Jerng HH , Pfaffinger PJ .

R01 GM090029 NIGMS NIH HHS , R01 NS37444 NINDS NIH HHS , P30 HD024064 NICHD NIH HHS , P01 NS037444 NINDS NIH HHS

	Figure 1. Analysis of DPP6 splice variant expression in CG cells.A) DPP6 gene shows a conserved set of four alternative first exons producing the protein variants DPP6a, DPP6K, DPP6L and DPP6S. B) qRT-PCR using SYBR Green Fluorescence for DPP6 variants from three brain regions: cortex, cerebellum and hippocampus. DPP6a and DPP6K show enhanced expression in cerebellum. C) Normalization controls used to correct for primer amplification efficiency differences. Amplification targets from GAPDH and two DPLP variants were diluted and used to construct amplification curves. Common GAPDH signal was used to ensure consistent dilution of standards. D) Relative expression levels of DPP6 variants in cerebellum following normalization. Due to high levels of expression in CG cells and the abundance of these neurons, these signals essentially report the relative expression of DPP6 variants in CG cells.
	Figure 2. DPP6K dramatically accelerates inactivation kinetics and leftward shifts steady-state inactivation curve.Xenopus oocytes were injected with cRNAs encoding Kv4.2 and KChIP3a along with either DPP6a, DPP6S, or DPP6K. Transient currents were recorded using two-electrode voltage clamp. (A) Representative normalized current traces generated by voltage steps to +50 mV from a holding potential of −100 mV for 1 sec. Only the first 500 ms are shown. (B) Voltage dependence of steady-state inactivation for the various channel complexes. The steady-state inactivation protocol consisted of a 10-sec prepulse at the indicated potentials and a 250-ms test pulse to +50 mV, with an inter-episode interval of 5 secs. The fraction of available current (I/Imax) was plotted against the prepulse membrane potential. Data are shown as mean ± SEM, and the lines represent fits using Boltzmann functions.
	Figure 3. DPP6K markedly represses the recovery-accelerating effects of KChIP3a.Representative current traces generated during the two-pulse protocol used to measure recovery from inactivation for Kv4.2+KChIP3a (A), Kv4.2+KChIP3a+DPP6a (B), Kv4.2+KChIP3a+DPP6S (C), and Kv4.2+KChIP3a+DPP6K (D). A 1-sec depolarization to +50 mV was delivered to maximally inactivate the channels, followed by an increasing recovery interval at −100 mV before applying a 250-ms test pulse at +50 mV to check the degree of recovery from inactivation. (E) Fractional recovery was plotted as a function of the interval duration at −100 mV. The residual value at the end the first pulse was subtracted from the peak current values of the first and second pulses, and the fractional recovery was determined by dividing the peak value of the second pulse by that of the first pulse.
	Figure 4. The DPP6K variable N-terminus is responsible for its distinct functional effects.(A) Voltage dependence of steady-state inactivation of ternary complex containing DPP6K and DPP6K/ΔN16 deletion mutant. The protocol was the same as that of Fig. 2B. (B) The kinetics of recovery from inactivation at −100 mV. The protocol was the same as that of Fig. 3. (C) Alignment of amino acid sequences of DPP6K variable N-terminus from various organisms. Consensus residues are shown in black; conservative substitutions, in gray; non-conservative substitutions, in red. Major evolutionary branch points indicated along the alignment relative to a terminus in placental mammals.
	Figure 5. Co-assembly of DPP6K and DPP6a in heteromultimeric channel complexes.(A) Outward currents expressed by oocytes co-injected by various combinations of cRNAs, as elicited by depolarization to +40 mV from holding potential of −100 mV. (B) Expected rise and decay of currents if DPP6a and DPP6K subunits do not co-assemble and produce segregated channel populations containing either one alone. (C) Slowing of the time constant of fast inactivation when DPP6a mRNA changes from 100% to 10% mixed with DPP6K mRNA. To get the average value for fast inactivation, the slow phase of inactivation and non-inactivating current were described by exponential fitting and subtracted from the total current. The remaining average fast inactivation time constant was measured by taking the peak current for the fast inactivating fraction divided by its area. The average time constant measured by this method was very similar to the time constant measured by the best single exponential fit to the fast inactivating component. The black and gray lines show the predicted maximal slowing of fast inactivation with four DPP6 and two DPP6 per channel, respectively, with only 1 DPP6a subunit per channel. (D) Recovery from inactivation at −100 mV after a 200 ms-long prepulse (symbols) as compared to predicted results assuming no co-assembly of DPP6a and DPP6K (dashes).
