1
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Fnu G, Weber GF. Alterations of Ion Homeostasis in Cancer Metastasis: Implications for Treatment. Front Oncol 2022; 11:765329. [PMID: 34988012 PMCID: PMC8721045 DOI: 10.3389/fonc.2021.765329] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 11/23/2021] [Indexed: 12/20/2022] Open
Abstract
We have previously reported that metastases from all malignancies are characterized by a core program of gene expression that suppresses extracellular matrix interactions, induces vascularization/tissue remodeling, activates the oxidative metabolism, and alters ion homeostasis. Among these features, the least elucidated component is ion homeostasis. Here we review the literature with the goal to infer a better mechanistic understanding of the progression-associated ionic alterations and identify the most promising drugs for treatment. Cancer metastasis is accompanied by skewing in calcium, zinc, copper, potassium, sodium and chloride homeostasis. Membrane potential changes and water uptake through Aquaporins may also play roles. Drug candidates to reverse these alterations are at various stages of testing, with some having entered clinical trials. Challenges to their utilization comprise differences among tumor types and the involvement of multiple ions in each case. Further, adverse effects may become a concern, as channel blockers, chelators, or supplemented ions will affect healthy and transformed cells alike.
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Affiliation(s)
- Gulimirerouzi Fnu
- College of Pharmacy, University of Cincinnati Academic Health Center, Cincinnati, OH, United States
| | - Georg F Weber
- College of Pharmacy, University of Cincinnati Academic Health Center, Cincinnati, OH, United States
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2
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Lamothe SM, Kurata HT. Slc7a5 alters Kvβ-mediated regulation of Kv1.2. J Gen Physiol 2021; 152:151687. [PMID: 32311044 PMCID: PMC7335012 DOI: 10.1085/jgp.201912524] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 01/22/2020] [Accepted: 03/13/2020] [Indexed: 01/15/2023] Open
Abstract
The voltage-gated potassium channel Kv1.2 plays a pivotal role in neuronal excitability and is regulated by a variety of known and unknown extrinsic factors. The canonical accessory subunit of Kv1.2, Kvβ, promotes N-type inactivation and cell surface expression of the channel. We recently reported that a neutral amino acid transporter, Slc7a5, alters the function and expression of Kv1.2. In the current study, we investigated the effects of Slc7a5 on Kv1.2 in the presence of Kvβ1.2 subunits. We observed that Slc7a5-induced suppression of Kv1.2 current and protein expression was attenuated with cotransfection of Kvβ1.2. However, gating effects mediated by Slc7a5, including disinhibition and a hyperpolarizing shift in channel activation, were observed together with Kvβ-mediated inactivation, indicating convergent regulation of Kv1.2 by both regulatory proteins. Slc7a5 influenced several properties of Kvβ-induced inactivation of Kv1.2, including accelerated inactivation, a hyperpolarizing shift and greater extent of steady-state inactivation, and delayed recovery from inactivation. These modified inactivation properties were also apparent in altered deactivation of the Kv1.2/Kvβ/Slc7a5 channel complex. Taken together, these findings illustrate a functional interaction arising from simultaneous regulation of Kv1.2 by Kvβ and Slc7a5, leading to powerful effects on Kv1.2 expression, gating, and overall channel function.
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Affiliation(s)
- Shawn M Lamothe
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Harley T Kurata
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
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3
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Drulis-Fajdasz D, Gostomska-Pampuch K, Duda P, Wiśniewski JR, Rakus D. Quantitative Proteomics Reveals Significant Differences between Mouse Brain Formations in Expression of Proteins Involved in Neuronal Plasticity during Aging. Cells 2021; 10:2021. [PMID: 34440790 PMCID: PMC8393337 DOI: 10.3390/cells10082021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 07/30/2021] [Accepted: 08/05/2021] [Indexed: 12/22/2022] Open
Abstract
Aging is associated with a general decline in cognitive functions, which appears to be due to alterations in the amounts of proteins involved in the regulation of synaptic plasticity. Here, we present a quantitative analysis of proteins involved in neurotransmission in three brain regions, namely, the hippocampus, the cerebral cortex and the cerebellum, in mice aged 1 and 22 months, using the total protein approach technique. We demonstrate that although the titer of some proteins involved in neurotransmission and synaptic plasticity is affected by aging in a similar manner in all the studied brain formations, in fact, each of the formations represents its own mode of aging. Generally, the hippocampal and cortical proteomes are much more unstable during the lifetime than the cerebellar proteome. The data presented here provide a general picture of the effect of physiological aging on synaptic plasticity and might suggest potential drug targets for anti-aging therapies.
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Affiliation(s)
- Dominika Drulis-Fajdasz
- Department of Molecular Physiology and Neurobiology, University of Wrocław, Sienkiewicza 21, 50-335 Wrocław, Poland; (D.D.-F.); (P.D.)
| | - Kinga Gostomska-Pampuch
- Biochemical Proteomics Group, Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany; (K.G.-P.); (J.R.W.)
- Department of Biochemistry and Immunochemistry, Wrocław Medical University, Chałubińskiego 10, 50-368 Wrocław, Poland
| | - Przemysław Duda
- Department of Molecular Physiology and Neurobiology, University of Wrocław, Sienkiewicza 21, 50-335 Wrocław, Poland; (D.D.-F.); (P.D.)
| | - Jacek Roman Wiśniewski
- Biochemical Proteomics Group, Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany; (K.G.-P.); (J.R.W.)
| | - Dariusz Rakus
- Department of Molecular Physiology and Neurobiology, University of Wrocław, Sienkiewicza 21, 50-335 Wrocław, Poland; (D.D.-F.); (P.D.)
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4
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Pisani C, Onori A, Gabanella F, Di Certo MG, Passananti C, Corbi N. Identification of protein/mRNA network involving the PSORS1 locus gene CCHCR1 and the PSORS4 locus gene HAX1. Exp Cell Res 2021; 399:112471. [PMID: 33417922 DOI: 10.1016/j.yexcr.2021.112471] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 12/22/2020] [Accepted: 12/30/2020] [Indexed: 01/22/2023]
Abstract
CCHCR1 (Coiled-Coil alpha-Helical Rod 1), maps to chromosomal region 6p21.3, within the major psoriasis susceptibility locus PSORS1. CCHCR1 itself is a plausible psoriasis candidate gene, however its role in psoriasis pathogenesis remains unclear. We previously demonstrated that CCHCR1 protein acts as a cytoplasmic docking site for RNA polymerase II core subunit 3 (RPB3) in cycling cells, suggesting a role for CCHCR1 in vesicular trafficking between cellular compartments. Here, we report a novel interaction between CCHCR1 and the RNA binding protein HAX1. HAX1 maps to chromosomal region 1q21.3 within the PSORS4 locus and is over-expressed in psoriasis. Both CCHCR1 and HAX1 share subcellular co-localization with mitochondria, nuclei and cytoplasmic vesicles as P-bodies. By a series of ribonucleoprotein immunoprecipitation (RIP) assays, we isolated a pool of mRNAs complexed with HAX1 and/or CCHCR1 proteins. Among the mRNAs complexed with both CCHCR1 and HAX1 proteins, there are Vimentin mRNA, previously described to be bound by HAX1, and CAMP/LL37 mRNA, whose gene product is over-expressed in psoriasis.
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Affiliation(s)
- Cinzia Pisani
- CNR-Institute of Molecular Biology and Pathology, Department of Molecular Medicine, Sapienza University of Rome, Italy.
| | - Annalisa Onori
- CNR-Institute of Molecular Biology and Pathology, Department of Molecular Medicine, Sapienza University of Rome, Italy.
| | - Francesca Gabanella
- CNR-Institute of Molecular Biology and Pathology, Department of Molecular Medicine, Sapienza University of Rome, Italy; CNR-Institute of Biochemistry and Cell Biology, Department of Sense Organs, Sapienza University of Rome, Italy.
| | - Maria Grazia Di Certo
- CNR-Institute of Biochemistry and Cell Biology, Department of Sense Organs, Sapienza University of Rome, Italy.
| | - Claudio Passananti
- CNR-Institute of Molecular Biology and Pathology, Department of Molecular Medicine, Sapienza University of Rome, Italy.
| | - Nicoletta Corbi
- CNR-Institute of Molecular Biology and Pathology, Department of Molecular Medicine, Sapienza University of Rome, Italy.
