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Cercós P, Peraza DA, de Benito-Bueno A, Socuéllamos PG, Aziz-Nignan A, Arrechaga-Estévez D, Beato E, Peña-Acevedo E, Albert A, González-Vera JA, Rodríguez Y, Martín-Martínez M, Valenzuela C, Gutiérrez-Rodríguez M. Pharmacological Approaches for the Modulation of the Potassium Channel K V4.x and KChIPs. Int J Mol Sci 2021; 22:ijms22031419. [PMID: 33572566 PMCID: PMC7866805 DOI: 10.3390/ijms22031419] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 01/27/2021] [Accepted: 01/28/2021] [Indexed: 02/06/2023] Open
Abstract
Ion channels are macromolecular complexes present in the plasma membrane and intracellular organelles of cells. Dysfunction of ion channels results in a group of disorders named channelopathies, which represent an extraordinary challenge for study and treatment. In this review, we will focus on voltage-gated potassium channels (KV), specifically on the KV4-family. The activation of these channels generates outward currents operating at subthreshold membrane potentials as recorded from myocardial cells (ITO, transient outward current) and from the somata of hippocampal neurons (ISA). In the heart, KV4 dysfunctions are related to Brugada syndrome, atrial fibrillation, hypertrophy, and heart failure. In hippocampus, KV4.x channelopathies are linked to schizophrenia, epilepsy, and Alzheimer's disease. KV4.x channels need to assemble with other accessory subunits (β) to fully reproduce the ITO and ISA currents. β Subunits affect channel gating and/or the traffic to the plasma membrane, and their dysfunctions may influence channel pharmacology. Among KV4 regulatory subunits, this review aims to analyze the KV4/KChIPs interaction and the effect of small molecule KChIP ligands in the A-type currents generated by the modulation of the KV4/KChIP channel complex. Knowledge gained from structural and functional studies using activators or inhibitors of the potassium current mediated by KV4/KChIPs will better help understand the underlying mechanism involving KV4-mediated-channelopathies, establishing the foundations for drug discovery, and hence their treatments.
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Affiliation(s)
- Pilar Cercós
- Instituto de Química Médica (IQM-CSIC), 28006 Madrid, Spain; (P.C.); (M.M.-M.)
| | - Diego A. Peraza
- Instituto de Investigaciones Biomédicas Alberto Sols (IIBM), CSIC-UAM, 28029 Madrid, Spain; (D.A.P.); (A.d.B.-B.); (P.G.S.)
- Spanish Network for Biomedical Research in Cardiovascular Research (CIBERCV), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Angela de Benito-Bueno
- Instituto de Investigaciones Biomédicas Alberto Sols (IIBM), CSIC-UAM, 28029 Madrid, Spain; (D.A.P.); (A.d.B.-B.); (P.G.S.)
- Spanish Network for Biomedical Research in Cardiovascular Research (CIBERCV), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Paula G. Socuéllamos
- Instituto de Investigaciones Biomédicas Alberto Sols (IIBM), CSIC-UAM, 28029 Madrid, Spain; (D.A.P.); (A.d.B.-B.); (P.G.S.)
- Spanish Network for Biomedical Research in Cardiovascular Research (CIBERCV), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Abdoul Aziz-Nignan
- Department of Natural Sciences, Hostos Community College of CUNY, New York, NY 10451, USA; (A.A.-N.); (D.A.-E.); (E.B.); (E.P.-A.); (Y.R.)
| | - Dariel Arrechaga-Estévez
- Department of Natural Sciences, Hostos Community College of CUNY, New York, NY 10451, USA; (A.A.-N.); (D.A.-E.); (E.B.); (E.P.-A.); (Y.R.)
| | - Escarle Beato
- Department of Natural Sciences, Hostos Community College of CUNY, New York, NY 10451, USA; (A.A.-N.); (D.A.-E.); (E.B.); (E.P.-A.); (Y.R.)
| | - Emilio Peña-Acevedo
- Department of Natural Sciences, Hostos Community College of CUNY, New York, NY 10451, USA; (A.A.-N.); (D.A.-E.); (E.B.); (E.P.-A.); (Y.R.)