	Figure 6. Steady-state inactivation of DPP6a∶DPP6K mixed channels.(A) Representative traces for Kv4.2+KChIP3a channels co-expressed with DPP6a alone, DPP6K alone, or with a DPP6a∶DPP6K mixture at 1∶1 or 1∶2 ratios, showing changes in steady-state inactivation at −65 mV. For the colored traces, the channels were held for 30 sec at −65 mV before pulsing to +40 mV for 250 ms to test available current. The black traces show the total currents, from test pulses where the channels were held at −100 mV and experienced no inactivation. (B) Voltage dependence of steady-state inactivation of ternary complexes with homotetrameric and heterotetrameric DPP6 subunits. (C) Progressive shifting of inactivation midpoint with increasing DPP6K ratio. The V0.5i values were plotted against the calculated DPP6K mole fraction. Model assumes independent energetic effects for each DPP6K subunit incorporated into the channel, with symbols measured V0.5i values for summed Boltzmann curves from the model.
	Figure 7. Reconstitution of native ISA channel from CG cells by heterologous expression in oocytes.(A) Outward transient currents elicited from CG cells and oocytes expressing Kv4.2, a mixture of DPP6a and DPP6K at 1∶2 ratio, and either KChIP3a or KChIP4bL. From a holding potential of −100 mV, either a 200-ms (CG cells) or 1-sec (oocytes) step depolarizations were made from −100 mV to +40 mV at 10 mV increments. (B) Overlapped normalized current traces at +40 mV from the indicated channels. (C) Time constants of inactivation at indicated membrane potentials for ISA from CG cells, Kv4.2+KChIP3a+DPP6a+DPP6K (1∶2), and Kv4.2+KChIP4bL+DPP6a+DPP6K (1∶2). (D) Recovery from inactivation at −100 mV, measured using the two-pulse protocol. (E) Normalized peak conductance-voltage relations (Gp/Gp,max) and steady-state inactivation curves (I/Imax) for ISA from CG cells and reconstituted channel complexes.

Amarillo, Ternary Kv4.2 channels recapitulate voltage-dependent inactivation kinetics of A-type K+ channels in cerebellar granule neurons. 2008, Pubmed

Amarillo, Ternary Kv4.2 channels recapitulate voltage-dependent inactivation kinetics of A-type K+ channels in cerebellar granule neurons. 2008, Pubmed
Anderson, Regulation of the KV4.2 complex by CaV3.1 calcium channels. 2010, Pubmed
Anderson, Regulation of neuronal activity by Cav3-Kv4 channel signaling complexes. 2010, Pubmed
Bardoni, Kinetic study and numerical reconstruction of A-type current in granule cells of rat cerebellar slices. 1993, Pubmed
Beck, Remodelling inactivation gating of Kv4 channels by KChIP1, a small-molecular-weight calcium-binding protein. 2002, Pubmed , Xenbase
Clark, DPP6 Localization in Brain Supports Function as a Kv4 Channel Associated Protein. 2008, Pubmed
Connor, Prediction of repetitive firing behaviour from voltage clamp data on an isolated neurone soma. 1971, Pubmed
Covarrubias, The neuronal Kv4 channel complex. 2008, Pubmed
Dougherty, The dipeptidyl-aminopeptidase-like protein 6 is an integral voltage sensor-interacting beta-subunit of neuronal K(V)4.2 channels. 2009, Pubmed
Heinemann, Functional characterization of Kv channel beta-subunits from rat brain. 1996, Pubmed , Xenbase
Hockberger, Immunocytochemical and electrophysiological differentiation of rat cerebellar granule cells in explant cultures. 1987, Pubmed
Hoffman, K+ channel regulation of signal propagation in dendrites of hippocampal pyramidal neurons. 1997, Pubmed
Hu, 4-aminopyridine, a Kv channel antagonist, prevents apoptosis of rat cerebellar granule neurons. 2006, Pubmed
Jerng, DPP10 splice variants are localized in distinct neuronal populations and act to differentially regulate the inactivation properties of Kv4-based ion channels. 2007, Pubmed , Xenbase
Jerng, Multiple Kv channel-interacting proteins contain an N-terminal transmembrane domain that regulates Kv4 channel trafficking and gating. 2008, Pubmed
Jerng, A novel N-terminal motif of dipeptidyl peptidase-like proteins produces rapid inactivation of KV4.2 channels by a pore-blocking mechanism. 2009, Pubmed , Xenbase
Jerng, Modulation of Kv4.2 channel expression and gating by dipeptidyl peptidase 10 (DPP10). 2004, Pubmed , Xenbase
Jerng, Molecular physiology and modulation of somatodendritic A-type potassium channels. 2004, Pubmed
Jerng, Multiprotein assembly of Kv4.2, KChIP3 and DPP10 produces ternary channel complexes with ISA-like properties. 2005, Pubmed , Xenbase
Lacerda, T-type and N-type calcium channels of Xenopus oocytes: evidence for specific interactions with beta subunits. 1994, Pubmed , Xenbase