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5
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Accili E. An ion channel in the company of a transporter. J Gen Physiol 2020; 152:151884. [PMID: 32579683 PMCID: PMC7335010 DOI: 10.1085/jgp.202012590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Affiliation(s)
- Eric Accili
- Department of Cellular and Physiological Sciences, The University of British Columbia, Vancouver, BC, Canada
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6
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Prosdocimi E, Checchetto V, Leanza L. Targeting the Mitochondrial Potassium Channel Kv1.3 to Kill Cancer Cells: Drugs, Strategies, and New Perspectives. SLAS DISCOVERY 2019; 24:882-892. [PMID: 31373829 DOI: 10.1177/2472555219864894] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cancer is the consequence of aberrations in cell growth or cell death. In this scenario, mitochondria and ion channels play a critical role in regard to cell proliferation, malignant angiogenesis, migration, and metastasis. In this review, we focus on Kv1.3 and specifically on mitoKv1.3, which showed an aberrant expression in cancer cells compared with healthy tissues and which is involved in the apoptotic pathway. In recent years, mitoKv1.3 has become an oncological target since its pharmacological modulation has been demonstrated to reduce tumor growth and progression both in vitro and in vivo using preclinical mouse models of different types of tumors.
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Affiliation(s)
| | | | - Luigi Leanza
- Department of Biology, University of Padova, Padova, Italy
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7
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Cleymaet AM, Gallagher SK, Tooker RE, Lipin MY, Renna JM, Sodhi P, Berg D, Hartwick ATE, Berson DM, Vigh J. μ-Opioid Receptor Activation Directly Modulates Intrinsically Photosensitive Retinal Ganglion Cells. Neuroscience 2019; 408:400-417. [PMID: 30981862 PMCID: PMC6604633 DOI: 10.1016/j.neuroscience.2019.04.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 03/12/2019] [Accepted: 04/03/2019] [Indexed: 01/17/2023]
Abstract
Intrinsically photosensitive retinal ganglion cells (ipRGCs) encode light intensity and trigger reflexive responses to changes in environmental illumination. In addition to functioning as photoreceptors, ipRGCs are post-synaptic neurons in the inner retina, and there is increasing evidence that their output can be influenced by retinal neuromodulators. Here we show that opioids can modulate light-evoked ipRGC signaling, and we demonstrate that the M1, M2 and M3 types of ipRGCs are immunoreactive for μ-opioid receptors (MORs) in both mouse and rat. In the rat retina, application of the MOR-selective agonist DAMGO attenuated light-evoked firing ipRGCs in a dose-dependent manner (IC50 < 40 nM), and this effect was reversed or prevented by co-application of the MOR-selective antagonists CTOP or CTAP. Recordings from solitary ipRGCs, enzymatically dissociated from retinas obtained from melanopsin-driven fluorescent reporter mice, confirmed that DAMGO exerts its effect directly through MORs expressed by ipRGCs. Reduced ipRGC excitability occurred via modulation of voltage-gated potassium and calcium currents. These findings suggest a potential new role for endogenous opioids in the mammalian retina and identify a novel site of action-MORs on ipRGCs-through which opioids might exert effects on reflexive responses to environmental light.
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Affiliation(s)
- Allison M Cleymaet
- Dept. of Biomedical Sciences, Colorado State University, Ft. Collins, CO 80523; Dept. of Clinical Sciences, Colorado State University, Ft. Collins, CO 80523
| | - Shannon K Gallagher
- Dept. of Biomedical Sciences, Colorado State University, Ft. Collins, CO 80523
| | - Ryan E Tooker
- Dept. of Biomedical Sciences, Colorado State University, Ft. Collins, CO 80523
| | - Mikhail Y Lipin
- Dept. of Biomedical Sciences, Colorado State University, Ft. Collins, CO 80523
| | - Jordan M Renna
- Dept. of Neuroscience, Brown University, Providence, RI 02912, United States of America
| | - Puneet Sodhi
- College of Optometry, Ohio State University, Columbus, OH 43210, United States of America
| | - Daniel Berg
- Dept. of Neuroscience, Brown University, Providence, RI 02912, United States of America
| | - Andrew T E Hartwick
- College of Optometry, Ohio State University, Columbus, OH 43210, United States of America
| | - David M Berson
- Dept. of Neuroscience, Brown University, Providence, RI 02912, United States of America
| | - Jozsef Vigh
- Dept. of Biomedical Sciences, Colorado State University, Ft. Collins, CO 80523.
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8
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Delgado-Ramírez M, Rodríguez-Menchaca AA. Cytoskeleton disruption affects Kv2.1 channel function and its modulation by PIP 2. J Physiol Sci 2019; 69:513-521. [PMID: 30900190 PMCID: PMC10717730 DOI: 10.1007/s12576-019-00671-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 02/07/2019] [Accepted: 03/07/2019] [Indexed: 11/29/2022]
Abstract
Voltage-gated potassium channels are expressed in a wide variety of excitable and non-excitable cells and regulate numerous cellular functions. The activity of ion channels can be modulated by direct interaction or/and functional coupling with other proteins including auxiliary subunits, scaffold proteins and the cytoskeleton. Here, we evaluated the influence of the actin-based cytoskeleton on the Kv2.1 channel using pharmacological and electrophysiological methods. We found that disruption of the actin-based cytoskeleton by latrunculin B resulted in the regulation of the Kv2.1 inactivation mechanism; it shifted the voltage of half-maximal inactivation toward negative potentials by approximately 15 mV, accelerated the rate of closed-state inactivation, and delayed the recovery rate from inactivation. The actin cytoskeleton stabilizing agent phalloidin prevented the hyperpolarizing shift in the half-maximal inactivation potential when co-applied with latrunculin B. Additionally, PIP2 depletion (a strategy that regulates Kv2.1 inactivation) after cytoskeleton disruption does not regulate further the inactivation of Kv2.1, which suggests that both factors could be regulating the Kv2.1 channel by a common mechanism. In summary, our results suggest a role for the actin-based cytoskeleton in regulating Kv2.1 channels.
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Affiliation(s)
- Mayra Delgado-Ramírez
- Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, Venustiano Carranza #2405, Col. Los Filtros, 78210, San Luis Potosí, SLP, Mexico
| | - Aldo A Rodríguez-Menchaca
- Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, Venustiano Carranza #2405, Col. Los Filtros, 78210, San Luis Potosí, SLP, Mexico.
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9
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Baronas VA, Yang RY, Morales LC, Sipione S, Kurata HT. Slc7a5 regulates Kv1.2 channels and modifies functional outcomes of epilepsy-linked channel mutations. Nat Commun 2018; 9:4417. [PMID: 30356053 PMCID: PMC6200743 DOI: 10.1038/s41467-018-06859-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Accepted: 10/02/2018] [Indexed: 01/25/2023] Open
Abstract
Kv1.2 is a prominent voltage-gated potassium channel that influences action potential generation and propagation in the central nervous system. We explored multi-protein complexes containing Kv1.2 using mass spectrometry followed by screening for effects on Kv1.2. We report that Slc7a5, a neutral amino acid transporter, has a profound impact on Kv1.2. Co-expression with Slc7a5 reduces total Kv1.2 protein, and dramatically hyperpolarizes the voltage-dependence of activation by -47 mV. These effects are attenuated by expression of Slc3a2, a known binding partner of Slc7a5. The profound Slc7a5-mediated current suppression is partly explained by a combination of gating effects including accelerated inactivation and a hyperpolarizing shift of channel activation, causing channels to accumulate in a non-conducting state. Two recently reported Slc7a5 mutations linked to neurodevelopmental delay exhibit a localization defect and have attenuated effects on Kv1.2. In addition, epilepsy-linked gain-of-function Kv1.2 mutants exhibit enhanced sensitivity to Slc7a5.
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Affiliation(s)
- Victoria A Baronas
- Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada
| | - Runying Y Yang
- Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada
| | - Luis Carlos Morales
- Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada
| | - Simonetta Sipione
- Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Harley T Kurata
- Department of Pharmacology, University of Alberta, Edmonton, T6G 2R3, Canada. .,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada. .,Alberta Diabetes Institute, University of Alberta, Edmonton, Canada.
