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Cozzolino M, Panyi G. Intracellular acidity impedes KCa3.1 activation by Riluzole and SKA-31. Front Pharmacol 2024; 15:1380655. [PMID: 38638868 PMCID: PMC11024243 DOI: 10.3389/fphar.2024.1380655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Accepted: 03/05/2024] [Indexed: 04/20/2024] Open
Abstract
Background The unique microenvironment in tumors inhibits the normal functioning of tumor-infiltrating lymphocytes, leading to immune evasion and cancer progression. Over-activation of KCa3.1 using positive modulators has been proposed to rescue the anti-tumor response. One of the key characteristics of the tumor microenvironment is extracellular acidity. Herein, we analyzed how intra- and extracellular pH affects K+ currents through KCa3.1 and if the potency of two of its positive modulators, Riluzole and SKA-31, is pH sensitive. Methods Whole-cell patch-clamp was used to measure KCa3.1 currents either in activated human peripheral lymphocytes or in CHO cells transiently transfected with either the H192A mutant or wild-type hKCa3.1 in combination with T79D-Calmodulin, or with KCa2.2. Results We found that changes in the intra- and extracellular pH minimally influenced the KCa3.1-mediated K+ current. Extracellular pH, in the range of 6.0-8.0, does not interfere with the capacity of Riluzole and SKA-31 to robustly activate the K+ currents through KCa3.1. Contrariwise, an acidic intracellular solution causes a slow, but irreversible loss of potency of both the activators. Using different protocols of perfusion and depolarization we demonstrated that the loss of potency is strictly time and pH-dependent and that this peculiar effect can be observed with a structurally similar channel KCa2.2. While two different point mutations of both KCa3.1 (H192A) and its associated protein Calmodulin (T79D) do not limit the effect of acidity, increasing the cytosolic Ca2+ concentration to saturating levels eliminated the loss-of-potency phenotype. Conclusion Based on our data we conclude that KCa3.1 currents are not sensitive the either the intracellular or the extracellular pH in the physiological and pathophysiological range. However, intracellular acidosis in T cells residing in the tumor microenvironment could hinder the potentiating effect of KCa3.1 positive modulators administered to boost their activity. Further research is warranted both to clarify the molecular interactions between the modulators and KCa3.1 at different intracellular pH conditions and to define whether this loss of potency can be observed in cancer models as well.
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Affiliation(s)
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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2
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Ong ST, Tyagi A, Chandy KG, Bhushan S. Mechanisms Underlying C-type Inactivation in Kv Channels: Lessons From Structures of Human Kv1.3 and Fly Shaker-IR Channels. Front Pharmacol 2022; 13:924289. [PMID: 35833027 PMCID: PMC9271579 DOI: 10.3389/fphar.2022.924289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 06/06/2022] [Indexed: 11/13/2022] Open
Abstract
Voltage-gated potassium (Kv) channels modulate the function of electrically-excitable and non-excitable cells by using several types of “gates” to regulate ion flow through the channels. An important gating mechanism, C-type inactivation, limits ion flow by transitioning Kv channels into a non-conducting inactivated state. Here, we highlight two recent papers, one on the human Kv1.3 channel and the second on the Drosophila Shaker Kv channel, that combined cryogenic electron microscopy and molecular dynamics simulation to define mechanisms underlying C-type inactivation. In both channels, the transition to the non-conducting inactivated conformation begins with the rupture of an intra-subunit hydrogen bond that fastens the selectivity filter to the pore helix. The freed filter swings outwards and gets tethered to an external residue. As a result, the extracellular end of the selectivity filter dilates and K+ permeation through the pore is impaired. Recovery from inactivation may entail a reversal of this process. Such a reversal, at least partially, is induced by the peptide dalazatide. Binding of dalazatide to external residues in Kv1.3 frees the filter to swing inwards. The extracellular end of the selectivity filter narrows allowing K+ to move in single file through the pore typical of conventional knock-on conduction. Inter-subunit hydrogen bonds that stabilize the outer pore in the dalazatide-bound structure are equivalent to those in open-conducting conformations of Kv channels. However, the intra-subunit bond that fastens the filter to the pore-helix is absent, suggesting an incomplete reversal of the process. These mechanisms define how Kv channels self-regulate the flow of K+ by changing the conformation of the selectivity filter.