| | - Armando Albert
- Instituto de Química Física Rocasolano (IQFR-CSIC), 28006 Madrid, Spain;
| | - Juan A. González-Vera
- Departamento de Físicoquímica, Facultad de Farmacia, Universidad de Granada, 18071 Granada, Spain;
| | - Yoel Rodríguez
- Department of Natural Sciences, Hostos Community College of CUNY, New York, NY 10451, USA; (A.A.-N.); (D.A.-E.); (E.B.); (E.P.-A.); (Y.R.)
| | | | - Carmen Valenzuela
- Instituto de Investigaciones Biomédicas Alberto Sols (IIBM), CSIC-UAM, 28029 Madrid, Spain; (D.A.P.); (A.d.B.-B.); (P.G.S.)
- Spanish Network for Biomedical Research in Cardiovascular Research (CIBERCV), Instituto de Salud Carlos III, 28029 Madrid, Spain
- Correspondence: ; (C.V.); (M.G.-R.); Tel.: +34-91-585-4493 (C.V.); +34-91-258-7493 (M.-G.R.)
| | - Marta Gutiérrez-Rodríguez
- Instituto de Química Médica (IQM-CSIC), 28006 Madrid, Spain; (P.C.); (M.M.-M.)
- Correspondence: ; (C.V.); (M.G.-R.); Tel.: +34-91-585-4493 (C.V.); +34-91-258-7493 (M.-G.R.)
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Peraza DA, Cercós P, Miaja P, Merinero YG, Lagartera L, Socuéllamos PG, Izquierdo García C, Sánchez SA, López-Hurtado A, Martín-Martínez M, Olivos-Oré LA, Naranjo JR, Artalejo AR, Gutiérrez-Rodríguez M, Valenzuela C. Identification of IQM-266, a Novel DREAM Ligand That Modulates K V4 Currents. Front Mol Neurosci 2019; 12:11. [PMID: 30787866 PMCID: PMC6373780 DOI: 10.3389/fnmol.2019.00011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 01/14/2019] [Indexed: 01/30/2023] Open
Abstract
Downstream Regulatory Element Antagonist Modulator (DREAM)/KChIP3/calsenilin is a neuronal calcium sensor (NCS) with multiple functions, including the regulation of A-type outward potassium currents (I A). This effect is mediated by the interaction between DREAM and KV4 potassium channels and it has been shown that small molecules that bind to DREAM modify channel function. A-type outward potassium current (I A) is responsible of the fast repolarization of neuron action potentials and frequency of firing. Using surface plasmon resonance (SPR) assays and electrophysiological recordings of KV4.3/DREAM channels, we have identified IQM-266 as a DREAM ligand. IQM-266 inhibited the KV4.3/DREAM current in a concentration-, voltage-, and time-dependent-manner. By decreasing the peak current and slowing the inactivation kinetics, IQM-266 led to an increase in the transmembrane charge ( Q K V 4.3 / DREAM ) at a certain range of concentrations. The slowing of the recovery process and the increase of the inactivation from the closed-state inactivation degree are consistent with a preferential binding of IQM-266 to a pre-activated closed state of KV4.3/DREAM channels. Finally, in rat dorsal root ganglion neurons, IQM-266 inhibited the peak amplitude and slowed the inactivation of I A. Overall, the results presented here identify IQM-266 as a new chemical tool that might allow a better understanding of DREAM physiological role as well as modulation of neuronal I A in pathological processes.