Liss, Tuning pacemaker frequency of individual dopaminergic neurons by Kv4.3L and KChip3.1 transcription. 2001, Pubmed
MacKinnon, Functional stoichiometry of Shaker potassium channel inactivation. 1993, Pubmed , Xenbase
Maffie, Weighing the evidence for a ternary protein complex mediating A-type K+ currents in neurons. 2008, Pubmed
Maffie, A novel DPP6 isoform (DPP6-E) can account for differences between neuronal and reconstituted A-type K(+) channels. 2009, Pubmed
Nadal, The CD26-related dipeptidyl aminopeptidase-like protein DPPX is a critical component of neuronal A-type K+ channels. 2003, Pubmed , Xenbase
Nadal, Differential characterization of three alternative spliced isoforms of DPPX. 2006, Pubmed , Xenbase
Nadin, Dipeptidyl peptidase-like protein 6 is required for normal electrophysiological properties of cerebellar granule cells. 2010, Pubmed
Pioletti, Three-dimensional structure of the KChIP1-Kv4.3 T1 complex reveals a cross-shaped octamer. 2006, Pubmed , Xenbase
Pruunsild, Structure, alternative splicing, and expression of the human and mouse KCNIP gene family. 2005, Pubmed
Qi, Cloning and characterization of dipeptidyl peptidase 10, a new member of an emerging subgroup of serine proteases. 2003, Pubmed
Ramakers, A postsynaptic transient K(+) current modulated by arachidonic acid regulates synaptic integration and threshold for LTP induction in hippocampal pyramidal cells. 2002, Pubmed
Rettig, Inactivation properties of voltage-gated K+ channels altered by presence of beta-subunit. 1994, Pubmed , Xenbase
Rhodes, KChIPs and Kv4 alpha subunits as integral components of A-type potassium channels in mammalian brain. 2004, Pubmed
Robello, A transient voltage-dependent outward current in cultured cerebellar granules. 1989, Pubmed
Rossi, Age-dependent expression of high-voltage activated calcium currents during cerebellar granule cell development in situ. 1994, Pubmed
Savalli, Modes of operation of the BKCa channel beta2 subunit. 2007, Pubmed , Xenbase
Serôdio, Cloning of a novel component of A-type K+ channels operating at subthreshold potentials with unique expression in heart and brain. 1996, Pubmed , Xenbase
Serôdio, Differential expression of Kv4 K+ channel subunits mediating subthreshold transient K+ (A-type) currents in rat brain. 1998, Pubmed
Shibata, A fundamental role for KChIPs in determining the molecular properties and trafficking of Kv4.2 potassium channels. 2003, Pubmed
Soh, I SA channel complexes include four subunits each of DPP6 and Kv4.2. 2008, Pubmed , Xenbase
Stefani, A-current in rat globus pallidus: a whole-cell voltage clamp study on acutely dissociated neurons. 1992, Pubmed
Strassle, Light and electron microscopic analysis of KChIP and Kv4 localization in rat cerebellar granule cells. 2005, Pubmed
Strop, Structure of a human A-type potassium channel interacting protein DPPX, a member of the dipeptidyl aminopeptidase family. 2004, Pubmed
Takimoto, Species and tissue differences in the expression of DPPY splicing variants. 2006, Pubmed
Takimoto, Palmitoylation of KChIP splicing variants is required for efficient cell surface expression of Kv4.3 channels. 2002, Pubmed
Talley, Differential distribution of three members of a gene family encoding low voltage-activated (T-type) calcium channels. 1999, Pubmed
Tkatch, Kv4.2 mRNA abundance and A-type K(+) current amplitude are linearly related in basal ganglia and basal forebrain neurons. 2000, Pubmed
van Es, Genetic variation in DPP6 is associated with susceptibility to amyotrophic lateral sclerosis. 2008, Pubmed
Wada, Differential expression of two distinct forms of mRNA encoding members of a dipeptidyl aminopeptidase family. 1992, Pubmed
Wang, Elevation of intracellular Ca2+ modulates A-currents in rat cerebellar granule neurons. 2005, Pubmed
Wang, Structural basis for modulation of Kv4 K+ channels by auxiliary KChIP subunits. 2007, Pubmed , Xenbase
Watanabe, Dendritic K+ channels contribute to spike-timing dependent long-term potentiation in hippocampal pyramidal neurons. 2002, Pubmed
Xia, Inactivation of BK channels by the NH2 terminus of the beta2 auxiliary subunit: an essential role of a terminal peptide segment of three hydrophobic residues. 2003, Pubmed , Xenbase
Xiong, Differential distribution of KChIPs mRNAs in adult mouse brain. 2004, Pubmed
Zagha, DPP10 modulates Kv4-mediated A-type potassium channels. 2005, Pubmed
Zegarra-Moran, Properties of the transient potassium currents in cerebellar granule cells. 1994, Pubmed