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10
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Voros O, Szilagyi O, Balajthy A, Somodi S, Panyi G, Hajdu P. The C-terminal HRET sequence of Kv1.3 regulates gating rather than targeting of Kv1.3 to the plasma membrane. Sci Rep 2018; 8:5937. [PMID: 29650988 PMCID: PMC5897520 DOI: 10.1038/s41598-018-24159-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 03/08/2018] [Indexed: 12/13/2022] Open
Abstract
Kv1.3 channels are expressed in several cell types including immune cells, such as T lymphocytes. The targeting of Kv1.3 to the plasma membrane is essential for T cell clonal expansion and assumed to be guided by the C-terminus of the channel. Using two point mutants of Kv1.3 with remarkably different features compared to the wild-type Kv1.3 (A413V and H399K having fast inactivation kinetics and tetraethylammonium-insensitivity, respectively) we showed that both Kv1.3 channel variants target to the membrane when the C-terminus was truncated right after the conserved HRET sequence and produce currents identical to those with a full-length C-terminus. The truncation before the HRET sequence (NOHRET channels) resulted in reduced membrane-targeting but non-functional phenotypes. NOHRET channels did not display gating currents, and coexpression with wild-type Kv1.3 did not rescue the NOHRET-A413V phenotype, no heteromeric current was observed. Interestingly, mutants of wild-type Kv1.3 lacking HRET(E) (deletion) or substituted with five alanines for the HRET(E) motif expressed current indistinguishable from the wild-type. These results demonstrate that the C-terminal region of Kv1.3 immediately proximal to the S6 helix is required for the activation gating and conduction, whereas the presence of the distal region of the C-terminus is not exclusively required for trafficking of Kv1.3 to the plasma membrane.
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Affiliation(s)
- Orsolya Voros
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - Orsolya Szilagyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - András Balajthy
- Department of Pediatrics, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - Sándor Somodi
- Department of Internal Medicine, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 1 Egyetem sq., 4032, Hungary. MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, University of Debrecen, 400, Debrecen, Hungary
| | - Péter Hajdu
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary. .,Department of Biophysics and Cell Biology, Faculty of Dentistry, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary.
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11
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Parkinson GT, Chamberlain SEL, Jaafari N, Turvey M, Mellor JR, Hanley JG. Cortactin regulates endo-lysosomal sorting of AMPARs via direct interaction with GluA2 subunit. Sci Rep 2018. [PMID: 29515177 PMCID: PMC5841360 DOI: 10.1038/s41598-018-22542-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
AMPA receptor (AMPAR) trafficking is a key determinant of synaptic strength and synaptic plasticity. Under basal conditions, constitutive trafficking maintains surface AMPARs by internalization into the endosomal system, where the majority are sorted and targeted for recycling back to the plasma membrane. NMDA receptor (NMDAR)-dependent Long-Term Depression (LTD) is characterised by a reduction in synaptic strength, and involves endosomal sorting of AMPARs away from recycling pathways to lysosomes. The mechanisms that determine whether AMPARs are trafficked to lysosomes or to recycling endosomes, especially in response to NMDAR stimulation, are unclear. Here, we define a role for the actin-regulatory protein cortactin as a mediator of AMPAR endosomal sorting by direct interaction with the GluA2 subunit. Disrupting GluA2-cortactin binding in neurons causes the targeting of GluA2/A3-containing receptors to lysosomes and their consequent degradation, resulting in a loss of surface and synaptic GluA2 under basal conditions and an occlusion of subsequent LTD expression. Furthermore, we show that NMDAR stimulation causes a dissociation of endogenous cortactin from GluA2 via tyrosine phosphorylation of cortactin. These results demonstrate that cortactin maintains GluA2/A3 levels by directing receptors away from lysosomes, and that disrupting GluA2-cortactin interactions to target GluA2/A3 to lysosomes is an essential component of LTD expression.
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Affiliation(s)
- Gabrielle T Parkinson
- Centre for Synaptic Plasticity and School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK
| | - Sophie E L Chamberlain
- Centre for Synaptic Plasticity and School of Physiology, Pharmacology & Neuroscience, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK
| | - Nadia Jaafari
- Centre for Synaptic Plasticity and School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK
| | - Matthew Turvey
- Centre for Synaptic Plasticity and School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK
| | - Jack R Mellor
- Centre for Synaptic Plasticity and School of Physiology, Pharmacology & Neuroscience, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK
| | - Jonathan G Hanley
- Centre for Synaptic Plasticity and School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8, 1TD, UK.
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12
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Cortactin: Cell Functions of A Multifaceted Actin-Binding Protein. Trends Cell Biol 2018; 28:79-98. [DOI: 10.1016/j.tcb.2017.10.009] [Citation(s) in RCA: 123] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 10/26/2017] [Accepted: 10/27/2017] [Indexed: 12/30/2022]
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13
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Abstract
Actin remodeling plays an essential role in diverse cellular processes such as cell motility, vesicle trafficking or cytokinesis. The scaffold protein and actin nucleation promoting factor Cortactin is present in virtually all actin-based structures, participating in the formation of branched actin networks. It has been involved in the control of endocytosis, and vesicle trafficking, axon guidance and organization, as well as adhesion, migration and invasion. To migrate and invade through three-dimensional environments, cells have developed specialized actin-based structures called invadosomes, a generic term to designate invadopodia and podosomes. Cortactin has emerged as a critical regulator of invadosome formation, function and disassembly. Underscoring this role, Cortactin is frequently overexpressed in several types of invasive cancers. Herein we will review the roles played by Cortactin in these specific invasive structures.
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Affiliation(s)
- Pauline Jeannot
- CRCT INSERM UMR1037, Université Toulouse III Paul Sabatier , CNRS ERL5294, Toulouse, France.,Cell Signalling Group, Cancer Research UK Manchester Institute, The University of Manchester , Manchester M20 4BX, UK
| | - Arnaud Besson
- CRCT INSERM UMR1037, Université Toulouse III Paul Sabatier , CNRS ERL5294, Toulouse, France.,LBCMCP , Centre de Biologie Intégrative, Université de Toulouse , CNRS, UPS, Toulouse Cedex, France
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14
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Pérez-García MT, Cidad P, López-López JR. The secret life of ion channels: Kv1.3 potassium channels and proliferation. Am J Physiol Cell Physiol 2017; 314:C27-C42. [PMID: 28931540 DOI: 10.1152/ajpcell.00136.2017] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Kv1.3 channels are involved in the switch to proliferation of normally quiescent cells, being implicated in the control of cell cycle in many different cell types and in many different ways. They modulate membrane potential controlling K+ fluxes, sense changes in potential, and interact with many signaling molecules through their intracellular domains. From a mechanistic point of view, we can describe the role of Kv1.3 channels in proliferation with at least three different models. In the "membrane potential model," membrane hyperpolarization resulting from Kv1.3 activation provides the driving force for Ca2+ influx required to activate Ca2+-dependent transcription. This model explains most of the data obtained from several cells from the immune system. In the "voltage sensor model," Kv1.3 channels serve mainly as sensors that transduce electrical signals into biochemical cascades, independently of their effect on membrane potential. Kv1.3-dependent proliferation of vascular smooth muscle cells (VSMCs) could fit this model. Finally, in the "channelosome balance model," the master switch determining proliferation may be related to the control of the Kv1.3 to Kv1.5 ratio, as described in glial cells and also in VSMCs. Since the three mechanisms cannot function independently, these models are obviously not exclusive. Nevertheless, they could be exploited differentially in different cells and tissues. This large functional flexibility of Kv1.3 channels surely gives a new perspective on their functions beyond their elementary role as ion channels, although a conclusive picture of the mechanisms involved in Kv1.3 signaling to proliferation is yet to be reached.