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Affiliation(s)
- Diego A Peraza
- Instituto de Investigaciones Biomédicas Alberto Sols (IIBM), CSIC-UAM, Madrid, Spain.,Spanish Network for Biomedical Research in Cardiovascular Research (CIBERCV), Instituto de Salud Carlos III, Madrid, Spain
| | - Pilar Cercós
- Instituto de Química Médica (IQM), IQM-CSIC, Madrid, Spain
| | - Pablo Miaja
- Instituto de Investigaciones Biomédicas Alberto Sols (IIBM), CSIC-UAM, Madrid, Spain
| | - Yaiza G Merinero
- Instituto de Investigaciones Biomédicas Alberto Sols (IIBM), CSIC-UAM, Madrid, Spain
| | | | - Paula G Socuéllamos
- Instituto de Investigaciones Biomédicas Alberto Sols (IIBM), CSIC-UAM, Madrid, Spain.,Instituto Universitario de Investigación en Neuroquímica & Departamento de Farmacología y Toxicología, Facultad de Veterinaria, UCM, Madrid, Spain
| | | | - Sara A Sánchez
- Instituto de Investigaciones Biomédicas Alberto Sols (IIBM), CSIC-UAM, Madrid, Spain
| | - Alejandro López-Hurtado
- Centro Nacional de Biotecnología (CNB), CNB-CSIC, Madrid, Spain.,Spanish Network for Biomedical Research in Neurodegenerative Diseases (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain
| | | | - Luis A Olivos-Oré
- Instituto Universitario de Investigación en Neuroquímica & Departamento de Farmacología y Toxicología, Facultad de Veterinaria, UCM, Madrid, Spain
| | - José R Naranjo
- Centro Nacional de Biotecnología (CNB), CNB-CSIC, Madrid, Spain.,Spanish Network for Biomedical Research in Neurodegenerative Diseases (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain
| | - Antonio R Artalejo
- Instituto Universitario de Investigación en Neuroquímica & Departamento de Farmacología y Toxicología, Facultad de Veterinaria, UCM, Madrid, Spain
| | | | - Carmen Valenzuela
- Instituto de Investigaciones Biomédicas Alberto Sols (IIBM), CSIC-UAM, Madrid, Spain.,Spanish Network for Biomedical Research in Cardiovascular Research (CIBERCV), Instituto de Salud Carlos III, Madrid, Spain
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Imai R, Yokota S, Horita S, Ueta Y, Maejima Y, Shimomura K. Excitability of oxytocin neurons in paraventricular nucleus is regulated by voltage-gated potassium channels Kv4.2 and Kv4.3. Biosci Biotechnol Biochem 2019; 83:202-211. [PMID: 30392457 DOI: 10.1080/09168451.2018.1537773] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 10/05/2018] [Indexed: 12/19/2022]
Abstract
Oxytocin is produced by neurons in the paraventricular nucleus (PVN) and the supraoptic nucleus in the hypothalamus. Various ion channels are considered to regulate the excitability of oxytocin neurons and its secretion. A-type currents of voltage-gated potassium channels (Kv channels), generated by Kv4.2/4.3 channels, are known to be involved in the regulation of neuron excitability. However, it is unclear whether the Kv4.2/4.3 channels participate in the regulation of excitability in PVN oxytocin neurons. Here, we investigated the contribution of the Kv4.2/4.3 channels to PVN oxytocin neuron excitability. By using transgenic rat brain slices with the oxytocin-monomeric red fluorescent protein 1 fusion transgene, we examined the excitability of oxytocin neurons by electrophysiological technique. In some oxytocin neurons, the application of Kv4.2/4.3 channel blocker increased firing frequency and membrane potential with extended action potential half-width. Our present study indicates the contribution of Kv4.2/4.3 channels to PVN oxytocin neuron excitability regulation. Abbreviation: PVN, paraventricular nucleus; Oxt-mRFP1, Oxt-monometric red fluorescent protein 1; PaTx-1, Phrixotoxin-1; TEA, Tetraethylammonium Chloride; TTX, tetrodotoxin; aCSF, artificial cerebrospinal fluid;PBS, phosphate buffered saline 3v, third ventricle.