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Affiliation(s)
- Seow Theng Ong
- LKCMedicine-ICESing Ion Channel Platform, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Anu Tyagi
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- Singapore and Nanyang Institute of Structural Biology, Nanyang Technological University, Singapore, Singapore
| | - K. George Chandy
- LKCMedicine-ICESing Ion Channel Platform, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
- *Correspondence: K. George Chandy, ; Shashi Bhushan,
| | - Shashi Bhushan
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- Singapore and Nanyang Institute of Structural Biology, Nanyang Technological University, Singapore, Singapore
- *Correspondence: K. George Chandy, ; Shashi Bhushan,
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3
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Hofschröer V, Najder K, Rugi M, Bouazzi R, Cozzolino M, Arcangeli A, Panyi G, Schwab A. Ion Channels Orchestrate Pancreatic Ductal Adenocarcinoma Progression and Therapy. Front Pharmacol 2021; 11:586599. [PMID: 33841132 PMCID: PMC8025202 DOI: 10.3389/fphar.2020.586599] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 10/30/2020] [Indexed: 02/06/2023] Open
Abstract
Pancreatic ductal adenocarcinoma is a devastating disease with a dismal prognosis. Therapeutic interventions are largely ineffective. A better understanding of the pathophysiology is required. Ion channels contribute substantially to the "hallmarks of cancer." Their expression is dysregulated in cancer, and they are "misused" to drive cancer progression, but the underlying mechanisms are unclear. Ion channels are located in the cell membrane at the interface between the intracellular and extracellular space. They sense and modify the tumor microenvironment which in itself is a driver of PDAC aggressiveness. Ion channels detect, for example, locally altered proton and electrolyte concentrations or mechanical stimuli and transduce signals triggered by these microenvironmental cues through association with intracellular signaling cascades. While these concepts have been firmly established for other cancers, evidence has emerged only recently that ion channels are drivers of PDAC aggressiveness. Particularly, they appear to contribute to two of the characteristic PDAC features: the massive fibrosis of the tumor stroma (desmoplasia) and the efficient immune evasion. Our critical review of the literature clearly shows that there is still a remarkable lack of knowledge with respect to the contribution of ion channels to these two typical PDAC properties. Yet, we can draw parallels from ion channel research in other fibrotic and inflammatory diseases. Evidence is accumulating that pancreatic stellate cells express the same "profibrotic" ion channels. Similarly, it is at least in part known which major ion channels are expressed in those innate and adaptive immune cells that populate the PDAC microenvironment. We explore potential therapeutic avenues derived thereof. Since drugs targeting PDAC-relevant ion channels are already in clinical use, we propose to repurpose those in PDAC. The quest for ion channel targets is both motivated and complicated by the fact that some of the relevant channels, for example, KCa3.1, are functionally expressed in the cancer, stroma, and immune cells. Only in vivo studies will reveal which arm of the balance we should put our weights on when developing channel-targeting PDAC therapies. The time is up to explore the efficacy of ion channel targeting in (transgenic) murine PDAC models before launching clinical trials with repurposed drugs.