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Affiliation(s)
- M Teresa Pérez-García
- Departamento de Bioquímica y Biología Molecular y Fisiología e Instituto de Biología y Genética Molecular, Universidad de Valladolid y Consejo Superior de Investigaciones Científicas , Valladolid , Spain
| | - Pilar Cidad
- Departamento de Bioquímica y Biología Molecular y Fisiología e Instituto de Biología y Genética Molecular, Universidad de Valladolid y Consejo Superior de Investigaciones Científicas , Valladolid , Spain
| | - José R López-López
- Departamento de Bioquímica y Biología Molecular y Fisiología e Instituto de Biología y Genética Molecular, Universidad de Valladolid y Consejo Superior de Investigaciones Científicas , Valladolid , Spain
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15
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Distribution of Iron Oxide Core-Titanium Dioxide Shell Nanoparticles in VX2 Tumor Bearing Rabbits Introduced by Two Different Delivery Modalities. NANOMATERIALS 2016; 6:nano6080143. [PMID: 28335271 PMCID: PMC5224625 DOI: 10.3390/nano6080143] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 07/10/2016] [Accepted: 07/21/2016] [Indexed: 01/13/2023]
Abstract
This work compares intravenous (IV) versus fluoroscopy-guided transarterial intra-catheter (IC) delivery of iron oxide core-titanium dioxide shell nanoparticles (NPs) in vivo in VX2 model of liver cancer in rabbits. NPs coated with glucose and decorated with a peptide sequence from cortactin were administered to animals with developed VX2 liver cancer. Two hours after NPs delivery tumors, normal liver, kidney, lung and spleen tissues were harvested and used for a series on histological and elemental analysis tests. Quantification of NPs in tissues was done both by bulk inductively coupled plasma mass spectrometry (ICP-MS) analysis and by hard X-ray fluorescence microscopy. Both IV and IC NPs injection are feasible modalities for delivering NPs to VX2 liver tumors with comparable tumor accumulation. It is possible that this is an outcome of the fact that VX2 tumors are highly vascularized and hemorrhagic, and therefore enhanced permeability and retention (EPR) plays the most significant role in accumulation of nanoparticles in tumor tissue. It is, however, interesting to note that IV delivery led to increased sequestration of NPs by spleen and normal liver tissue, while IC delivery lead to more NP positive Kupffer cells. This difference is most likely a direct outcome of blood flow dynamics. Armed with this knowledge about nanoparticle delivery, we plan to test them as radiosensitizers in the future.
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16
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Abella JVG, Way M. Actin'g against the Ball and Chain. Dev Cell 2016; 37:11-12. [PMID: 27046828 DOI: 10.1016/j.devcel.2016.03.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Spinocerebellar ataxia type 13 is a rare autosomal-dominant neurodegenerative disease induced by mutations in the voltage-dependent Kv3.3 potassium channel. Recently in Cell, Zhang et al. (2016) provide new insights into how Arp2/3-dependent actin polymerization modulates both Kv3.3 activity and its ability to stimulate actin polymerization via Hax-1.
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Affiliation(s)
- Jasmine V G Abella
- Cellular Signalling and Cytoskeletal Function Laboratory, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Michael Way
- Cellular Signalling and Cytoskeletal Function Laboratory, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.
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17
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Zhang G, Edmundson M, Telezhkin V, Gu Y, Wei X, Kemp PJ, Song B. The Role of Kv1.2 Channel in Electrotaxis Cell Migration. J Cell Physiol 2015; 231:1375-84. [PMID: 26580832 PMCID: PMC4832312 DOI: 10.1002/jcp.25259] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 11/17/2015] [Indexed: 12/16/2022]
Abstract
Voltage-gated potassium Kv1.2 channels play pivotal role in maintaining of resting membrane potential and, consequently, regulation of cellular excitability of neurons. Endogenously generated electric field (EF) have been proven as an important regulator for cell migration and tissue repair. The mechanisms of ion channel involvement in EF-induced cell responses are extensively studied but largely are poorly understood. In this study we generated three COS-7 clones with different expression levels of Kv1.2 channel, and confirmed their functional variations with patch clamp analysis. Time-lapse imaging analysis showed that EF-induced cell migration response was Kv1.2 channel expression level depended. Inhibition of Kv1.2 channels with charybdotoxin (ChTX) constrained the sensitivity of COS-7 cells to EF stimulation more than their motility. Immunocytochemistry and pull-down analyses demonstrated association of Kv1.2 channels with actin-binding protein cortactin and its re-localization to the cathode-facing membrane at EF stimulation, which confirms the mechanism of EF-induced directional migration. This study displays that Kv1.2 channels represent an important physiological link in EF-induced cell migration. The described mechanism suggests a potential application of EF which may improve therapeutic performance in curing injuries of neuronal and/or cardiac tissue repair, post operational therapy, and various degenerative syndromes.
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Affiliation(s)
- Gaofeng Zhang
- Department of Dermatology, No. 1 Hospital of China Medical University, Shenyang, China.,School of Dentistry, College of Biomedical and Life Sciences, Cardiff University, Cardiff, United Kingdom
| | - Mathew Edmundson
- School of Dentistry, College of Biomedical and Life Sciences, Cardiff University, Cardiff, United Kingdom
| | - Vsevolod Telezhkin
- School of Biosciences, College of Biomedical and Life Sciences, Cardiff University, Cardiff, United Kingdom
| | - Yu Gu
- School of Dentistry, College of Biomedical and Life Sciences, Cardiff University, Cardiff, United Kingdom
| | - Xiaoqing Wei
- School of Dentistry, College of Biomedical and Life Sciences, Cardiff University, Cardiff, United Kingdom
| | - Paul J Kemp
- School of Biosciences, College of Biomedical and Life Sciences, Cardiff University, Cardiff, United Kingdom
| | - Bing Song
- Department of Dermatology, No. 1 Hospital of China Medical University, Shenyang, China.,School of Dentistry, College of Biomedical and Life Sciences, Cardiff University, Cardiff, United Kingdom
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18
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Abstract
In excitable cells, ion channels are frequently challenged by repetitive stimuli, and their responses shape cellular behavior by regulating the duration and termination of bursts of action potentials. We have investigated the behavior of Shaker family voltage-gated potassium (Kv) channels subjected to repetitive stimuli, with a particular focus on Kv1.2. Genetic deletion of this subunit results in complete mortality within 2 weeks of birth in mice, highlighting a critical physiological role for Kv1.2. Kv1.2 channels exhibit a unique property described previously as "prepulse potentiation," in which activation by a depolarizing step facilitates activation in a subsequent pulse. In this study, we demonstrate that this property enables Kv1.2 channels to exhibit use-dependent activation during trains of very brief depolarizations. Also, Kv subunits usually assemble into heteromeric channels in the central nervous system, generating diversity of function and sensitivity to signaling mechanisms. We demonstrate that other Kv1 channel types do not exhibit use-dependent activation, but this property is conferred in heteromeric channel complexes containing even a single Kv1.2 subunit. This regulatory mechanism is observed in mammalian cell lines as well as primary cultures of hippocampal neurons. Our findings illustrate that use-dependent activation is a unique property of Kv1.2 that persists in heteromeric channel complexes and may influence function of hippocampal neurons.
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19
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Hajdu P, Martin GV, Chimote AA, Szilagyi O, Takimoto K, Conforti L. The C-terminus SH3-binding domain of Kv1.3 is required for the actin-mediated immobilization of the channel via cortactin. Mol Biol Cell 2015; 26:1640-51. [PMID: 25739456 PMCID: PMC4436776 DOI: 10.1091/mbc.e14-07-1195] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 02/20/2015] [Indexed: 12/18/2022] Open
Abstract
Polarization of Kv1.3 channels is a necessary step in T-cell activation and motility. Nonetheless, the mechanisms regulating the Kv1.3 channel's membrane movement are not understood. This study provides evidence that cortactin, an actin-binding protein, controls Kv1.3 membrane motility via the channel's SH3 domain. Kv1.3 channels play a pivotal role in the activation and migration of T-lymphocytes. These functions are accompanied by the channels' polarization, which is essential for associated downstream events. However, the mechanisms that govern the membrane movement of Kv1.3 channels remain unclear. F-actin polymerization occurs concomitantly to channel polarization, implicating the actin cytoskeleton in this process. Here we show that cortactin, a factor initiating the actin network, controls the membrane mobilization of Kv1.3 channels. FRAP with EGFP-tagged Kv1.3 channels demonstrates that knocking down cortactin decreases the actin-based immobilization of the channels. Using various deletion and mutation constructs, we show that the SH3 motif of Kv1.3 mediates the channel immobilization. Proximity ligation assays indicate that deletion or mutation of the SH3 motif also disrupts interaction of the channel with cortactin. In T-lymphocytes, the interaction between HS1 (the cortactin homologue) and Kv1.3 occurs at the immune synapse and requires the channel's C-terminal domain. These results show that actin dynamics regulates the membrane motility of Kv1.3 channels. They also provide evidence that the SH3 motif of the channel and cortactin plays key roles in this process.
