1
|
Li J, Gao W, Zhang Y, Cheng F, Eriksson JE, Etienne-Manneville S, Jiu Y. Engagement of vimentin intermediate filaments in hypotonic stress. J Cell Biochem 2019; 120:13168-13176. [PMID: 30887571 DOI: 10.1002/jcb.28591] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 02/01/2019] [Accepted: 02/14/2019] [Indexed: 11/08/2022]
Abstract
Intermediate filaments (IFs) play a key role in the control of cell structure and morphology, cell mechano-responses, migration, proliferation, and apoptosis. However, the mechanisms regulating IFs organization in motile adhesive cells under certain physical/pathological conditions remain to be fully understood. In this study, we found hypo-osmotic-induced stress results in a dramatic but reversible rearrangement of the IF network. Vimentin and nestin IFs are partially depolymerized as they are redistributed throughout the cell cytoplasm after hypo-osmotic shock. This spreading of the IFs requires an intact microtubule network and the motor protein associated transportation. Both nocodazole treatment and depletion of kinesin-1 (KIF5B) block the hypo-osmotic shock-induced rearrangement of IFs showing that the dynamic behavior of IFs largely depends on microtubules and kinesin-dependent transport. Moreover, we show that cell survival rates are dramatically decreased in response to hypo-osmotic shock, which was more severe by vimentin IFs depletion, indicating its contribution to osmotic endurance. Collectively, these results reveal a critical role of vimentin IFs under hypotonic stress and provide evidence that IFs are important for the defense mechanisms during the osmotic challenge.
Collapse
Affiliation(s)
- Jian Li
- CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China
| | - Wei Gao
- CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yue Zhang
- CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Fang Cheng
- School of Pharmaceutical Sciences (Shenzhen), SYSU, China
| | - John E Eriksson
- Cell Biology, Biosciences, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.,Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Turku, Finland
| | - Sandrine Etienne-Manneville
- Institut Pasteur Paris CNRS UMR3691, Cell Polarity, Migration and Cancer Unit, Equipe Labellisée Ligue Contre le Cancer, Paris, France
| | - Yaming Jiu
- CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| |
Collapse
|
2
|
Mitsuyama H, Yokoshiki H, Irie Y, Watanabe M, Mizukami K, Tsutsui H. Involvement of the phosphatidylinositol kinase pathway in augmentation of ATP-sensitive K+ channel currents by hypo-osmotic stress in rat ventricular myocytes. Can J Physiol Pharmacol 2013; 91:686-92. [DOI: 10.1139/cjpp-2012-0408] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objective of this study was to investigate the mechanisms of increase in the efficacy of ATP-sensitive K+ channel (KATP) openings by hypo-osmotic stress. The whole-cell KATP currents (IK,ATP) stimulated by 100 μmol/L pinacidil, a K+ channel opening drug, were significantly augmented during hypo-osmotic stress (189 mOsmol/L) compared with normal conditions (303 mOsmol/L). The EC50 and Emax value for pinacidil-activated IK,ATP (measured at 0 mV) was 154 μmol/L and 844 pA, respectively, in normal solution and 16.6 μmol/L and 1266 pA, respectively, in hypo-osmotic solution. Augmentation of IK,ATP during hypo-osmotic stress was attenuated by wortmannin (50 μmol/L), an inhibitor of phosphatidylinositol 3- and 4-kinases, but not by (i) phalloidin (30 μmol/L), an actin filament stabilizer, (ii) the absence of Ca2+ from the internal and external solutions, and (iii) the presence of creatine phosphate (3 mmol/L), which affects creatine kinase regulation of the KATP channels. In the single-channel recordings, an inside-out patch was made after approximately 5 min exposure of the myocyte to hypo-osmotic solution. However, the IC50 value for ATP under such conditions was not different from that obtained in normal osmotic solution. In conclusion, hypo-osmotic stress could augment cardiac IK,ATP through intracellular mechanisms involving the phosphatidylinositol kinase pathway.