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Affiliation(s)
| | - Karolina Najder
- Institute of Physiology II, University of Münster, Münster, Germany
| | - Micol Rugi
- Institute of Physiology II, University of Münster, Münster, Germany
| | - Rayhana Bouazzi
- Department of Experimental and Clinical Medicine, Section of Internal Medicine, University of Florence, Florence, Italy
| | - Marco Cozzolino
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Annarosa Arcangeli
- Department of Experimental and Clinical Medicine, Section of Internal Medicine, University of Florence, Florence, Italy
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Albrecht Schwab
- Institute of Physiology II, University of Münster, Münster, Germany
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4
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Pethő Z, Najder K, Carvalho T, McMorrow R, Todesca LM, Rugi M, Bulk E, Chan A, Löwik CWGM, Reshkin SJ, Schwab A. pH-Channeling in Cancer: How pH-Dependence of Cation Channels Shapes Cancer Pathophysiology. Cancers (Basel) 2020; 12:E2484. [PMID: 32887220 PMCID: PMC7565548 DOI: 10.3390/cancers12092484] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/25/2020] [Accepted: 08/26/2020] [Indexed: 12/20/2022] Open
Abstract
Tissue acidosis plays a pivotal role in tumor progression: in particular, interstitial acidosis promotes tumor cell invasion, and is a major contributor to the dysregulation of tumor immunity and tumor stromal cells. The cell membrane and integral membrane proteins commonly act as important sensors and transducers of altered pH. Cell adhesion molecules and cation channels are prominent membrane proteins, the majority of which is regulated by protons. The pathophysiological consequences of proton-sensitive ion channel function in cancer, however, are scarcely considered in the literature. Thus, the main focus of this review is to highlight possible events in tumor progression and tumor immunity where the pH sensitivity of cation channels could be of great importance.
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Affiliation(s)
- Zoltán Pethő
- Institute of Physiology II, University Münster, 48147 Münster, Germany; (K.N.); (L.M.T.); (M.R.); (E.B.); (A.S.)
| | - Karolina Najder
- Institute of Physiology II, University Münster, 48147 Münster, Germany; (K.N.); (L.M.T.); (M.R.); (E.B.); (A.S.)
| | - Tiago Carvalho
- Department of Biosciences, Biotechnologies, and Biopharmaceutics, University of Bari, 90126 Bari, Italy; (T.C.); (S.J.R.)
| | - Roisin McMorrow
- Department of Radiology and Nuclear Medicine, Erasmus Medical Center, 3035 GD Rotterdam, The Netherlands; (R.M.); (C.W.G.M.L.)
| | - Luca Matteo Todesca
- Institute of Physiology II, University Münster, 48147 Münster, Germany; (K.N.); (L.M.T.); (M.R.); (E.B.); (A.S.)
| | - Micol Rugi
- Institute of Physiology II, University Münster, 48147 Münster, Germany; (K.N.); (L.M.T.); (M.R.); (E.B.); (A.S.)
| | - Etmar Bulk
- Institute of Physiology II, University Münster, 48147 Münster, Germany; (K.N.); (L.M.T.); (M.R.); (E.B.); (A.S.)
| | - Alan Chan
- Percuros B.V., 2333 CL Leiden, The Netherlands;
| | - Clemens W. G. M. Löwik
- Department of Radiology and Nuclear Medicine, Erasmus Medical Center, 3035 GD Rotterdam, The Netherlands; (R.M.); (C.W.G.M.L.)
- Department of Oncology CHUV, UNIL and Ludwig Cancer Center, 1011 Lausanne, Switzerland
| | - Stephan J. Reshkin
- Department of Biosciences, Biotechnologies, and Biopharmaceutics, University of Bari, 90126 Bari, Italy; (T.C.); (S.J.R.)
| | - Albrecht Schwab
- Institute of Physiology II, University Münster, 48147 Münster, Germany; (K.N.); (L.M.T.); (M.R.); (E.B.); (A.S.)
