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Whelan SCM, Mutchler SM, Han A, Priestley C, Satlin LM, Kleyman TR, Shi S. Kcnma1 alternative splicing in mouse kidney: regulation during development and by dietary K + intake. Am J Physiol Renal Physiol 2024; 327:F49-F60. [PMID: 38779757 DOI: 10.1152/ajprenal.00100.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Revised: 04/30/2024] [Accepted: 05/08/2024] [Indexed: 05/25/2024] Open
Abstract
The pore-forming α-subunit of the large-conductance K+ (BK) channel is encoded by a single gene, KCNMA1. BK channel-mediated K+ secretion in the kidney is crucial for overall renal K+ homeostasis in both physiological and pathological conditions. BK channels achieve phenotypic diversity by various mechanisms, including substantial exon rearrangements at seven major alternative splicing sites. However, KCNMA1 alternative splicing in the kidney has not been characterized. The present study aims to identify the major splice variants of mouse Kcnma1 in whole kidney and distal nephron segments. We designed primers that specifically cross exons within each alternative splice site of mouse Kcnma1 and performed real-time quantitative RT-PCR (RT-qPCR) to quantify relative abundance of each splice variant. Our data suggest that Kcnma1 splice variants within mouse kidney are less diverse than in the brain. During postnatal kidney development, most Kcnma1 splice variants at site 5 and the COOH terminus increase in abundance over time. Within the kidney, the regulation of Kcnma1 alternative exon splicing within these two sites by dietary K+ loading is both site and sex specific. In microdissected distal tubules, the Kcnma1 alternative splicing profile, as well as its regulation by dietary K+, are distinctly different than in the whole kidney, suggesting segment and/or cell type specificity in Kcnma1 splicing events. Overall, our data provide evidence that Kcnma1 alternative splicing is regulated during postnatal development and may serve as an important adaptive mechanism to dietary K+ loading in mouse kidney.NEW & NOTEWORTHY We identified the major Kcnma1 splice variants that are specifically expressed in the whole mouse kidney or aldosterone-sensitive distal nephron segments. Our data suggest that Kcnma1 alternative splicing is developmentally regulated and subject to changes in dietary K+.
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Affiliation(s)
| | - Stephanie M Mutchler
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Agnes Han
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Catherine Priestley
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Lisa M Satlin
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, New York, United States
| | - Thomas R Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Shujie Shi
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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2
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Pang JJ. The Variety of Mechanosensitive Ion Channels in Retinal Neurons. Int J Mol Sci 2024; 25:4877. [PMID: 38732096 PMCID: PMC11084373 DOI: 10.3390/ijms25094877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 04/16/2024] [Accepted: 04/20/2024] [Indexed: 05/13/2024] Open
Abstract
Alterations in intraocular and external pressure critically involve the pathogenesis of glaucoma, traumatic retinal injury (TRI), and other retinal disorders, and retinal neurons have been reported to express multiple mechanical-sensitive channels (MSCs) in recent decades. However, the role of MSCs in visual functions and pressure-related retinal conditions has been unclear. This review will focus on the variety and functional significance of the MSCs permeable to K+, Na+, and Ca2+, primarily including the big potassium channel (BK); the two-pore domain potassium channels TRAAK and TREK; Piezo; the epithelial sodium channel (ENaC); and the transient receptor potential channels vanilloid TRPV1, TRPV2, and TRPV4 in retinal photoreceptors, bipolar cells, horizontal cells, amacrine cells, and ganglion cells. Most MSCs do not directly mediate visual signals in vertebrate retinas. On the other hand, some studies have shown that MSCs can open in physiological conditions and regulate the activities of retinal neurons. While these data reasonably predict the crossing of visual and mechanical signals, how retinal light pathways deal with endogenous and exogenous mechanical stimulation is uncertain.
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Affiliation(s)
- Ji-Jie Pang
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX 77030, USA
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3
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Modzelewska B, Drygalski K, Hady HR, Kiełczewska A, Chomentowski A, Koryciński K, Głuszyńska P, Kleszczewski T. Resveratrol Relaxes Human Gastric Smooth Muscles Through High Conductance Calcium-Activated Potassium Channel in a Nitric Oxide-independent Manner. Front Pharmacol 2022; 13:823887. [PMID: 35145416 PMCID: PMC8822120 DOI: 10.3389/fphar.2022.823887] [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: 11/28/2021] [Accepted: 01/03/2022] [Indexed: 11/25/2022] Open
Abstract
Resveratrol, as a polyphenolic compound that can be isolated from plants, and also a component of red wine has broad beneficial pharmacological properties. The aim was to investigate the role of nitric oxide and potassium channels in resveratrol-induced relaxation of human gastric smooth muscle. Gastric tissues were obtained from patients who underwent sleeve gastrectomy for severe obesity (n = 10 aged 21–48; BMI 48.21 ± 1.14). The mechanical activity from the muscle strips was detected under isometric conditions as the response to increasing concentrations of resveratrol before and after different pharmacological treatments. Resveratrol caused an observable, dose-dependent gastric muscle relaxation. The maximal response caused by the highest concentration of resveratrol was 83.49 ± 2.85% (p < 0.0001) of the control. Preincubation with L-NNA, L-NAME, or ODQ did not prevent the resveratrol-induced relaxation. Apamin, glibenclamide, 4AP or tamoxifen, did not inhibit the relaxing effect of resveratrol, as well. In turn, blocking BKCa by TEA, iberiotoxin, or charybdotoxin resulted in inhibition of resveratrol-induced relaxation (91.08 ± 2.07, p < 0.05; 95.60 ± 1.52, p < 0.01 and 89.58 ± 1.98, p < 0.05, respectively). This study provides the first observation that the relaxant effects of resveratrol in human gastric muscle strips occur directly through BKCa channels and independently of nitric oxide signaling pathways. Furthermore, there is considerable potential for further extensive clinical studies with resveratrol as an effective new drug or health supplement to treat gastrointestinal dyspepsia and other gastric hypermotility disorders.