Collapse
Affiliation(s)
- Hirofumi Mitsuyama
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
| | - Hisashi Yokoshiki
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
| | - Yuki Irie
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
| | - Masaya Watanabe
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
| | - Kazuya Mizukami
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
| | - Hiroyuki Tsutsui
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
| |
Collapse
|
3
|
Irianto J, Swift J, Martins RP, McPhail GD, Knight MM, Discher DE, Lee DA. Osmotic challenge drives rapid and reversible chromatin condensation in chondrocytes. Biophys J 2013; 104:759-69. [PMID: 23442954 DOI: 10.1016/j.bpj.2013.01.006] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2012] [Revised: 08/20/2012] [Accepted: 01/07/2013] [Indexed: 02/02/2023] Open
Abstract
Changes in extracellular osmolality have been shown to alter gene expression patterns and metabolic activity of various cell types, including chondrocytes. However, mechanisms by which physiological or pathological changes in osmolality impact chondrocyte function remain unclear. Here we use quantitative image analysis, electron microscopy, and a DNase I assay to show that hyperosmotic conditions (>400 mOsm/kg) induce chromatin condensation, while hypoosmotic conditions (100 mOsm/kg) cause decondensation. Large density changes (p < 0.001) occur over a very narrow range of physiological osmolalities, which suggests that chondrocytes likely experience chromatin condensation and decondensation during a daily loading cycle. The effect of changes in osmolality on nuclear morphology (p < 0.01) and chromatin condensation (p < 0.001) also differed between chondrocytes in monolayer culture and three-dimensional agarose, suggesting a role for cell adhesion. The relationship between condensation and osmolality was accurately modeled by a polymer gel model which, along with the rapid nature of the chromatin condensation (<20 s), reveals the basic physicochemical nature of the process. Alterations in chromatin structure are expected to influence gene expression and thereby regulate chondrocyte activity in response to osmotic changes.
Collapse
Affiliation(s)
- Jerome Irianto
- Institute of Bioengineering, School of Engineering and Material Science, Queen Mary, University of London, London, United Kingdom.
| | | | | | | | | | | | | |
Collapse
|
4
|
Missan S, Shuba LM, Zhabyeyev P, McDonald TF. Osmotic modulation of slowly activating IKs in guinea-pig ventricular myocytes. Cardiovasc Res 2011; 91:429-36. [DOI: 10.1093/cvr/cvr074] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
5
|
Luo AT, Luo HY, Hu XW, Gao LL, Liang HM, Tang M, Hescheler J. Hyposmotic challenge modulates function of L-type calcium channel in rat ventricular myocytes through protein kinase C. Acta Pharmacol Sin 2010; 31:1438-46. [PMID: 20953210 DOI: 10.1038/aps.2010.112] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
AIM To study the effects and mechanisms by which hyposmotic challenge modulate function of L-type calcium current (I(Ca,L)) in rat ventricular myocytes. METHODS The whole-cell patch-clamp techniques were used to record I(Ca,L) in rat ventricular myocytes. RESULTS Hyposmotic challenge(∼220 mosmol/L) induced biphasic changes of I(Ca,L), a transient increase followed by a sustained decrease. I(Ca,L) increased by 19.1%±6.1% after short exposure (within 3 min) to hyposmotic solution. On the contrary, long hyposmotic challenge (10 min) decreased I(Ca,L) to 78.1%±11.0% of control, caused the inactivation of I(Ca,L), and shifted the steady-state inactivation curve of I(Ca,L) to the right. The decreased I(Ca,L) induced by hyposmotic swelling was reversed by isoproterenol or protein kinase A (PKA) activator foskolin. Hyposmotic swelling also reduced the stimulated I(Ca,L) by isoproterenol or foskolin. PKA inhibitor H-89 abolished swelling-induced transient increase of I(Ca,L), but did not affect the swelling-induced sustained decrease of I(Ca,L). NO donor SNAP and protein kinase G (PKG) inhibitor Rp-8-Br-PET-cGMPS did not interfere with swelling-induced biphasic changes of I(Ca,L). Protein kinase C (PKC) activator PMA decreased I(Ca,L) and hyposmotic solution with PMA reverted the decreased I(Ca,L) by PMA. PKC inhibitor BIM prevented the swelling-induced biphasic changes of I(Ca,L). CONCLUSION Hyposmotic challenge induced biphasic changes of I(Ca,L), a transient increase followed by a sustained decrease, in rat ventricular myocytes through PKC pathway, but not PKG pathway. PKA system could be responsible for the transient increase of I(Ca,L) during short exposure to hyposmotic solution.