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Affiliation(s)
- Peter Hajdu
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267 Department of Biophysics and Cell Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - Geoffrey V Martin
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267
| | - Ameet A Chimote
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267
| | - Orsolya Szilagyi
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267 Department of Biophysics and Cell Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - Koichi Takimoto
- Department of Bioengineering and Bioinformatics, Nagaoka University of Technology, Nagaoka 940-2137, Japan
| | - Laura Conforti
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267
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20
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Ma L, Yang F, Zheng J. Application of fluorescence resonance energy transfer in protein studies. J Mol Struct 2014; 1077:87-100. [PMID: 25368432 DOI: 10.1016/j.molstruc.2013.12.071] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Since the physical process of fluorescence resonance energy transfer (FRET) was elucidated more than six decades ago, this peculiar fluorescence phenomenon has turned into a powerful tool for biomedical research due to its compatibility in scale with biological molecules as well as rapid developments in novel fluorophores and optical detection techniques. A wide variety of FRET approaches have been devised, each with its own advantages and drawbacks. Especially in the last decade or so, we are witnessing a flourish of FRET applications in biological investigations, many of which exemplify clever experimental design and rigorous analysis. Here we review the current stage of FRET methods development with the main focus on its applications in protein studies in biological systems, by summarizing the basic components of FRET techniques, most established quantification methods, as well as potential pitfalls, illustrated by example applications.
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Affiliation(s)
- Linlin Ma
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA 95616, USA ; Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Fan Yang
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA 95616, USA
| | - Jie Zheng
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA 95616, USA
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21
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Arcangeli A, Crociani O, Bencini L. Interaction of tumour cells with their microenvironment: ion channels and cell adhesion molecules. A focus on pancreatic cancer. Philos Trans R Soc Lond B Biol Sci 2014; 369:20130101. [PMID: 24493749 DOI: 10.1098/rstb.2013.0101] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Cancer must be viewed as a 'tissue', constituted of both transformed cells and a heterogeneous microenvironment, the 'tumour microenvironment' (TME). The TME undergoes a complex remodelling during the course of multistep tumourigenesis, hence strongly contributing to tumour progression. Ion channels and transporters (ICTs), being expressed on both tumour cells and in the different cellular components of the TME, are in a strategic position to sense and mediate signals arising from the TME. Often, this transmission is mediated by integrin adhesion receptors, which are the main cellular receptors capable of mediating cell-to-cell and cell-to-matrix bidirectional signalling. Integrins can often operate in conjunction with ICT because they can behave as functional partners of ICT proteins. The role of integrin receptors in the crosstalk between tumour cells and the TME is particularly relevant in the context of pancreatic cancer (PC), characterized by an overwhelming TME which actively contributes to therapy resistance. We discuss the possibility that this occurs through integrins and ICTs, which could be exploited as targets to overcome chemoresistance in PC.
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Affiliation(s)
- Annarosa Arcangeli
- Department of Experimental and Clinical Medicine, Section of Internal Medicine, University of Florence, , Viale G.B. Morgagni, 50, 50134 Firenze, Italy
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22
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Abstract
Potassium channels are transmembrane proteins that selectively facilitate the flow of potassium ions down an electrochemical gradient. These molecules have been studied in great detail in the context of cell excitability, but their roles in less cell type-specific functions, such as cell proliferation, angiogenesis or cell migration, have only recently been assessed. Moreover, the importance of these channels for tumour biology has become evident. This, coupled with the fact that they are accessible proteins and that their pharmacology is well characterized, has increased the interest in investigating potassium channels as therapeutic targets in cancer patients.
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Affiliation(s)
- Luis A Pardo
- Oncophysiology Group, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
| | - Walter Stühmer
- Department of Molecular Biology of Neuronal Signals, Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
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23
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Stock C, Ludwig FT, Hanley PJ, Schwab A. Roles of ion transport in control of cell motility. Compr Physiol 2013; 3:59-119. [PMID: 23720281 DOI: 10.1002/cphy.c110056] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cell motility is an essential feature of life. It is essential for reproduction, propagation, embryonic development, and healing processes such as wound closure and a successful immune defense. If out of control, cell motility can become life-threatening as, for example, in metastasis or autoimmune diseases. Regardless of whether ciliary/flagellar or amoeboid movement, controlled motility always requires a concerted action of ion channels and transporters, cytoskeletal elements, and signaling cascades. Ion transport across the plasma membrane contributes to cell motility by affecting the membrane potential and voltage-sensitive ion channels, by inducing local volume changes with the help of aquaporins and by modulating cytosolic Ca(2+) and H(+) concentrations. Voltage-sensitive ion channels serve as voltage detectors in electric fields thus enabling galvanotaxis; local swelling facilitates the outgrowth of protrusions at the leading edge while local shrinkage accompanies the retraction of the cell rear; the cytosolic Ca(2+) concentration exerts its main effect on cytoskeletal dynamics via motor proteins such as myosin or dynein; and both, the intracellular and the extracellular H(+) concentration modulate cell migration and adhesion by tuning the activity of enzymes and signaling molecules in the cytosol as well as the activation state of adhesion molecules at the cell surface. In addition to the actual process of ion transport, both, channels and transporters contribute to cell migration by being part of focal adhesion complexes and/or physically interacting with components of the cytoskeleton. The present article provides an overview of how the numerous ion-transport mechanisms contribute to the various modes of cell motility.
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Affiliation(s)
- Christian Stock
- Institute of Physiology II, University of Münster, Münster, Germany.
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24
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Girault A, Brochiero E. Evidence of K+ channel function in epithelial cell migration, proliferation, and repair. Am J Physiol Cell Physiol 2013; 306:C307-19. [PMID: 24196531 DOI: 10.1152/ajpcell.00226.2013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Efficient repair of epithelial tissue, which is frequently exposed to insults, is necessary to maintain its functional integrity. It is therefore necessary to better understand the biological and molecular determinants of tissue regeneration and to develop new strategies to promote epithelial repair. Interestingly, a growing body of evidence indicates that many members of the large and widely expressed family of K(+) channels are involved in regulation of cell migration and proliferation, key processes of epithelial repair. First, we briefly summarize the complex mechanisms, including cell migration, proliferation, and differentiation, engaged after epithelial injury. We then present evidence implicating K(+) channels in the regulation of these key repair processes. We also describe the mechanisms whereby K(+) channels may control epithelial repair processes. In particular, changes in membrane potential, K(+) concentration, cell volume, intracellular Ca(2+), and signaling pathways following modulation of K(+) channel activity, as well as physical interaction of K(+) channels with the cytoskeleton or integrins are presented. Finally, we discuss the challenges to efficient, specific, and safe targeting of K(+) channels for therapeutic applications to improve epithelial repair in vivo.
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Affiliation(s)
- Alban Girault
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montreal, Quebec, Canada; and
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25
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Vacher H, Trimmer JS. Trafficking mechanisms underlying neuronal voltage-gated ion channel localization at the axon initial segment. Epilepsia 2013; 53 Suppl 9:21-31. [PMID: 23216576 DOI: 10.1111/epi.12032] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Voltage-gated ion channels are diverse and fundamental determinants of neuronal intrinsic excitability. Voltage-gated K(+) (Kv) and Na(+) (Nav) channels play complex yet fundamentally important roles in determining intrinsic excitability. The Kv and Nav channels located at the axon initial segment (AIS) play a unique and especially important role in generating neuronal output in the form of anterograde axonal and backpropagating action potentials. Aberrant intrinsic excitability in individual neurons within networks contributes to synchronous neuronal activity leading to seizures. Mutations in ion channel genes give rise to a variety of seizure-related "channelopathies," and many of the ion channel subunits associated with epilepsy mutations are localized at the AIS, making this a hotspot for epileptogenesis. Here we review the cellular mechanisms that underlie the trafficking of Kv and Nav channels found at the AIS, and how Kv and Nav channel mutations associated with epilepsy can alter these processes.