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Affiliation(s)
- Beata Modzelewska
- Department of Biophysics, Faculty of Medicine, Medical University of Bialystok, Bialystok, Poland
- *Correspondence: Beata Modzelewska,
| | - Krzysztof Drygalski
- Department of Biophysics, Faculty of Medicine, Medical University of Bialystok, Bialystok, Poland
- Clinical Research Center, Medical University of Bialystok, Bialystok, Poland
| | - Hady Razak Hady
- Clinical Department of General and Endocrine Surgery, Medical University of Bialystok, Bialystok, Poland
| | - Aleksandra Kiełczewska
- Department of Biophysics, Faculty of Medicine, Medical University of Bialystok, Bialystok, Poland
| | - Andrzej Chomentowski
- Department of Biophysics, Faculty of Medicine, Medical University of Bialystok, Bialystok, Poland
| | - Krzysztof Koryciński
- Department of Biophysics, Faculty of Medicine, Medical University of Bialystok, Bialystok, Poland
| | - Paulina Głuszyńska
- Clinical Department of General and Endocrine Surgery, Medical University of Bialystok, Bialystok, Poland
| | - Tomasz Kleszczewski
- Department of Biophysics, Faculty of Medicine, Medical University of Bialystok, Bialystok, Poland
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Kravenska Y, Nieznanska H, Nieznanski K, Lukyanetz E, Szewczyk A, Koprowski P. The monomers, oligomers, and fibrils of amyloid-β inhibit the activity of mitoBK Ca channels by a membrane-mediated mechanism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183337. [PMID: 32380169 DOI: 10.1016/j.bbamem.2020.183337] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Revised: 04/25/2020] [Accepted: 04/28/2020] [Indexed: 02/08/2023]
Abstract
A causative agent of Alzheimer's disease (AD) is a short amphipathic peptide called amyloid beta (Aβ). Aβ monomers undergo structural changes leading to their oligomerization or fibrillization. The monomers as well as all aggregated forms of Aβ, i.e., oligomers, and fibrils, can bind to biological membranes, thereby modulating membrane mechanical properties. It is also known that some isoforms of the large-conductance calcium-activated potassium (BKCa) channel, including the mitochondrial BKCa (mitoBKCa) channel, respond to mechanical changes in the membrane. Here, using the patch-clamp technique, we investigated the impact of full-length Aβ (Aβ1-42) and its fragment, Aβ25-35, on the activity of mitoBKCa channels. We found that all forms of Aβ inhibited the activity of the mitoBKCa channel in a concentration-dependent manner. Since monomers, oligomers, and fibrils of Aβ exhibit different molecular characteristics and structures, we hypothesized that the inhibition was not due to direct peptide-protein interactions but rather to membrane-binding of the Aβ peptides. Our findings supported this hypothesis by showing that Aβ peptides block mitoBKCa channels irrespective of the side of the membrane to which they are applied. In addition, we found that the enantiomeric peptide, D-Aβ1-42, demonstrated similar inhibitory activity towards mitoBKCa channels. As a result, we proposed a general model in which all Aβ forms i.e., monomers, oligomers, and amyloid fibrils, contribute to the progression of AD by exerting a modulatory effect on mechanosensitive membrane components.
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Affiliation(s)
- Yevheniia Kravenska
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology PAS, Pasteura str. 3, Warsaw 02-093, Poland; Department of Biophysics of Ion Channels, Bogomoletz Institute of Physiology NASU, Bogomoletz str. 4, Kyiv 01-024, Ukraine.
| | - Hanna Nieznanska
- Laboratory of Electron Microscopy, Nencki Institute of Experimental Biology PAS, Pasteura str. 3, Warsaw 02-093, Poland
| | - Krzysztof Nieznanski
- Laboratory of Molecular Basis of Cell Motility, Nencki Institute of Experimental Biology PAS, Pasteura str. 3, Warsaw 02-093, Poland
| | - Elena Lukyanetz
- Department of Biophysics of Ion Channels, Bogomoletz Institute of Physiology NASU, Bogomoletz str. 4, Kyiv 01-024, Ukraine
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology PAS, Pasteura str. 3, Warsaw 02-093, Poland
| | - Piotr Koprowski
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology PAS, Pasteura str. 3, Warsaw 02-093, Poland
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Xin F, Cheng Y, Ren J, Zhang S, Liu P, Zhao H, Huang H, Wang W. The extracellular loop of the auxiliary β1-subunit is involved in the regulation of BKCa channel mechanosensitivity. Am J Physiol Cell Physiol 2018; 315:C485-C493. [DOI: 10.1152/ajpcell.00037.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The large conductance Ca2+-activated potassium (BKCa) channel is activated by stretch. The stress-regulated exon (STREX) in α-subunits is known to affect the mechanosensitivity of BKCa channels. However, in human colonic smooth muscle cells (HCoSMCs), we found that the α-subunits without STREX (ZERO-BK) and β1-subunits could be detected yet the cells were mechanosensitive. Whether the β1-subunit is involved in the regulation of BKCa mechanosensitivity is unclear. In the present study, ZERO-BK and β1-subunits were individually expressed or coexpressed in HEK293 cells and cell-attached patch-clamp techniques were used to measure BKCa currents defining mechanosensitivity. Single-channel patch-clamp recordings from HEK293 cells cotransfected with ZERO-BK and β1-subunits showed stretch sensitivity, but there was no mechanosensitivity in HEK293 cells transfected only with ZERO-BK. We also showed that expression of the β1-subunit could increase mechanosensitivity of the STREX-type α-subunits (STREX-BK). To identify the domain in β1-subunits responsible for affecting stretch sensitivity, we expressed β1- LoopDel (chimeric β1-subunits without the extracellular loop) or β1- C TermDel (chimeric β1-subunits without COOH terminus) with ZERO-BK in HEK293 cells. The data showed that deletion of the extracellular loop but not the COOH terminus of β1-subunits virtually abolished the mechanosensitivity. These results suggest that the extracellular loop of the β1-subunit is involved in the regulation of BKCa channel mechanosensitivity and that role is independent of STREX.
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Affiliation(s)
- Fang Xin
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Yuan Cheng
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Jie Ren
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
- Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Diseases, Capital Medical University, Beijing, People’s Republic of China
| | - Sitao Zhang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Ping Liu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Haiyan Zhao
- Yanjing Medical College, Capital Medical University, Beijing, People’s Republic of China
| | - Haixia Huang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
- Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Diseases, Capital Medical University, Beijing, People’s Republic of China
| | - Wei Wang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
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Xin F, Huang H, Liu P, Ren J, Zhang S, Cheng Y, Wang W. Inhibition of ZERO-BK by PKC is involved in carbachol-induced enhancement of rat colon smooth muscle motility. Neurogastroenterol Motil 2018; 30:e13312. [PMID: 29488290 DOI: 10.1111/nmo.13312] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 01/18/2018] [Indexed: 02/04/2023]
Abstract
BACKGROUND Muscarinic acetylcholine receptor (mAChR) activation is an important factor to enhance the motility of gastrointestinal (GI) smooth muscle. Large conductance Ca2+ -activated potassium (BK) channels are widely expressed in GI smooth muscle. Roles of BK in carbachol (a mAChR agonist) induced enhancement of GI motility and the molecular mechanisms remains unknown and were investigated in this study. METHODS Colonic smooth muscle (CSM) strip was perfused to record motility in vitro. The patch-clamp technique was used to record BK currents. RT-PCR was used to detect the expression of BK channels in rat CSM tissues. Two different types BK channels were constructed in HEK293 cells to investigate the regulation mechanism. Paired t tests were set with a P < .05 regarded as significant. KEY RESULTS Carbachol enhanced CSM contraction through M3 receptor (M3 R) were attenuated by IbTX, an inhibitor of BK. Carbachol inhibited BK currents in CSM cells and Go6983, an inhibitor of protein kinase C (PKC), reversed the effect. PKC activator, phorbol 12-myristate 13-acetate (PMA), inhibited BK currents. Two types of BK channels (ZERO-BK and STREX-BK) were detected in CSM. ZERO- but not STREX-BK channels expressed in HEK293 cells were inhibited by PMA. CONCLUSION Our results provide strong evidence that inhibition of ZERO-BK but not STREX-BK channels via PKC pathway is involved in the enhancement of CSM motility by mAChR activation. Besides the activation of BK by an increase in intracellular calcium, inhibition of BK played an important role in GI motility regulation during mAChR activation.