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5
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Chimote AA, Hajdu P, Sfyris AM, Gleich BN, Wise-Draper T, Casper KA, Conforti L. Kv1.3 Channels Mark Functionally Competent CD8+ Tumor-Infiltrating Lymphocytes in Head and Neck Cancer. Cancer Res 2016; 77:53-61. [PMID: 27815390 DOI: 10.1158/0008-5472.can-16-2372] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Revised: 10/14/2016] [Accepted: 10/26/2016] [Indexed: 12/20/2022]
Abstract
Tumor-infiltrating lymphocytes (TIL) are potent mediators of an antitumor response. However, their function is attenuated in solid tumors. CD8+ T-cell effector functions, such as cytokine and granzyme production, depend on cytoplasmic Ca2+, which is controlled by ion channels. In particular, Kv1.3 channels regulate the membrane potential and Ca2+ influx in human effector memory T (TEM) cells. In this study, we assessed the contribution of reduced Kv1.3 and Ca2+ flux on TIL effector function in head and neck cancer (HNC). We obtained tumor samples and matched peripheral blood from 14 patients with HNC. CD3+ TILs were composed of 57% CD4+ (82% TEM and 20% Tregs) and 36% CD8+ cells. Electrophysiology revealed a 70% reduction in functional Kv1.3 channels in TILs as compared with peripheral blood T cells from paired patients, which was accompanied by a decrease in Ca2+ influx. Immunofluorescence analysis showed that CD8+ TILs expressing high Kv1.3 preferentially localized in the stroma. Importantly, high expression of Kv1.3 correlated with high Ki-67 and granzyme B expression. Overall, these data indicate that defective Kv1.3 channels and Ca2+ fluxes in TILs may contribute to reduced immune surveillance in HNC. Cancer Res; 77(1); 53-61. ©2016 AACR.
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Affiliation(s)
- Ameet A Chimote
- Department of Internal Medicine, Division of Nephrology, University of Cincinnati, Cincinnati, Ohio
| | - Peter Hajdu
- Department of Internal Medicine, Division of Nephrology, University of Cincinnati, Cincinnati, Ohio
| | - Alexandros M Sfyris
- Department of Internal Medicine, Division of Nephrology, University of Cincinnati, Cincinnati, Ohio
| | - Brittany N Gleich
- Department of Internal Medicine, Division of Nephrology, University of Cincinnati, Cincinnati, Ohio
| | - Trisha Wise-Draper
- Department of Internal Medicine, Division of Hematology/Oncology, University of Cincinnati, Cincinnati, Ohio
| | - Keith A Casper
- Department of Otolaryngology, University of Michigan, Ann Arbor, Michigan
| | - Laura Conforti
- Department of Internal Medicine, Division of Nephrology, University of Cincinnati, Cincinnati, Ohio.
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6
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Farag NE, Jeong D, Claydon T, Warwicker J, Boyett MR. Polyunsaturated fatty acids inhibit Kv1.4 by interacting with positively charged extracellular pore residues. Am J Physiol Cell Physiol 2016; 311:C255-68. [PMID: 27281482 DOI: 10.1152/ajpcell.00277.2015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 06/06/2016] [Indexed: 11/22/2022]
Abstract
Polyunsaturated fatty acids (PUFAs) modulate voltage-gated K(+) channel inactivation by an unknown site and mechanism. The effects of ω-6 and ω-3 PUFAs were investigated on the heterologously expressed Kv1.4 channel. PUFAs inhibited wild-type Kv1.4 during repetitive pulsing as a result of slowing of recovery from inactivation. In a mutant Kv1.4 channel lacking N-type inactivation, PUFAs reversibly enhanced C-type inactivation (Kd, 15-43 μM). C-type inactivation was affected by extracellular H(+) and K(+) as well as PUFAs and there was an interaction among the three: the effect of PUFAs was reversed during acidosis and abolished on raising K(+) Replacement of two positively charged residues in the extracellular pore (H508 and K532) abolished the effects of the PUFAs (and extracellular H(+) and K(+)) on C-type inactivation but had no effect on the lipoelectric modulation of voltage sensor activation, suggesting two separable interaction sites/mechanisms of action of PUFAs. Charge calculations suggest that the acidic head group of the PUFAs raises the pKa of H508 and this reduces the K(+) occupancy of the selectivity filter, stabilizing the C-type inactivated state.