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Affiliation(s)
- Helene Vacher
- CRN2M CNRS UMR7286, Aix-Marseille University, Marseille, France
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26
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Herrmann S, Ninkovic M, Kohl T, Lörinczi É, Pardo LA. Cortactin controls surface expression of the voltage-gated potassium channel K(V)10.1. J Biol Chem 2012; 287:44151-63. [PMID: 23144454 PMCID: PMC3531731 DOI: 10.1074/jbc.m112.372540] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
KV10.1 is a voltage-gated potassium channel aberrantly expressed in many cases of cancer, and participates in cancer initiation and tumor progression. Its action as an oncoprotein can be inhibited by a functional monoclonal antibody, indicating a role for channels located at the plasma membrane, accessible to the antibody. Cortactin is an actin-interacting protein implicated in cytoskeletal architecture and often amplified in several types of cancer. In this study, we describe a physical and functional interaction between cortactin and KV10.1. Binding of these two proteins occurs between the C terminus of KV10.1 and the proline-rich domain of cortactin, regions targeted by many post-translational modifications. This interaction is specific for KV10.1 and does not occur with KV10.2. Cortactin controls the abundance of KV10.1 at the plasma membrane and is required for functional expression of KV10.1 channels.
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Affiliation(s)
- Solveig Herrmann
- Oncophysiology Group, Max-Planck Institute of Experimental Medicine, Hermann-Rein-Str. 3, 37075 Göttingen, Germany
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27
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Cellular mechanisms and behavioral consequences of Kv1.2 regulation in the rat cerebellum. J Neurosci 2012; 32:9228-37. [PMID: 22764231 DOI: 10.1523/jneurosci.6504-11.2012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The potassium channel Kv1.2 α-subunit is expressed in cerebellar Purkinje cell (PC) dendrites where its pharmacological inhibition increases excitability (Khavandgar et al., 2005). Kv1.2 is also expressed in cerebellar basket cell (BC) axon terminals (Sheng et al., 1994), where its blockade increases BC inhibition of PCs (Southan and Robertson, 1998a). Secretin receptors are also expressed both in PC dendrites and BC axon terminals (for review, see (Yuan et al., 2011). The effect of secretin on PC excitability is not yet known, but, like Kv1.2 inhibitors, secretin potently increases inhibitory input to PCs (Yung et al., 2001). This suggests secretin may act in part by suppressing Kv1.2. Receptor-mediated endocytosis is a mechanism of Kv1.2 suppression (Nesti et al., 2004). This process can be regulated by protein kinase A (PKA) (Connors et al., 2008). Since secretin receptors activate PKA (Wessels-Reiker et al., 1993), we tested the hypothesis that secretin regulates Kv1.2 trafficking in the cerebellum. Using cell-surface protein biotinylation of rat cerebellar slices, we found secretin decreased cell-surface Kv1.2 levels by modulating Kv1.2 endocytic trafficking. This effect was mimicked by activating adenylate cyclase (AC) with forskolin, and was blocked by pharmacological inhibitors of AC or PKA. Imaging studies identified the BC axon terminal and PC dendrites as loci of AC-dependent Kv1.2 trafficking. The physiological significance of secretin-regulated Kv1.2 endocytosis is supported by our finding that infusion into the cerebellar cortex of either the Kv1.2 inhibitor tityustoxin-Kα, or of the Kv1.2 regulator secretin, significantly enhances acquisition of eyeblink conditioning in rats.
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28
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Huang Y, Biswas C, Klos Dehring DA, Sriram U, Williamson EK, Li S, Clarke F, Gallucci S, Argon Y, Burkhardt JK. The actin regulatory protein HS1 is required for antigen uptake and presentation by dendritic cells. THE JOURNAL OF IMMUNOLOGY 2011; 187:5952-63. [PMID: 22031761 DOI: 10.4049/jimmunol.1100870] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The hematopoietic actin regulatory protein hematopoietic lineage cell-specific protein 1 (HS1) is required for cell spreading and signaling in lymphocytes, but the scope of HS1 function in Ag presentation has not been addressed. We show that dendritic cells (DCs) from HS1(-/-) mice differentiate normally and display normal LPS-induced upregulation of surface markers and cytokines. Consistent with their normal expression of MHC and costimulatory molecules, HS1(-/-) DCs present OVA peptide efficiently to CD4(+) T cells. However, presentation of OVA protein is defective. Similarly, MHC class I-dependent presentation of VSV8 peptide to CD8(+) T cells occurs normally, but cross-presentation of GRP94/VSV8 complexes is defective. Analysis of Ag uptake pathways shows that HS1 is required for receptor-mediated endocytosis, but not for phagocytosis or macropinocytosis. HS1 interacts with dynamin 2, a protein involved in scission of endocytic vesicles. However, HS1(-/-) DCs showed decreased numbers of endocytic invaginations, whereas dynamin-inhibited cells showed accumulation of these endocytic intermediates. Taken together, these studies show that HS1 promotes an early step in the endocytic pathway that is required for efficient Ag presentation of exogenous Ag by DCs.
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Affiliation(s)
- Yanping Huang
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia and Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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29
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Diverse roles for auxiliary subunits in phosphorylation-dependent regulation of mammalian brain voltage-gated potassium channels. Pflugers Arch 2011; 462:631-43. [PMID: 21822597 DOI: 10.1007/s00424-011-1004-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 07/22/2011] [Accepted: 07/22/2011] [Indexed: 10/17/2022]
Abstract
Voltage-gated ion channels are a diverse family of signaling proteins that mediate rapid electrical signaling events. Among these, voltage-gated potassium or Kv channels are the most diverse partly due to the large number of principal (or α) subunits and auxiliary subunits that can assemble in different combinations to generate Kv channel complexes with distinct structures and functions. The diversity of Kv channels underlies much of the variability in the active properties between different mammalian central neurons and the dynamic changes that lead to experience-dependent plasticity in intrinsic excitability. Recent studies have revealed that Kv channel α subunits and auxiliary subunits are extensively phosphorylated, contributing to additional structural and functional diversity. Here, we highlight recent studies that show that auxiliary subunits exert some of their profound effects on dendritic Kv4 and axonal Kv1 channels through phosphorylation-dependent mechanisms, either due to phosphorylation on the auxiliary subunit itself or by influencing the extent and/or impact of α subunit phosphorylation. The complex effects of auxiliary subunits and phosphorylation provide a potent mechanism to generate additional diversity in the structure and function of Kv4 and Kv1 channels, as well as allowing for dynamic reversible regulation of these important ion channels.
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30
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Ilatovskaya DV, Pavlov TS, Levchenko V, Negulyaev YA, Staruschenko A. Cortical actin binding protein cortactin mediates ENaC activity via Arp2/3 complex. FASEB J 2011; 25:2688-99. [PMID: 21536685 DOI: 10.1096/fj.10-167262] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Epithelial Na(+) channel (ENaC) activity is regulated, in part, by the cortical cytoskeleton. Here we demonstrate that cortactin is highly expressed in the kidney cortex and polarized epithelial cells, and is localized to the cortical collecting duct. Coexpression of cortactin with ENaC decreases ENaC activity, as measured in patch-clamp experiments. Biotinylation experiments and single-channel analysis reveal that cortactin decreases ENaC activity via affecting channel open probability (P(o)). Knockdown of cortactin in mpkCCD(c14) principal cells results in an increase in ENaC activity and sodium reabsorption. Coimmunoprecipitation analysis shows direct interactions between cortactin and all three ENaC subunits in cultured and native cells. To address the question of what mechanism underlies the action of cortactin on ENaC activity, we assayed the effects of various mutants of cortactin. The data show that only a cortactin mutant unable to bind Arp2/3 complex does not influence ENaC activity. Furthermore, inhibitor of the Arp2/3 complex CK-0944666 precludes the effect of cortactin. Depolymerization of the actin microfilaments and inhibition of the Arp2/3 complex does not result in the loss of association between ENaC and cortactin. Thus, these results indicate that cortactin is functionally important for ENaC activity and that Arp2/3 complex is involved in this mechanism.