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Affiliation(s)
- F Xin
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - H Huang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - P Liu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - J Ren
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - S Zhang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - Y Cheng
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - W Wang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
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Walewska A, Kulawiak B, Szewczyk A, Koprowski P. Mechanosensitivity of mitochondrial large-conductance calcium-activated potassium channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:797-805. [PMID: 29775559 DOI: 10.1016/j.bbabio.2018.05.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 04/29/2018] [Accepted: 05/10/2018] [Indexed: 12/01/2022]
Abstract
Potassium channels have been discovered in the inner mitochondrial membrane of various cells. These channels can regulate the mitochondrial membrane potential, the matrix volume, respiration and reactive species generation. Therefore, it is believed that their activation is cytoprotective in various tissues. In our study, the single-channel activity of a large-conductance calcium-activated potassium channel (mitoBKCa) was measured by the patch-clamp technique on mitoplasts derived from mitochondria isolated from human glioma U-87 MG cells. Here, we show for the first time that mechanical stimulation of mitoBKCa channels results in an increased probability of channel opening. However, the mechanosensitivity of mitoBKCa channels was variable with some channels exhibiting no mechanosensitivity. We detected the expression of mechanosensitive BKCa-STREX exon in U-87 MG cells and hypotesize, based on previous studies demonstrating the presence of multiple BKCa splice variants that variable mechanosensitivity of mitoBKCa could be the result of the presence of diverse BKCa isoforms in mitochondria of U-87 MG cells. Our findings indicate the possible involvement of the mitoBKCa channel in mitochondria activities in which changes in membrane tension and shape play a crucial role, such as fusion/fission and cristae remodeling.
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Affiliation(s)
- Agnieszka Walewska
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Bogusz Kulawiak
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Piotr Koprowski
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland.
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Role of BK Ca in Stretch-Induced Relaxation of Colonic Smooth Muscle. BIOMED RESEARCH INTERNATIONAL 2016; 2016:9497041. [PMID: 28018918 PMCID: PMC5149602 DOI: 10.1155/2016/9497041] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 09/30/2016] [Accepted: 10/23/2016] [Indexed: 12/15/2022]
Abstract
Stretch-induced relaxation has not been clearly identified in gastrointestinal tract. The present study is to explore the role of large conductance calcium-activated potassium channels (BKCa) in stretch-induced relaxation of colon. The expression and currents of BKCa were detected and the basal muscle tone and contraction amplitude of colonic smooth muscle strips were measured. The expression of BKCa in colon is higher than other GI segments (P < 0.05). The density of BKCa currents was very high in colonic smooth muscle cells (SMCs). BKCa in rat colonic SMCs were sensitive to stretch. The relaxation response of colonic SM strips to stretch was attenuated by charybdotoxin (ChTX), a nonspecific BKCa blocker (P < 0.05). After blocking enteric nervous activities by tetrodotoxin (TTX), the stretch-induced relaxation did not change (P > 0.05). Still, ChTX and iberiotoxin (IbTX, a specific BKCa blocker) attenuated the relaxation of the colonic muscle strips enduring stretch (P < 0.05). These results suggest stretch-activation of BKCa in SMCs was involved in the stretch-induced relaxation of colon. Our study highlights the role of mechanosensitive ion channels in SMCs in colon motility regulation and their physiological and pathophysiological significance is worth further study.
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Sachs F. Mechanical transduction by ion channels: A cautionary tale. World J Neurol 2015; 5:74-87. [PMID: 28078202 PMCID: PMC5221657 DOI: 10.5316/wjn.v5.i3.74] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 08/23/2014] [Accepted: 07/17/2015] [Indexed: 02/06/2023] Open
Abstract
Mechanical transduction by ion channels occurs in all cells. The physiological functions of these channels have just begun to be elaborated, but if we focus on the upper animal kingdom, these channels serve the common sensory services such as hearing and touch, provide the central nervous system with information on the force and position of muscles and joints, and they provide the autonomic system with information about the filling of hollow organs such as blood vessels. However, all cells of the body have mechanosensitive channels (MSCs), including red cells. Most of these channels are cation selective and are activated by bilayer tension. There are also K+ selective MSCs found commonly in neurons where they may be responsible for both general anesthesia and knockout punches in the boxing ring by hyperpolarizing neurons to reduce excitability. The cationic MSCs are typically inactive under normal mechanical stress, but open under pathologic stress. The channels are normally inactive because they are shielded from stress by the cytoskeleton. The cationic MSCs are specifically blocked by the externally applied peptide GsMtx4 (aka, AT-300). This is the first drug of its class and provides a new approach to many pathologies since it is nontoxic, non-immunogenic, stable in a biological environment and has a long pharmacokinetic lifetime. Pathologies involving excessive stress are common. They produce cardiac arrhythmias, contraction in stretched dystrophic muscle, xerocytotic and sickled red cells, etc. The channels seem to function primarily as “fire alarms”, providing feedback to the cytoskeleton that a region of the bilayer is under excessive tension and needs reinforcing. The eukaryotic forms of MSCs have only been cloned in recent years and few people have experience working with them. “Newbies” need to become aware of the technology, potential artifacts, and the fundamentals of mechanics. The most difficult problem in studying MSCs is that the actual stimulus, the force applied to the channel, is not known. We don’t have direct access to the channels themselves but only to larger regions of the membrane as seen in patches. Cortical forces are shared by the bilayer, the cytoskeleton and the extracellular matrix. How much of an applied stimulus reaches the channel is unknown. Furthermore, many of these channels exist in spatial domains where the forces within a domain are different from forces outside the domain, although we often hope they are proportional. This review is intended to be a guide for new investigators who want to study mechanosensitive ion channels.