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Affiliation(s)
- Ryota Imai
- a Department of Bioregulation and Pharmacological Medicine , Fukushima Medical University School of Medicine , Fukushima , Japan
- b Tsumura Kampo Research Laboratories, Kampo Research & Development Division , Tsumura & Co ., Ibaraki , Japan
| | - Shoko Yokota
- a Department of Bioregulation and Pharmacological Medicine , Fukushima Medical University School of Medicine , Fukushima , Japan
| | - Shoichiro Horita
- a Department of Bioregulation and Pharmacological Medicine , Fukushima Medical University School of Medicine , Fukushima , Japan
| | - Yoichi Ueta
- c Department of Physiology , School of Medicine, University of Occupational and Environmental Health , Kitakyushu , Japan
| | - Yuko Maejima
- a Department of Bioregulation and Pharmacological Medicine , Fukushima Medical University School of Medicine , Fukushima , Japan
| | - Kenju Shimomura
- a Department of Bioregulation and Pharmacological Medicine , Fukushima Medical University School of Medicine , Fukushima , Japan
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Murphy JG, Hoffman DA. A polybasic motif in alternatively spliced KChIP2 isoforms prevents Ca 2+ regulation of Kv4 channels. J Biol Chem 2019; 294:3683-3695. [PMID: 30622142 DOI: 10.1074/jbc.ra118.006549] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 01/04/2019] [Indexed: 11/06/2022] Open
Abstract
The Kv4 family of A-type voltage-gated K+ channels regulates the excitability in hippocampal pyramidal neuron dendrites and are key determinants of dendritic integration, spike timing-dependent plasticity, long-term potentiation, and learning. Kv4.2 channel expression is down-regulated following hippocampal seizures and in epilepsy, suggesting A-type currents as therapeutic targets. In addition to pore-forming Kv4 subunits, modulatory auxiliary subunits called K+ channel-interacting proteins (KChIPs) modulate Kv4 expression and activity and are required to recapitulate native hippocampal A-type currents in heterologous expression systems. KChIP mRNAs contain multiple start sites and alternative exons that generate considerable N-terminal variation and functional diversity in shaping Kv4 currents. As members of the EF-hand domain-containing neuronal Ca2+ sensor protein family, KChIP auxiliary proteins may convey Ca2+ sensitivity upon Kv4 channels; however, to what degree intracellular Ca2+ regulates KChIP-Kv4.2 complexes is unclear. To answer this question, we expressed KChIP2 with Kv4.2 in HEK293T cells, and, with whole-cell patch-clamp electrophysiology, measured an ∼1.5-fold increase in Kv4.2 current density in the presence of elevated intracellular Ca2+ Intriguingly, the Ca2+ regulation of Kv4 current was specific to KChIP2b and KChIP2c splice isoforms that lack a putative polybasic domain that is present in longer KChIP2a1 and KChIP2a isoforms. Site-directed acidification of the basic residues within the polybasic motif of KChIP2a1 rescued Ca2+-mediated regulation of Kv4 current density. These results support divergent Ca2+ regulation of Kv4 channels mediated by alternative splicing of KChIP2 isoforms. They suggest that distinct KChIP-Kv4 interactions may differentially control excitability and function of hippocampal dendrites.