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Affiliation(s)
- Daria V Ilatovskaya
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA
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31
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Cheng L, Yung A, Covarrubias M, Radice GL. Cortactin is required for N-cadherin regulation of Kv1.5 channel function. J Biol Chem 2011; 286:20478-89. [PMID: 21507952 DOI: 10.1074/jbc.m111.218560] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The intercalated disc serves as an organizing center for various cell surface components at the termini of the cardiomyocyte, thus ensuring proper mechanoelectrical coupling throughout the myocardium. The cell adhesion molecule, N-cadherin, is an essential component of the intercalated disc. Cardiac-specific deletion of N-cadherin leads to abnormal electrical conduction and sudden arrhythmic death in mice. The mechanisms linking the loss of N-cadherin in the heart and spontaneous malignant ventricular arrhythmias are poorly understood. To investigate whether ion channel remodeling contributes to arrhythmogenesis in N-cadherin conditional knock-out (N-cad CKO) mice, cardiac myocyte excitability and voltage-gated potassium channel (Kv), as well as inwardly rectifying K(+) channel remodeling, were investigated in N-cad CKO cardiomyocytes by whole cell patch clamp recordings. Action potential duration was prolonged in N-cad CKO ventricle myocytes compared with wild type. Relative to wild type, I(K,slow) density was significantly reduced consistent with decreased expression of Kv1.5 and Kv accessory protein, Kcne2, in the N-cad CKO myocytes. The decreased Kv1.5/Kcne2 expression correlated with disruption of the actin cytoskeleton and reduced cortactin at the sarcolemma. Biochemical experiments revealed that cortactin co-immunoprecipitates with Kv1.5. Finally, cortactin was required for N-cadherin-mediated enhancement of Kv1.5 channel activity in a heterologous expression system. Our results demonstrate a novel mechanistic link among the cell adhesion molecule, N-cadherin, the actin-binding scaffold protein, cortactin, and Kv channel remodeling in the heart. These data suggest that in addition to gap junction remodeling, aberrant Kv1.5 channel function contributes to the arrhythmogenic phenotype in N-cad CKO mice.
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Affiliation(s)
- Lan Cheng
- Center for Translational Medicine, Department of Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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Fulton S, Thibault D, Mendez JA, Lahaie N, Tirotta E, Borrelli E, Bouvier M, Tempel BL, Trudeau LE. Contribution of Kv1.2 voltage-gated potassium channel to D2 autoreceptor regulation of axonal dopamine overflow. J Biol Chem 2011; 286:9360-72. [PMID: 21233214 DOI: 10.1074/jbc.m110.153262] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Impairments in axonal dopamine release are associated with neurological disorders such as schizophrenia and attention deficit hyperactivity disorder and pathophysiological conditions promoting drug abuse and obesity. The D2 dopamine autoreceptor (D2-AR) exerts tight regulatory control of axonal dopamine (DA) release through a mechanism suggested to involve K(+) channels. To evaluate the contribution of Kv1 voltage-gated potassium channels of the Shaker gene family to the regulation of axonal DA release by the D2-AR, the present study employed expression analyses, real time measurements of striatal DA overflow, K(+) current measurements and immunoprecipitation assays. Kv1.1, -1.2, -1.3, and -1.6 mRNA and protein were detected in midbrain DA neurons purified by fluorescence-activated cell sorting and in primary DA neuron cultures. In addition, Kv1.1, -1.2, and -1.6 were localized to DA axonal processes in the dorsal striatum. By means of fast scan cyclic voltammetry in striatal slice preparations, we found that the inhibition of stimulation-evoked DA overflow by a D2 agonist was attenuated by Kv1.1, -1.2, and -1.6 toxin blockers. A particular role for the Kv1.2 subunit in the process whereby axonal D2-AR inhibits DA overflow was established with the use of a selective Kv1.2 blocker and Kv1.2 knock-out mice. Moreover, we demonstrate the ability of D2-AR activation to increase Kv1.2 currents in co-transfected cells and its reliance on Gβγ subunit signaling along with the physical coupling of D2-AR and Kv1.2-containing channels in striatal tissue. These findings underline the contribution of Kv1.2 in the regulation of nigrostriatal DA release by the D2-AR and thereby offer a novel mechanism by which DA release is regulated.
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Affiliation(s)
- Stephanie Fulton
- Department of Pharmacology and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Quebec H3C 3J7, Canada
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Bernstein BW, Maloney MT, Bamburg JR. Actin and Diseases of the Nervous System. ADVANCES IN NEUROBIOLOGY 2011; 5:201-234. [PMID: 35547659 PMCID: PMC9088176 DOI: 10.1007/978-1-4419-7368-9_11] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Abnormal regulation of the actin cytoskeleton results in several pathological conditions affecting primarily the nervous system. Those of genetic origin arise during development, but others manifest later in life. Actin regulation is also affected profoundly by environmental factors that can have sustained consequences for the nervous system. Those consequences follow from the fact that the actin cytoskeleton is essential for a multitude of cell biological functions ranging from neuronal migration in cortical development and dendritic spine formation to NMDA receptor activity in learning and alcoholism. Improper regulation of actin, causing aggregation, can contribute to the neurodegeneration of amyloidopathies, such as Down's syndrome and Alzheimer's disease. Much progress has been made in understanding the molecular basis of these diseases.
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Affiliation(s)
- Barbara W Bernstein
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523
| | - Michael T Maloney
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523
| | - James R Bamburg
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523
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Integrins and ion channels in cell migration: implications for neuronal development, wound healing and metastatic spread. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 674:107-23. [PMID: 20549944 DOI: 10.1007/978-1-4419-6066-5_10] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cells migration is necessary for proper embryonic development and adult tissue remodeling. Its mechanisms determine the physiopathology of processes such as neuronal targeting, inflammation, wound healing and metastatic spread. Crawling of cells onto solid surfaces requires a controlled sequence of cell protrusions and retractions that mainly depends on sophisticated regulation of the actin cytoskeleton, although the contribution of microtubules should not be neglected. This process is triggered and modulated by a combination of diffusible and fixed environmental signals. External cues are sensed and integrated by membrane receptors, including integrins, which transduce these signals into cellular signaling pathways, often centered on the small GTPase proteins belonging to the Rho family. These pathways regulate the coordinated cytoskeletal rearrangements necessary for proper timing of adhesion, contraction and detachement at the front and rear side of cells finding their way through the extracellular spaces. The overall process involves continuous modulation of cell motility, shape and volume, in which ion channels play major roles. In particular, Ca2+ signals have both global and local regulatory effects on cell motility, because they target the contractile proteins as well as many regulatory proteins. After reviewing the fundamental mechanisms of eukaryotic cell migration onto solid substrates, we briefly describe how integrin receptors and ion channels are involved in cell movement. We next examine a few processes in which these mechanisms have been studied in depth. We thus illustrate how integrins and K+ channels control cell volume and migration, how intracellular Ca2+ homeostasis affects the motility of neuronal growth cones and what is known about the ion channel roles in epithelial cell migration. These mechanisms are implicated in a variety of pathological processes, such as the disruption of neural circuits and wound healing. Finally, we describe the interaction between neoplastic cells and their local environment and how derangement of adhesion can lead to metastatic spread. It is likely that the cellular mechanisms controlled by integrin receptors, ion channels or both participate in the entire metastatic process. Until now, however, evidence is limited to a few steps of the metastatic cascade, such as brain tumor invasiveness.
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New insights into the regulation of ion channels by integrins. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 279:135-90. [PMID: 20797679 DOI: 10.1016/s1937-6448(10)79005-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
By controlling cell adhesion to the extracellular matrix, integrin receptors regulate processes as diverse as cell migration, proliferation, differentiation, apoptosis, and synaptic stability. Because the underlying mechanisms are generally accompanied by changes in transmembrane ion flow, a complex interplay occurs between integrins, ion channels, and other membrane transporters. This reciprocal interaction regulates bidirectional signal transduction across the cell surface and may take place at all levels of control, from transcription to direct conformational coupling. In particular, it is becoming increasingly clear that integrin receptors form macromolecular complexes with ion channels. Besides contributing to the membrane localization of the channel protein, the integrin/channel complex can regulate a variety of downstream signaling pathways, centered on regulatory proteins like tyrosine kinases and small GTPases. In turn, the channel protein usually controls integrin activation and expression. We review some recent advances in the field, with special emphasis on hematology and neuroscience. Some oncological implications are also discussed.