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Wan XJ, Zhao HC, Zhang P, Huo B, Shen BR, Yan ZQ, Qi YX, Jiang ZL. Involvement of BK channel in differentiation of vascular smooth muscle cells induced by mechanical stretch. Int J Biochem Cell Biol 2015; 59:21-9. [DOI: 10.1016/j.biocel.2014.11.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 11/13/2014] [Accepted: 11/25/2014] [Indexed: 12/26/2022]
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Palmitoylation of STREX domain confers cerebroside sensitivity to the BKCa channel. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2451-9. [DOI: 10.1016/j.bbamem.2014.06.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Revised: 05/15/2014] [Accepted: 06/09/2014] [Indexed: 11/19/2022]
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Li HJ, Zhang YJ, Zhou L, Han F, Wang MY, Xue MQ, Qi Z. Chlorpromazine confers neuroprotection against brain ischemia by activating BKCa channel. Eur J Pharmacol 2014; 735:38-43. [PMID: 24755143 DOI: 10.1016/j.ejphar.2014.04.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 04/09/2014] [Accepted: 04/10/2014] [Indexed: 01/13/2023]
Abstract
Chlorpromazine (CPZ) is a well-known antipsychotic drug, still widely being used to treat symptoms of schizophrenia, psychotic depression and organic psychoses. We have previously reported that CPZ activates the BKCa (KCa1.1) channel at whole cell level. In the present study, we demonstrated that CPZ increased the single channel open probability of the BKCa channels without changing its single channel amplitude. As BKCa channel is one of the molecular targets of brain ischemia, we explored a possible new use of this old drug on ischemic brain injury. In middle cerebral artery occlusion (MCAO) focal cerebral ischemia, a single intraperitoneal injection of CPZ at several dosages (5mg/kg, 10mg/kg and 20mg/kg) could exert a significant neuroprotective effect on the brain damage in a dose- and time-dependent manner. Furthermore, blockade of BKCa channels abolished the neuroprotective effect of CPZ on MCAO, suggesting that the effect of CPZ is mediated by activation of the BKCa channel. These results demonstrate that CPZ could reduce focal cerebral ischemic damage through activating BKCa channels and merits exploration as a potential therapeutic agent for treating ischemic stroke.
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Affiliation(s)
- Hua-Juan Li
- Department of Basic Medical Sciences, Medical College of Xiamen University, Xiang'an Nan Lu, Xiamen 361102, China
| | - Yu-Jiao Zhang
- Department of Basic Medical Sciences, Medical College of Xiamen University, Xiang'an Nan Lu, Xiamen 361102, China
| | - Li Zhou
- Department of Basic Medical Sciences, Medical College of Xiamen University, Xiang'an Nan Lu, Xiamen 361102, China
| | - Feng Han
- College of Pharmaceutical Sciences, Zhejiang University, 388 Yuhangtang Road, Hangzhou 310058, China
| | - Ming-Yan Wang
- Department of Basic Medical Sciences, Medical College of Xiamen University, Xiang'an Nan Lu, Xiamen 361102, China
| | - Mao-Qiang Xue
- Department of Basic Medical Sciences, Medical College of Xiamen University, Xiang'an Nan Lu, Xiamen 361102, China.
| | - Zhi Qi
- Department of Basic Medical Sciences, Medical College of Xiamen University, Xiang'an Nan Lu, Xiamen 361102, China.
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Hristov KL, Smith AC, Parajuli SP, Malysz J, Petkov GV. Large-conductance voltage- and Ca2+-activated K+ channel regulation by protein kinase C in guinea pig urinary bladder smooth muscle. Am J Physiol Cell Physiol 2013; 306:C460-70. [PMID: 24352333 DOI: 10.1152/ajpcell.00325.2013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Large-conductance voltage- and Ca(2+)-activated K(+) (BK) channels are critical regulators of detrusor smooth muscle (DSM) excitability and contractility. PKC modulates the contraction of DSM and BK channel activity in non-DSM cells; however, the cellular mechanism regulating the PKC-BK channel interaction in DSM remains unknown. We provide a novel mechanistic insight into BK channel regulation by PKC in DSM. We used patch-clamp electrophysiology, live-cell Ca(2+) imaging, and functional studies of DSM contractility to elucidate BK channel regulation by PKC at cellular and tissue levels. Voltage-clamp experiments showed that pharmacological activation of PKC with PMA inhibited the spontaneous transient BK currents in native freshly isolated guinea pig DSM cells. Current-clamp recordings revealed that PMA significantly depolarized DSM membrane potential and inhibited the spontaneous transient hyperpolarizations in DSM cells. The PMA inhibitory effects on DSM membrane potential were completely abolished by the selective BK channel inhibitor paxilline. Activation of PKC with PMA did not affect the amplitude of the voltage-step-induced whole cell steady-state BK current or the single BK channel open probability (recorded in cell-attached mode) upon inhibition of all major Ca(2+) sources for BK channel activation with thapsigargin, ryanodine, and nifedipine. PKC activation with PMA elevated intracellular Ca(2+) levels in DSM cells and increased spontaneous phasic and nerve-evoked contractions of DSM isolated strips. Our results support the concept that PKC activation leads to a reduction of BK channel activity in DSM via a Ca(2+)-dependent mechanism, thus increasing DSM contractility.
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Affiliation(s)
- Kiril L Hristov
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina
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Takahashi K, Naruse K. Stretch-activated BK channel and heart function. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2013; 110:239-44. [PMID: 23281538 DOI: 10.1016/j.pbiomolbio.2012.08.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The heart is an organ that is exposed to extreme dynamic mechanical stimuli. From birth till death, the heart indefinitely repeats periodic contraction and dilation, i.e., shortening and elongation of cardiomyocytes. Mechanical stretch elicits a change in heart rate and may cause arrhythmia if it is excessive. Thus, mechanosensitivity is crucial to heart function. The molecule that is substantially involved in mechanosensitivity is a stretch-activated ion channel. Among several ion channels believed to be activated by stretch in the heart, the stretch-activated KCa (SAKCA) channel, a member of the group of large conductance (Big Potassium, BK) channels, shows a mechanosensitive (MS) response to membrane stretch. As BK channels respond to voltage and intracellular calcium concentration with large conductance, they are considered to be involved in repolarization after depolarization. Some BK channels are known to be activated by stretch and are expressed in a number of cells, including human osteoblasts and guinea pig intestinal neurons. The SAKCA channel was found to be sensitive to stretch in the chick heart. Given that the cardiomyocyte is unremittingly exposed to contraction and dilation and that it generates action potential and its contractility is modulated by intracellular calcium concentration, the SAKCA channel, which is dependent voltage and calcium, may be involved in action potential generation. It was recently reported that a BK channel is involved in the modulation of heart rate in the mouse. Further studies regarding the role of MS BK channels, including SAKCA, in the modulation of heart rate and contractility are expected.
