E6; Invitrogen), antiKChIP3 (FL-214; Santa Cruz Biotechnology, Inc., Santa Cruz, CA), and anti-DPP6 antibodies (ab41811; Abcam; Cambridge, MA) were used at 1:1000 dilutions.…”

KV4.3 N-terminal deletion mutant D2-39

“…In addition to KChIPs, several additional β subunits may also be physiologically relevant modulators of K V 4 channels. 3,8 Such additional β subunits include dipeptidyl-aminopeptidase-like proteins (DPPX isoforms), [50][51][52][53][54][55] Min-K related peptides (MiRPs), [56][57][58][59][60] and K V β isoforms. 57,61,62 All of these " fit with τ = 108 ms; blue curve, truncated single exponential beginning at Δt = 60 ms with τ = 126 ms. Gray symbols and fits correspond to WT (solid circles) and Δ2-39 (hollow circles) obtained in the absence of KChIp2b (previously illustrated in Fig.…”

“…3,8,[50][51][52][53][54][55][56][57][58][59][60][61][62] However, for reasons to be addressed in Discussion, our coexpression studies focused exclusively on KChIP2b.…”