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36
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Masi A, Cicchi R, Carloni A, Pavone FS, Arcangeli A. Optical methods in the study of protein-protein interactions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 674:33-42. [PMID: 20549938 DOI: 10.1007/978-1-4419-6066-5_4] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Förster (or Fluorescence) resonance energy transfer (FRET) is a physical process in which energy is transferred nonradiatively from an excited fluorophore, serving as a donor, to another chromophore (acceptor). Among the techniques related to fluorescence microscopy, FRET is unique in providing signals sensitive to intra- and intermolecular distances in the 1-10 nm range. Because of its potency, FRET is increasingly used to visualize and quantify the dynamics of protein-protein interaction in living cells, with high spatio-temporal resolution. Here we describe the physical bases of FRET, detailing the principal methods applied: (1) measurement of signal intensity and (2) analysis of fluorescence lifetime (FLIM). Although several technical complications must be carefully considered, both methods can be applied fruitfully to specific fields. For example, FRET based on intensity detection is more suitable to follow biological phenomena at a finely tuned spatial and temporal scale. Furthermore, a specific fluorescence signal occurring close to the plasma membrane (< or = 100 nm) can be obtained using a total internal reflection fluorescence (TIRF) microscopy system. When performing FRET experiments, care must be also taken to the method chosen for labeling interacting proteins. Two principal tools can be applied: (1) fluorophore tagged antibodies; (2) recombinant fluorescent fusion proteins. The latter method essentially takes advantage of the discovery and use of spontaneously fluorescent proteins, like the green fluorescent protein (GFP). Until now, FRET has been widely used to analyze the structural characteristics of several proteins, including integrins and ion channels. More recently, this method has been applied to clarify the interaction dynamics of these classes of membrane proteins with cytosolic signaling proteins. We report two examples in which the interaction dynamics between integrins and ion channels have been studied with FRET methods. Using fluorescent antibodies and applying FRET-FLIM, the direct interaction of beta1 integrin with the receptor for Epidermal Growth Factor (EGF-R) has been proved in living endothelial cells. A different approach, based on TIRFM measurement of the FRET intensity of fluorescently labeled recombinant proteins, suggests that a direct interaction also occurs between integrins and the ether-a-go-go-related-gene 1 (hERG1) K+ channel.
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Affiliation(s)
- Alessio Masi
- Department of Experimental Pathology and Oncology, University of Florence, Italy
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Stirling L, Williams MR, Morielli AD. Dual roles for RHOA/RHO-kinase in the regulated trafficking of a voltage-sensitive potassium channel. Mol Biol Cell 2009; 20:2991-3002. [PMID: 19403695 DOI: 10.1091/mbc.e08-10-1074] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Kv1.2 is a member of the Shaker family of voltage-sensitive potassium channels and contributes to regulation of membrane excitability. The electrophysiological activity of Kv1.2 undergoes tyrosine kinase-dependent suppression in a process involving RhoA. We report that RhoA elicits suppression of Kv1.2 ionic current by modulating channel endocytosis. This occurs through two distinct pathways, one clathrin-dependent and the other cholesterol-dependent. Activation of Rho kinase (ROCK) via the lysophosphatidic acid (LPA) receptor elicits clathrin-dependent Kv1.2 endocytosis and consequent attenuation of its ionic current. LPA-induced channel endocytosis is blocked by the ROCK inhibitor Y27632 or by clathrin RNA interference. In contrast, steady-state endocytosis of Kv1.2 in unstimulated cells is cholesterol dependent. Inhibition of basal ROCK signaling with Y27632 increased surface Kv1.2, an effect that persists in the presence of clathrin small interfering RNA and that is not additive to the increase in surface channel levels elicited by the cholesterol sequestering drug filipin. Temperature block experiments show that ROCK affects cholesterol-dependent trafficking by modulating the recycling of endocytosed channel back to the plasma membrane. Both receptor-stimulated and steady-state Kv1.2 trafficking modulated by RhoA/ROCK required the activation of dynamin as well as the ROCK effector Lim-kinase, indicating a key role for actin remodeling in RhoA-dependent Kv1.2 regulation.
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Affiliation(s)
- Lee Stirling
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05405, USA
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38
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Klemmer P, Smit AB, Li KW. Proteomics analysis of immuno-precipitated synaptic protein complexes. J Proteomics 2008; 72:82-90. [PMID: 19022416 DOI: 10.1016/j.jprot.2008.10.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 10/21/2008] [Accepted: 10/23/2008] [Indexed: 11/18/2022]
Abstract
Synapses are key neuronal elements of the brain. They are responsible for transmission, integration, and storage of information between nerve cells. A synapse is considered as the most complex cellular organelle consisting of approximately 1500 of proteins that are interacting in an activity dependent manner. We have initiated a series of immuno-precipitation experiments in conjunction with LC-MS/MS analysis in order to gain better insight into the organization of the synapse. In particular, we focused on proteins that have been implicated previously in the process of neuroplasticity, i.e., the glutamate receptor (GluR2), scaffolding proteins (PSD-95 and CASK), voltage gated potassium (KCNQ2 and Kv4.2) and calcium (CaV beta4) channel subunits, the signalling protein (GIT1) and synaptic vesicle protein (synaptophysin). This study confirms the previous reported protein-protein interactions and furthermore detects novel interactors. In conjunction with the literature reported protein-protein interaction a simple synaptic protein interactome was constructed. This model implicates the potential interaction of distinct protein complexes, and the engagement of single proteins, especially the scaffolding proteins, in multiple protein complexes.
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Affiliation(s)
- P Klemmer
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam,De Boelelaan 1085, 1081 Amsterdam, The Netherlands
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Schwab A, Hanley P, Fabian A, Stock C. Potassium Channels Keep Mobile Cells on the Go. Physiology (Bethesda) 2008; 23:212-20. [DOI: 10.1152/physiol.00003.2008] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Cell motility is a prerequisite for the creation of new life, and it is required for maintaining the integrity of an organism. Under pathological conditions, “too much” motility may cause premature death. Studies over the past few years have revealed that ion channels are essential for cell motility. This review highlights the importance of K+ channels in regulating cell motility.
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Affiliation(s)
| | - Peter Hanley
- Institut für Physiologie II, Universität Münster, Germany
| | - Anke Fabian
- Institut für Physiologie II, Universität Münster, Germany
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40
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McKeown L, Swanton L, Robinson P, Jones OT. Surface expression and distribution of voltage-gated potassium channels in neurons (Review). Mol Membr Biol 2008; 25:332-43. [PMID: 18446619 DOI: 10.1080/09687680801992470] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The last decade has witnessed an exponential increase in interest in one of the great mysteries of nerve cell biology: Specifically, how do neurons know where to place the ion channels that control their excitability? Many of the most important insights have been gleaned from studies on the voltage-gated potassium channels (Kvs) which underlie the shape, duration and frequency of action potentials. In this review, we gather recent evidence on the expression, trafficking and maintenance mechanisms which control the surface density of Kvs in different subcellular compartments of neurons and how these may be regulated to control cell excitability.
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Affiliation(s)
- Lynn McKeown
- Faculty of Life Sciences, The University of Manchester, Manchester, UK
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41
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Connors EC, Ballif BA, Morielli AD. Homeostatic regulation of Kv1.2 potassium channel trafficking by cyclic AMP. J Biol Chem 2007; 283:3445-3453. [PMID: 18003609 DOI: 10.1074/jbc.m708875200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Shaker family potassium channel, Kv1.2, is a key determinant of membrane excitability in neurons and cardiovascular tissue. Kv1.2 is subject to multiple forms of regulation and therefore integrates cellular signals involved in the homeostasis of excitability. The cyclic AMP/protein kinase A (PKA) pathway enhances Kv1.2 ionic current; however, the mechanisms for this are not fully known. Here we show that cAMP maintains Kv1.2 homeostasis through opposing effects on channel trafficking. We found that Kv1.2 is regulated by two distinct cAMP pathways, one PKA-dependent and the other PKA-independent. PKA inhibitors elevate Kv1.2 surface levels, suggesting that basal levels of cAMP control steady-state turnover of the channel. Elevation of cAMP above basal levels also increases the amount of Kv1.2 at the cell surface. This effect is not blocked by PKA inhibitors, but is blocked by inhibition of Kv1.2 endocytosis. We conclude that Kv1.2 levels at the cell surface are kept in dynamic balance by opposing effects of cAMP.
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Affiliation(s)
- Emilee C Connors
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont 05405
| | - Bryan A Ballif
- Department of Biology, University of Vermont, Burlington, Vermont 05405
| | - Anthony D Morielli
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont 05405.
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