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Affiliation(s)
- Ken Takahashi
- Department of Cardiovascular Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
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15
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Takahashi K, Kakimoto Y, Toda K, Naruse K. Mechanobiology in cardiac physiology and diseases. J Cell Mol Med 2013; 17:225-32. [PMID: 23441631 PMCID: PMC3822585 DOI: 10.1111/jcmm.12027] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2012] [Accepted: 01/11/2013] [Indexed: 11/28/2022] Open
Abstract
Mechanosensitivity is essential for heart function just as for all other cells and organs in the body, and it is involved in both normal physiology and diseases processes of the cardiovascular system. In this review, we have outlined the relationship between mechanosensitivity and heart physiology, including the Frank-Starling law of the heart and mechanoelectric feedback. We then focused on molecules involved in mechanotransduction, particularly mechanosensitive ion channels. We have also discussed the involvement of mechanosensitivity in heart diseases, such as arrhythmias, hypertrophy and ischaemic heart disease. Finally, mechanobiology in cardiogenesis is described with regard to regenerative medicine.
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Affiliation(s)
- Ken Takahashi
- Department of Cardiovascular Physiology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
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16
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Beyder A, Farrugia G. Targeting ion channels for the treatment of gastrointestinal motility disorders. Therap Adv Gastroenterol 2012; 5:5-21. [PMID: 22282704 PMCID: PMC3263980 DOI: 10.1177/1756283x11415892] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Gastrointestinal (GI) functional and motility disorders are highly prevalent and responsible for long-term morbidity and sometimes mortality in the affected patients. It is estimated that one in three persons has a GI functional or motility disorder. However, diagnosis and treatment of these widespread conditions remains challenging. This partly stems from the multisystem pathophysiology, including processing abnormalities in the central and peripheral (enteric) nervous systems and motor dysfunction in the GI wall. Interstitial cells of Cajal (ICCs) are central to the generation and propagation of the cyclical electrical activity and smooth muscle cells (SMCs) are responsible for electromechanical coupling. In these and other excitable cells voltage-sensitive ion channels (VSICs) are the main molecular units that generate and regulate electrical activity. Thus, VSICs are potential targets for intervention in GI motility disorders. Research in this area has flourished with advances in the experimental methods in molecular and structural biology and electrophysiology. However, our understanding of the molecular mechanisms responsible for the complex and variable electrical behavior of ICCs and SMCs remains incomplete. In this review, we focus on the slow waves and action potentials in ICCs and SMCs. We describe the constituent VSICs, which include voltage-gated sodium (Na(V)), calcium (Ca(V)), potassium (K(V), K(Ca)), chloride (Cl(-)) and nonselective ion channels (transient receptor potentials [TRPs]). VSICs have significant structural homology and common functional mechanisms. We outline the approaches and limitations and provide examples of targeting VSICs at the pores, voltage sensors and alternatively spliced sites. Rational drug design can come from an integrated view of the structure and mechanisms of gating and activation by voltage or mechanical stress.
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Affiliation(s)
- Arthur Beyder
- Enteric Neuroscience Program, Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN, USA
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17
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Chi S, Cai W, Liu P, Zhang Z, Chen X, Gao L, Qi J, Bi L, Chen L, Qi Z. Baifuzi reduces transient ischemic brain damage through an interaction with the STREX domain of BKCa channels. Cell Death Dis 2011; 1:e13. [PMID: 21364615 PMCID: PMC3039290 DOI: 10.1038/cddis.2009.10] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Stroke is a long-term disability and one of the leading causes of death. However, no successful therapeutic intervention is available for the majority of stroke patients. In this study, we explored a traditional Chinese medicine Baifuzi (Typhonium giganteum Engl.). We show, at first, that the ethanol extract of Baifuzi exerts neuroprotective effects against brain damage induced by transient global or focal cerebral ischemia in rats and mice. Second, the extract activated large-conductance Ca(2+)-activated K(+) channel (BK(Ca)) channels, and BK(Ca) channel blockade suppressed the neuroprotection of the extract, suggesting that the BK(Ca) is the molecular target of Baifuzi. Third, Baifuzi cerebroside (Baifuzi-CB), purified from its ethanol extract, activated BK(Ca) channels in a manner similar to that of the extract. Fourth, the stress axis hormone-regulated exon (STREX) domain of the BK(Ca) channel directly interacted with Baifuzi-CB, and its deletion suppressed channel activation by Baifuzi-CB. These results indicate that Baifuzi-CB activated the BK(Ca) channel through its direct interaction with the STREX domain of the channel and suggests that Baifuzi-CB merits exploration as a potential therapeutic agent for treating brain ischemia.
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Affiliation(s)
- S Chi
- Department of Physiology, Medical College of Xiamen University, Xiamen, China
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18
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Wang W, Huang H, Hou D, Liu P, Wei H, Fu X, Niu W. Mechanosensitivity of STREX-lacking BKCa channels in the colonic smooth muscle of the mouse. Am J Physiol Gastrointest Liver Physiol 2010; 299:G1231-40. [PMID: 20864656 DOI: 10.1152/ajpgi.00268.2010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Stretch sensitivity of Ca²(+)-activated large-conductance K(+) channels (BK(Ca)) has been observed in a variety of cell types and considered to be a potential mechanism in mechanoelectric transduction (MET). Mechanical stress is a major stimulator for the smooth muscle in the gastrointestinal (GI) tract. However, much about the role and mechanism of MET in GI smooth muscles remains unknown. The BK(Ca) shows a functional diversity due to intensive Slo I alternative splicing and different α/β-subunit assembly in various cells. The stress-regulated exon (STREX) insert is suggested to be an indispensable domain for the mechanosensitivity of BK(Ca). The purpose of this study was to determine whether the BK(Ca) in colonic myocytes of the adult mouse is sensitive to mechanical stimulation and whether the STREX insert is a crucial segment for the BK(Ca) mechanosensitivity. The α- and β1-subunit mRNAs and the α-subunit protein of the BK(Ca) channels were detected in the colonic muscularis. We found that the BK(Ca) STREX-lacking variant was abundantly expressed in the smooth muscle, whereas the STREX variant was not detectable. We demonstrated that the STREX-lacking BK(Ca) channels were also sensitive to membrane stretch. We suggest that in addition to the STREX domain, there are other additional structures in the channel responsible for mechanically coupling with the cell membrane.