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Affiliation(s)
- Jonathan G Murphy
- From the NIGMS and .,Section on Molecular Neurophysiology, NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Dax A Hoffman
- Section on Molecular Neurophysiology, NICHD, National Institutes of Health, Bethesda, Maryland 20892
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Derera ID, Smith KC, Smith BN. Altered A-type potassium channel function in the nucleus tractus solitarii in acquired temporal lobe epilepsy. J Neurophysiol 2018; 121:177-187. [PMID: 30517061 DOI: 10.1152/jn.00556.2018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Sudden unexpected death in epilepsy (SUDEP) is among the leading causes of death in people with epilepsy. Individuals with temporal lobe epilepsy (TLE) have a high risk for SUDEP because the seizures are often medically intractable. Neurons in the nucleus tractus solitarii (NTS) have been implicated in mouse models of SUDEP and play a critical role in modulating cardiorespiratory and autonomic output. Increased neuronal excitability of inhibitory, GABAergic neurons in the NTS develops during epileptogenesis, and NTS dysfunction has been implicated in mouse models of SUDEP. In this study we used the pilocarpine-induced status epilepticus model of TLE (i.e., pilo-SE mice) to investigate the A-type voltage-gated K+ channel as a potential contributor to increased excitability in GABAergic NTS neurons during epileptogenesis. Compared with age-matched control mice, pilo-SE mice displayed an increase in spontaneous action potential frequency and half-width 9-12 wk after treatment. Activity of GABAergic NTS neurons from pilo-SE mice showed less sensitivity to 4-aminopyridine. Correspondingly, reduced A-type K+ current amplitude was detected in these neurons, with no change in activation or inactivation kinetics. No changes were observed in Kv4.1, Kv4.2, Kv4.3, KChIP1, KChIP3, or KChIP4 mRNA expression. These changes contribute to the increased excitability in GABAergic NTS neurons that develops in TLE and may provide insight into potential mechanisms contributing to the increased risk for cardiorespiratory collapse and SUDEP in this model. NEW & NOTEWORTHY Sudden unexpected death in epilepsy (SUDEP) is a leading cause of death in epilepsy, and dysfunction in central autonomic neurons may play a role. In a mouse model of acquired epilepsy, GABAergic neurons in the nucleus tractus solitarii developed a reduced amplitude of the A-type current, which contributes to the increased excitability seen in these neurons during epileptogenesis. Neuronal excitability changes in inhibitory central vagal circuitry may increase the risk for cardiorespiratory collapse and SUDEP.
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Affiliation(s)
- Isabel D Derera
- Department of Physiology, College of Medicine, University of Kentucky , Lexington, Kentucky
| | - Katalin Cs Smith
- Department of Physiology, College of Medicine, University of Kentucky , Lexington, Kentucky.,Department of Neuroscience, College of Medicine, University of Kentucky , Lexington, Kentucky
| | - Bret N Smith
- Department of Physiology, College of Medicine, University of Kentucky , Lexington, Kentucky.,Department of Neuroscience, College of Medicine, University of Kentucky , Lexington, Kentucky.,Epilepsy Research Center, University of Kentucky , Lexington, Kentucky
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Lin MA, Cannon SC, Papazian DM. Kv4.2 autism and epilepsy mutation enhances inactivation of closed channels but impairs access to inactivated state after opening. Proc Natl Acad Sci U S A 2018; 115:E3559-68. [PMID: 29581270 DOI: 10.1073/pnas.1717082115] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A de novo mutation in the KCND2 gene, which encodes the Kv4.2 K+ channel, was identified in twin boys with intractable, infant-onset epilepsy and autism. Kv4.2 channels undergo closed-state inactivation (CSI), a mechanism by which channels inactivate without opening during subthreshold depolarizations. CSI dynamically modulates neuronal excitability and action potential back propagation in response to excitatory synaptic input, controlling Ca2+ influx into dendrites and regulating spike timing-dependent plasticity. Here, we show that the V404M mutation specifically affects the mechanism of CSI, enhancing the inactivation of channels that have not opened while dramatically impairing the inactivation of channels that have opened. The mutation gives rise to these opposing effects by increasing the stability of the inactivated state and in parallel, profoundly slowing the closure of open channels, which according to our data, is required for CSI. The larger volume of methionine compared with valine is a major factor underlying altered inactivation gating. Our results suggest that V404M increases the strength of the physical interaction between the pore gate and the voltage sensor regardless of whether the gate is open or closed. Furthermore, in contrast to previous proposals, our data strongly suggest that physical coupling between the voltage sensor and the pore gate is maintained in the inactivated state. The state-dependent effects of V404M on CSI are expected to disturb the regulation of neuronal excitability and the induction of spike timing-dependent plasticity. Our results strongly support a role for altered CSI gating in the etiology of epilepsy and autism in the affected twins.