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Affiliation(s)
- N E Farag
- Cardiovascular Medicine, School of Medicine, University of Manchester, Core Technology Facility, Manchester, United Kingdom
| | - D Jeong
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada; and
| | - T Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada; and
| | - J Warwicker
- Manchester Institute of Biotechnology, The University of Manchester, Manchester, United Kingdom
| | - M R Boyett
- Cardiovascular Medicine, School of Medicine, University of Manchester, Core Technology Facility, Manchester, United Kingdom;
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7
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ShakerIR and Kv1.5 mutant channels with enhanced slow inactivation also exhibit K⁺ o-dependent resting inactivation. Pflugers Arch 2013; 465:1545-55. [PMID: 23708835 DOI: 10.1007/s00424-013-1297-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 04/24/2013] [Accepted: 05/13/2013] [Indexed: 10/26/2022]
Abstract
Previous studies have shown that in N-type inactivation-removed Shaker (ShakerIR) channels, the T449K and T449A mutations result in enhanced slow inactivation. These mutant channels also show a loss of conductance in 0 mM K⁺ o that was attributed to an inactivation process occurring from the closed, resting state and which we refer to as resting inactivation. Similar behavior has also been observed in the Kv1.5 H463G mutant channel. To date, the time courses for the onset of and recovery from resting inactivation have been unknown, but a comparison of the kinetics for resting inactivation induced at -80 mV and slow inactivation evoked at +50 mV may provide information on whether these two processes are mechanistically related. Here, we present an analysis of the time courses for the onset of and recovery from [K⁺]o-dependent resting inactivation and depolarization-induced inactivation of these mutant channels. Despite the enhancement of slow inactivation in the ShakerIR T449K, T449A, and Kv1.5 H463G mutants, the time constant for slow inactivation at +50 mV (τ inact) was relatively insensitive to the increases or decreases of [K(+)]o, confirming that accelerated inactivation from the open state does not underlie the loss of conductance in 0 mM K⁺. For all three mutants, the time constant for resting inactivation (τ RI), induced by exposure to 0 mM K⁺ o solution at -80 mV, was at least an order of magnitude larger than τ inact. On the other hand, the time course of recovery at -80 mV of each mutant from 0 mM K(+) o-induced resting inactivation was the same as that from depolarization-induced slow inactivation. This latter result suggests that the 0 mM K⁺ o-induced resting inactivation of these mutant ShakerIR and Kv1.5 channels is mechanistically related to slow inactivation.
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8
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External Ba2+ block of human Kv1.5 at neutral and acidic pH: evidence for Ho+-induced constriction of the outer pore mouth at rest. Biophys J 2008; 95:4456-68. [PMID: 18658206 DOI: 10.1529/biophysj.108.133165] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Previous studies have shown that low pHo accelerates depolarization-induced inactivation and decreases the macroscopic conductance by reducing channel availability. To test the hypothesis that outer pore constriction underlies the decreased conductance at low pHo, external Ba2+ was used to examine the accessibility of the channel pore at rest under neutral and acidic conditions. At pHo 7.4, Ba2+ block of closed channels follows a monoexponential time course and involves a low-affinity superficial site (KD congruent with 1 mM, -80 mV, 0 mM Ko(+)) and a high-affinity site (KD congruent with 4 microM) deeper in the pore. Depolarization promotes Ba2+ dissociation and an analytical model incorporating state-dependent changes of Ba2+ affinity is presented that replicates the frequency dependence of the time course and the extent of block. Open-channel block by Ba2+ is weak. At pHo 5.5, both the access to and exit from the deep site is inhibited. These results are consistent with a low-pHo-induced conformational change in the outer pore that prevents Ba2+ binding at rest or unbinding during depolarization. If a pore constriction is involved, similar to that proposed to occur during P/C-type inactivation, this would imply that closed-state inactivation in Kv1.5 occurs under acidic conditions.
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