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Affiliation(s)
- Wei Wang
- Dept. of Physiology, Capital Medical Univ., Beijing, PR China
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19
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Zhao HC, Agula H, Zhang W, Wang F, Sokabe M, Li LM. Membrane stretch and cytoplasmic Ca2+ independently modulate stretch-activated BK channel activity. J Biomech 2010; 43:3015-9. [DOI: 10.1016/j.jbiomech.2010.06.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 06/28/2010] [Accepted: 06/30/2010] [Indexed: 12/23/2022]
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20
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Ide T, Takeuchi Y, Noji H, Tabata KV. Simultaneous optical and electrical single channel recordings on a PEG glass. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:8540-8543. [PMID: 20030321 DOI: 10.1021/la9045594] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Single molecule imaging of working ion-channels is much more difficult than that of water-soluble proteins because of the fragile nature of membranes and lateral diffusion of particles in the membranes, which does not allow fluorescent contamination for optical single channel recording. In this report, we reconstituted maxi-potassium channels from porcine uterine smooth muscle into artificial planar bilayers formed on poly(ethylene glycol) (PEG) modified glass and performed simultaneous optical and electrical recording of the single channels. The channels were immobilized in the membranes by anchoring to PEG molecules on the glass. The technique developed in this study should pave the way for single molecule pharmacology of ion-channels.
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Affiliation(s)
- Toru Ide
- Soft Biosystem Group, Laboratories for Nanobiology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.
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21
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Iribe G, Jin H, Kaihara K, Naruse K. Effects of axial stretch on sarcolemmal BKCachannels in post-hatch chick ventricular myocytes. Exp Physiol 2010; 95:699-711. [DOI: 10.1113/expphysiol.2009.051896] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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22
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Aydar E, Palmer CP. Polycystic kidney disease channel and synaptotagmin homologues play roles in schizosaccharomyces pombe cell wall synthesis/repair and membrane protein trafficking. J Membr Biol 2009; 229:141-52. [PMID: 19543678 DOI: 10.1007/s00232-009-9180-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Accepted: 06/02/2009] [Indexed: 11/24/2022]
Abstract
Eukaryotic cells can sense a wide variety of environmental stresses, including changes in temperature, pH, osmolarity and nutrient availability. They respond to these changes through a variety of signal-transduction mechanisms, including activation of Ca(2+)-dependent signaling pathways. This research has discovered important implications in the function(s) of polycystic kidney disease (PKD) channels and the mechanisms through which they act in the control of cell growth and cell polarity in Schizosaccharomyces pombe by ion channel-mediated Ca(2+) signaling. Pkd2 was expressed maximally during the exponential growth phase. At the cell surface pkd2 was localized at the cell tip during the G(2) phase of the cell cycle, although following cell wall damage, the cell surface-expressed protein relocalized to the whole plasma membrane. Pkd2 depletion affected Golgi trafficking, resulting in a buildup of vesicles at the cell poles, and strongly affected plasma membrane protein delivery. Surface-localized pkd2 was present in the plasma membrane for a very short time and was rapidly internalized. Internalization was dependent on Ca(2+), enhanced by amphipaths and inhibited by gadolinium. The pkd2 protein was in a complex with a yeast synaptotagmin homologue and myosin V. Depletion of pkd2 severely affected the localization of glucan synthase. A role for pkd2 in a cell polarity and cell wall synthesis signaling complex with a synaptotagmin homologue, myosin V and glucan synthase is proposed.
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Affiliation(s)
- Ebru Aydar
- Institute for Health Research and Policy, London Metropolitan University, 166-220 Holloway Road, London, N7 8DB, UK
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23
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Hammami S, Willumsen NJ, Olsen HL, Morera FJ, Latorre R, Klaerke DA. Cell volume and membrane stretch independently control K+ channel activity. J Physiol 2009; 587:2225-31. [PMID: 19289549 DOI: 10.1113/jphysiol.2008.163550] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
A number of potassium channels including members of the KCNQ family and the Ca(2+) activated IK and SK, but not BK, are strongly and reversibly regulated by small changes in cell volume. It has been argued that this general regulation is mediated through sensitivity to changes in membrane stretch. To test this hypothesis we have studied the regulation of KCNQ1 and BK channels after expression in Xenopus oocytes. Results from cell-attached patch clamp studies (approximately 50 microm(2) macropatches) in oocytes expressing BK channels demonstrate that the macroscopic volume-insensitive BK current increases with increasing negative hydrostatic pressure (suction) applied to the pipette. Thus, at a pipette pressure of -5.0 +/- 0.1 mmHg the increase amounted to 381 +/- 146% (mean +/- S.E.M., n = 6, P < 0.025). In contrast, in oocytes expressing the strongly volume-sensitive KCNQ1 channel, the current was not affected by membrane stretch. The results indicate that (1) activation of BK channels by local membrane stretch is not mimicked by membrane stress induced by cell swelling, and (2) activation of KCNQ1 channels by cell volume increase is not mediated by local tension in the cell membrane. We conclude that stretch and volume sensitivity can be considered two independent regulatory mechanisms.
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Affiliation(s)
- Sofia Hammami
- Department of Biology, University of Copenhagen, Denmark
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24
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Differential expression of BK channel isoforms and β-subunits in rat neuro-vascular tissues. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:380-9. [DOI: 10.1016/j.bbamem.2008.10.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Revised: 09/18/2008] [Accepted: 10/06/2008] [Indexed: 12/30/2022]
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25
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Hurst AC, Gottlieb PA, Martinac B. Concentration dependent effect of GsMTx4 on mechanosensitive channels of small conductance in E. coli spheroplasts. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 38:415-25. [PMID: 19132368 DOI: 10.1007/s00249-008-0386-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2008] [Revised: 11/19/2008] [Accepted: 11/25/2008] [Indexed: 10/21/2022]
Abstract
The spider peptide GsMTx4, at saturating concentration of 5 muM, is an effective and specific inhibitor for stretch-activated mechanosensitive (MS) channels found in a variety of eukaryotic cells. Although the structure of the peptide has been solved, the mode of action remains to be determined. Because of its amphipathic structure, the peptide is proposed to interact with lipids at the boundaries of the MS channel proteins. In addition, GsMTx4 has antimicrobial effects, inhibiting growth of several species of bacteria in the range of 5-64 microM. Previous studies on prokaryotic MS channels, which serve as model systems to explore the principle of MS channel gating, have shown that various amphipathic compounds acting at the protein-lipid interface affect MS channel gating. We have therefore analyzed the effect of different concentrations of extracellular GsMTx4 on MS channels of small conductance, MscS and MscK, in the cytoplasmic membrane of wild-type E. coli spheroplasts using the patch-clamp technique. Our study shows that the peptide GsMTx4 exhibits a biphasic response in which peptide concentration determines inhibition or potentiation of activity in prokaryotic MS channels. At low peptide concentrations of 2 and 4 microM the gating of the prokaryotic MS channels was hampered, manifested by a decrease in pressure sensitivity. In contrast, application of peptide at concentrations of 12 and 20 microM facilitated prokaryotic MS channel opening by increasing the pressure sensitivity.