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Hermanstyne TO, Granados-Fuentes D, Mellor RL, Herzog ED, Nerbonne JM. Acute Knockdown of Kv4.1 Regulates Repetitive Firing Rates and Clock Gene Expression in the Suprachiasmatic Nucleus and Daily Rhythms in Locomotor Behavior. eNeuro 2017; 4:ENEURO. [PMID: 28560311 DOI: 10.1523/ENEURO.0377-16.2017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 04/14/2017] [Accepted: 05/07/2017] [Indexed: 11/23/2022] Open
Abstract
Rapidly activating and inactivating A-type K+ currents (IA) encoded by Kv4.2 and Kv4.3 pore-forming (α) subunits of the Kv4 subfamily are key regulators of neuronal excitability. Previous studies have suggested a role for Kv4.1 α-subunits in regulating the firing properties of mouse suprachiasmatic nucleus (SCN) neurons. To test this, we utilized an RNA-interference strategy to knockdown Kv4.1, acutely and selectively, in the SCN. Current-clamp recordings revealed that the in vivo knockdown of Kv4.1 significantly (p < 0.0001) increased mean ± SEM repetitive firing rates in SCN neurons during the day (6.4 ± 0.5 Hz) and at night (4.3 ± 0.6 Hz), compared with nontargeted shRNA-expressing SCN neurons (day: 3.1 ± 0.5 Hz; night: 1.6 ± 0.3 Hz). IA was also significantly (p < 0.05) reduced in Kv4.1-targeted shRNA-expressing SCN neurons (day: 80.3 ± 11.8 pA/pF; night: 55.3 ± 7.7 pA/pF), compared with nontargeted shRNA-expressing (day: 121.7 ± 10.2 pA/pF; night: 120.6 ± 16.5 pA/pF) SCN neurons. The magnitude of the effect of Kv4.1-targeted shRNA expression on firing rates and IA was larger at night. In addition, Kv4.1-targeted shRNA expression significantly (p < 0.001) increased mean ± SEM nighttime input resistance (Rin; 2256 ± 166 MΩ), compared to nontargeted shRNA-expressing SCN neurons (1143 ± 93 MΩ). Additional experiments revealed that acute knockdown of Kv4.1 significantly (p < 0.01) shortened, by ∼0.5 h, the circadian period of spontaneous electrical activity, clock gene expression and locomotor activity demonstrating a physiological role for Kv4.1-encoded IA channels in regulating circadian rhythms in neuronal excitability and behavior.
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Clark BD, Kwon E, Maffie J, Jeong HY, Nadal M, Strop P, Rudy B. DPP6 Localization in Brain Supports Function as a Kv4 Channel Associated Protein. Front Mol Neurosci 2008; 1:8. [PMID: 18978958 PMCID: PMC2576564 DOI: 10.3389/neuro.02.008.2008] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Accepted: 09/24/2008] [Indexed: 11/13/2022] Open
Abstract
The gene encoding the dipeptidyl peptidase-like protein DPP6 (also known as DPPX) has been associated with human neural disease. However, until recently no function had been found for this protein. It has been proposed that DPP6 is an auxiliary subunit of neuronal Kv4 K(+) channels, the ion channels responsible for the somato-dendritic A-type K(+) current, an ionic current with crucial roles in the regulation of firing frequency, dendritic integration and synaptic plasticity. This view has been supported mainly by studies showing that DPP6 is necessary to generate channels with biophysical properties resembling the native channels in some neurons. However, independent evidence that DPP6 is a component of neuronal Kv4 channels in the brain, and whether this protein has other functions in the CNS is still lacking. We generated antibodies to DPP6 proteins to compare their distribution in brain with that of the Kv4 pore-forming subunits. DPP6 proteins were prominently expressed in neuronal populations expressing Kv4.2 proteins and both types of protein were enriched in the dendrites of these cells, strongly supporting the hypothesis that DPP6 is an associated protein of Kv4 channels in brain neurons. The observed similarity in the cellular and subcellular patterns of expression of both proteins suggests that this is the main function of DPP6 in brain. However, we also found that DPP6 antibodies intensely labeled the hippocampal mossy fiber axons, which lack Kv4 proteins, suggesting that DPP6 proteins may have additional, Kv4-unrelated functions.
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Affiliation(s)
- Brian D Clark
- Smilow Neuroscience Program, Department of Physiology & Neuroscience New York, USA
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