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Affiliation(s)
- Annette C Hurst
- Molecular Biophysics Laboratory, School of Biomedical Sciences, University of Queensland, St Lucia, QLD, 4072, Australia
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26
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Markin VS, Volkov AG, Jovanov E. Active movements in plants: Mechanism of trap closure by Dionaea muscipula Ellis. PLANT SIGNALING & BEHAVIOR 2008; 3:778-83. [PMID: 19513230 PMCID: PMC2637513 DOI: 10.4161/psb.3.10.6041] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Accepted: 04/04/2008] [Indexed: 05/08/2023]
Abstract
The Venus flytrap (Dionaea muscipula Ellis) captures insects with one of the most rapid movements in the plant kingdom. We investigated trap closure by mechanical and electrical stimuli using the novel charge-injection method and high-speed recording. We proposed a new hydroelastic curvature mechanism, which is based on the assumption that the lobes possess curvature elasticity and are composed of outer and inner hydraulic layers with different hydrostatic pressure. The open state of the trap contains high elastic energy accumulated due to the hydrostatic pressure difference between the hydraulic layers of the lobe. Stimuli open pores connecting the two layers, water rushes from one hydraulic layer to another, and the trap relaxes to the equilibrium configuration corresponding to the closed state. In this paper we derived equations describing this system based on elasticity Hamiltonian and found closing kinetics. The novel charge-injection stimulation method gives insight into mechanisms of the different steps of signal transduction and response in the plant kingdom.
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Affiliation(s)
- Vladislav S Markin
- Department of Neurology; University of Texas; Southwestern Medical Center; Dallas, Texas USA
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27
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Zhao H, Sokabe M. Tuning the mechanosensitivity of a BK channel by changing the linker length. Cell Res 2008; 18:871-8. [DOI: 10.1038/cr.2008.88] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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Abstract
PURPOSE OF REVIEW Large, BK (calcium-activated potassium) channels are now regarded as relevant players in many aspects of renal physiology, including potassium secretion. This review will highlight recent discoveries regarding the function and localization of BK in the kidney. RECENT FINDINGS Patch clamp electrophysiology has revealed BK in cultured podocytes, glomerular mesangial cells, and in several tubule segments including principal cells (connecting tubules/principal cells), and intercalated cells of connecting tubules and cortical collecting ducts. Flow-induced potassium secretion is mediated by BK in the distal nephron and may be partly the result of shear stress-induced increases in cell calcium concentrations. ROMK-/- and wild-type mice on a high potassium diet exhibit BK-mediated potassium secretion, and studies of BK-alpha-/- and BK-beta1-/- mice suggest that flow-induced potassium secretion is mediated by BK-alpha/beta1, which is specifically localized in the apical membrane of the connecting tubule of the mouse and connecting tubule plus initial cortical collecting duct of the rabbit. SUMMARY BK channels, located in glomerular cells and in many nephron segments, especially mediate potassium secretion in the combined condition of potassium adaptation and high flow. Understanding the molecular makeup of BK in specific renal cells and the dietary and physiological conditions for their expression can yield improved potassium-sparing compounds.
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Affiliation(s)
- P Richard Grimm
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, 985850 Nebraska Medical Center, Omaha, Nebraska 68198-5850, USA
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29
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Kloda A, Lua L, Hall R, Adams DJ, Martinac B. Liposome reconstitution and modulation of recombinant N-methyl-D-aspartate receptor channels by membrane stretch. Proc Natl Acad Sci U S A 2007; 104:1540-5. [PMID: 17242368 PMCID: PMC1780071 DOI: 10.1073/pnas.0609649104] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2006] [Indexed: 11/18/2022] Open
Abstract
In this study, the heteromeric N-methyl-D-aspartate (NMDA) receptor channels composed of NR1a and NR2A subunits were expressed, purified, reconstituted into liposomes, and characterized by using the patch clamp technique. The protein exhibited the expected electrophysiological profile of activation by glutamate and glycine and internal Mg2+ blockade. We demonstrated that the mechanical energy transmitted to membrane-bound NMDA receptor channels can be exerted directly by tension developed in the lipid bilayer. Membrane stretch and application of arachidonic acid potentiated currents through NMDA receptor channels in the presence of intracellular Mg2+. The correlation of membrane tension induced by either mechanical or chemical stimuli with the physiological Mg2+ block of the channel suggests that the synaptic transmission can be altered if NMDA receptor complexes experience local changes in bilayer thickness caused by dynamic targeting to lipid microdomains, electrocompression, or chemical modification of the cell membranes. The ability to study gating properties of NMDA receptor channels in artificial bilayers should prove useful in further study of structure-function relationships and facilitate discoveries of new therapeutic agents for treatment of glutamate-mediated excitotoxicity or analgesic therapies.
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Affiliation(s)
| | - Linda Lua
- SRC Protein Expression Facility, Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Rhonda Hall
- SRC Protein Expression Facility, Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
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30
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Hill K, Schaefer M. TRPA1 is differentially modulated by the amphipathic molecules trinitrophenol and chlorpromazine. J Biol Chem 2007; 282:7145-53. [PMID: 17218316 DOI: 10.1074/jbc.m609600200] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPA1, a poorly selective Ca(2+)-permeable cation channel, is expressed in peripheral sensory neurons, where it is considered to contribute to a variety of sensory processes such as the detection of painful stimuli. Furthermore, TRPA1 was also identified in hair cells of the inner ear, but its involvement in sensing mechanical forces is still being controversially discussed. Amphipathic molecules such as trinitrophenol and chlorpromazine have been shown to provide useful tools to study mechanosensitive channels. Depending on their charge, they partition in the inner or outer sheets of the lipid bilayer, causing a curvature of the membrane, which has been demonstrated to activate or inhibit mechanosensitive ion channels. In the present study, we investigated the effect of these molecules on TRPA1 gating. TRPA1 was robustly activated by the anionic amphipathic molecule trinitrophenol. The whole-cell and single channel properties resemble those previously described for TRPA1. Moreover, we could show that the toxin GsMTx-4 acts on TRPA1. In addition to its recently described role as an inhibitor of stretch-activated ion channels, it serves as a potent activator of TRPA1 channels. On the other hand, the positively charged drug chlorpromazine modulates activated TRPA1 currents in a voltage-dependent way. The exposure of activated TRPA1 channels to chlorpromazine led to a block at positive potentials and an increased open probability at negative potentials. The variability in the shape of the I-V curve gives a first indication that native mechanically activated TRPA1 currents must not necessarily exhibit the same biophysical properties as ligand-activated TRPA1 currents.
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Affiliation(s)
- Kerstin Hill
- Institut für Pharmakologie, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Thielallee 67-73, 14195 Berlin, Germany
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31
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Yuan C, O'Connell RJ, Jacob RF, Mason RP, Treistman SN. Regulation of the gating of BKCa channel by lipid bilayer thickness. J Biol Chem 2007; 282:7276-86. [PMID: 17209047 DOI: 10.1074/jbc.m607593200] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transmembrane segments of ion channels tend to match the hydrophobic thickness of lipid bilayers to minimize mismatch energy and to maintain their proper organization and function. To probe how ion channels respond to mismatch with lipid bilayers of different thicknesses, we examined the single channel activities of BK(Ca) (hSlo alpha-subunit) channels in planar bilayers of binary mixtures of DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) with phosphatidylcholines (PCs) of varying chain lengths, including PC 14:1, PC 18:1, PC 22:1, PC 24:1, and with porcine brain sphingomyelin. Bilayer thickness and structure was measured with small angle x-ray diffraction and atomic force microscopy. The open probability (P(o)) of the BK(Ca) channel was finely tuned by bilayer thickness, first decreasing with increases in bilayer thickness from PC 14:1 to PC 22:1 and then increasing from PC 22:1 to PC 24:1 and to porcine brain sphingomyelin. Single channel kinetic analyses revealed that the mean open time of the channel increased monotonically with bilayer thickness and, therefore, could not account for the biphasic changes in P(o). The mean closed time increased with bilayer thickness from PC 14:1 up to PC 22:1 and then decreased with further increases in bilayer thickness to PC 24:1 and sphingomyelin, correlating with changes in P(o). This is consistent with the proposition that bilayer thickness affects channel activity mainly through altering the stability of the closed state. We suggest a simple mechanical model that combines forces of lateral stress within the lipid bilayer with local hydrophobic mismatch between lipids and the protein to account for the biphasic modulation of BK(Ca) gating.
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Affiliation(s)
- Chunbo Yuan
- Brudnick Neuropsychiatric Research Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01604, USA
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Matthews BD, Thodeti CK, Ingber DE. Activation of Mechanosensitive Ion Channels by Forces Transmitted Through Integrins and the Cytoskeleton. MECHANOSENSITIVE ION CHANNELS, PART A 2007. [DOI: 10.1016/s1063-5823(06)58003-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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3.5 Billion Years of Mechanosensory Transduction: Structure and Function of Mechanosensitive Channels in Prokaryotes. CURRENT TOPICS IN MEMBRANES 2007. [DOI: 10.1016/s1063-5823(06)58002-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Shlyonsky VG, Markin VS, Andreeva I, Pedersen SE, Simon SA, Benos DJ, Ismailov II. Role of membrane curvature in mechanoelectrical transduction: Ion carriers nonactin and valinomycin sense changes in integral bending energy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1723-31. [PMID: 17069752 DOI: 10.1016/j.bbamem.2006.09.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2006] [Revised: 09/13/2006] [Accepted: 09/15/2006] [Indexed: 10/24/2022]
Abstract
We describe the phenomenon of mechanoelectrical transduction in macroscopic lipid bilayer membranes modified by two cation-selective ionophores, valinomycin and nonactin. We found that bulging these membranes, while maintaining the membrane tension constant, produced a marked supralinear increase in specific carrier-mediated conductance. Analyses of the mechanisms involved in mechanoelectrical transduction induced by the imposition of a hydrostatic pressure gradient or by an amphipathic compound chlorpromazine reveal similar changes in the charge carrier motility and carrier reaction rates at the interface(s). Furthermore, the relative change in membrane conductance was independent of membrane diameter, but was directly proportional to the square of membrane curvature, thus relating the observed phenomena to the bilayer bending energy. Extrapolated to biological membranes, these findings indicate that ion transport in cells can be influenced simply by changing shape of the membrane, without a change in membrane tension.
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Affiliation(s)
- V Gh Shlyonsky
- Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Abstract
BACKGROUND AND PURPOSE Sulphatides are sulphated glycosphingolipids expressed on the surface of many cell types, particularly neurones. Changes in sulphatide species or content have been associated with epilepsy and Alzheimer's disease. As the large conductance, calcium sensitive K(+) channel (BK(Ca)) are modulated by membrane lipids, the aim of the study was to explore possible effects of sulphatides on BK(Ca) channels. EXPERIMENTAL APPROACH Using patch-clamp techniques, we studied effects of exogenous sulphatides on BK(Ca) channels expressed in Chinese hamster ovary cells. KEY RESULTS Sulphatides reversibly increased the whole-cell current and the single channel open probability of BK(Ca) channels dose-dependently. The EC(50) value on the channel at +10 mV was 1.6 microM and the Hill coefficient was 2.5. In inside-out patches, sulphatides increased the single channel open probability from both intra- and extra-cellular faces of the membrane, but more effectively with external application. Furthermore, activation of the channels by sulphatides was independent of intracellular Ca(2+) concentration. Sulphatides also shifted the activation curve of the channels to less positive membrane potentials. Mutant BK(Ca) channels lacking a 59 aminoacid region important for amphipath activation (STREX) were less activated by the sulphatides. CONCLUSIONS AND IMPLICATIONS Sulphatides are novel activators of BK(Ca) channels, independent of intracellular Ca(2+) or other signalling molecules but partly dependent on the STREX sequence of the channel protein. As changes of sulphatide content are associated with neuronal dysfunction, as in epilepsy and Alzheimer's disease, our results imply that these effects of sulphatides may play important pathophysiological roles in regulation of BK(Ca) channels.
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Affiliation(s)
- S Chi
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics Beijing, PR China
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- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics Beijing, PR China
- Author for correspondence:
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Hamill OP. Twenty odd years of stretch-sensitive channels. Pflugers Arch 2006; 453:333-51. [PMID: 17021800 DOI: 10.1007/s00424-006-0131-0] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Accepted: 06/27/2006] [Indexed: 01/15/2023]
Abstract
After formation of the giga-seal, the membrane patch can be stimulated by hydrostatic or osmotic pressure gradients applied across the patch. This feature led to the discovery of stretch-sensitive or mechanosensitive (MS) channels, which are now known to be ubiquitously expressed in cells representative of all the living kingdoms. In addition to mechanosensation, MS channels have been implicated in many basic cell functions, including regulation of cell volume, shape, and motility. The successful cloning, overexpression, and crystallization of bacterial MS channel proteins combined with patch clamp and modeling studies have provided atomic insight into the working of these nanomachines. In particular, studies of MS channels have revealed new understanding of how the lipid bilayer modulates membrane protein function. Three major membrane protein families, transient receptor potential, 2 pore domain K(+), and the epithelial Na(+) channels, have been shown to form MS channels in animal cells, and their polymodal activation embrace fields far beyond mechanosensitivity. The discovery of new drugs highly selective for MS channels ("mechanopharmaceutics") and the demonstration of MS channel involvement in several major human diseases ("mechanochannelopathies") provide added motivation for devising new techniques and approaches for studying MS channels.
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Affiliation(s)
- O P Hamill
- Neurosciences and Cell Biology, UTMB, Galveston, TX, 77555, USA.
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