Collapse
|
6
|
Piron J, Choveau FS, Amarouch MY, Rodriguez N, Charpentier F, Mérot J, Baró I, Loussouarn G. KCNE1-KCNQ1 osmoregulation by interaction of phosphatidylinositol-4,5-bisphosphate with Mg2+ and polyamines. J Physiol 2010; 588:3471-83. [PMID: 20660559 DOI: 10.1113/jphysiol.2010.195313] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
KCNQ1 osmosensitivity is of physiological and pathophysiological relevance in epithelial and cardiac cells, but the mechanism involved remains elusive. In COS-7 cells expressing the KCNE1-KCNQ1 fusion protein, extracellular hypoosmolarity and hyperosmolarity modify the channel biophysical parameters. These changes are consistent with hypoosmolarity increasing the level of membrane phosphatidylinositol-4,5-bisphosphate (PIP(2)), which in turn upregulates KCNE1-KCNQ1 channels. We showed that increasing PIP(2) levels with a water-soluble PIP(2) analogue prevented channel upregulation in hypoosmotic condition, suggesting a variation of the channel-PIP(2) interaction during channel osmoregulation. Furthermore, we showed that polyamines and Mg(2+), already known to tonically inhibit KCNQ channels by screening PIP(2) negative charges, are involved in the osmoregulatory process. Indeed, intracellular Mg(2+) removal and polyamines chelation inhibited the channel osmoregulation. Thus, the dilution of those cations during cell swelling might decrease channel inhibition and explain the channel upregulation by hypoosmolarity. To support this idea, we quantified the role of Mg(2+) in the osmodependent channel activity. Direct measurement of intracellular [Mg(2+)] variations during osmotic changes and characterization of the channel Mg(2+) sensitivity showed that Mg(2+) participates significantly to the osmoregulation. Using intracellular solutions that mimic the variation of Mg(2+) and polyamines, we were able to recapitulate the current amplitude variations in response to extracellular osmolarity changes. Altogether, these results support the idea of a modulation of the channel-PIP(2) interactions by Mg(2+) and polyamines during cell volume changes. It is likely that this mechanism applies to other channels that are sensitive to both osmolarity and PIP(2).
Collapse
Affiliation(s)
- Julien Piron
- INSERM U915, l'Institut du Thorax, 8 quai Moncousu, BP 70721, 44007 Nantes Cedex 1, France
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Regulation of human cardiac KCNQ1/KCNE1 channel by epidermal growth factor receptor kinase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:995-1001. [DOI: 10.1016/j.bbamem.2010.01.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 01/12/2010] [Accepted: 01/13/2010] [Indexed: 11/19/2022]
|
8
|
Finan JD, Guilak F. The effects of osmotic stress on the structure and function of the cell nucleus. J Cell Biochem 2010; 109:460-7. [PMID: 20024954 PMCID: PMC3616882 DOI: 10.1002/jcb.22437] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Osmotic stress is a potent regulator of the normal function of cells that are exposed to osmotically active environments under physiologic or pathologic conditions. The ability of cells to alter gene expression and metabolic activity in response to changes in the osmotic environment provides an additional regulatory mechanism for a diverse array of tissues and organs in the human body. In addition to the activation of various osmotically- or volume-activated ion channels, osmotic stress may also act on the genome via a direct biophysical pathway. Changes in extracellular osmolality alter cell volume, and therefore, the concentration of intracellular macromolecules. In turn, intracellular macromolecule concentration is a key physical parameter affecting the spatial organization and pressurization of the nucleus. Hyper-osmotic stress shrinks the nucleus and causes it to assume a convoluted shape, whereas hypo-osmotic stress swells the nucleus to a size that is limited by stretch of the nuclear lamina and induces a smooth, round shape of the nucleus. These behaviors are consistent with a model of the nucleus as a charged core/shell structure pressurized by uneven partition of macromolecules between the nucleoplasm and the cytoplasm. These osmotically-induced alterations in the internal structure and arrangement of chromatin, as well as potential changes in the nuclear membrane and pores are hypothesized to influence gene transcription and/or nucleocytoplasmic transport. A further understanding of the biophysical and biochemical mechanisms involved in these processes would have important ramifications for a range of fields including differentiation, migration, mechanotransduction, DNA repair, and tumorigenesis.
Collapse
Affiliation(s)
- John D Finan
- Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA
| | | |
Collapse
|
9
|
Angiotensin II type 1 receptor mediates partially hyposmotic-induced increase of I Ks current in guinea pig atrium. Pflugers Arch 2009; 458:837-49. [DOI: 10.1007/s00424-009-0669-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Accepted: 03/27/2009] [Indexed: 01/29/2023]
|
10
|
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.
Collapse
Affiliation(s)
- Sofia Hammami
- Department of Biology, University of Copenhagen, Denmark
| | | | | | | | | | | |
Collapse
|
11
|
Missan S, Qi J, Crack J, McDonald TF, Linsdell P. Regulation of wild-type and mutant KCNQ1/KCNE1 channels by tyrosine kinase. Pflugers Arch 2009; 458:471-80. [DOI: 10.1007/s00424-008-0634-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2008] [Revised: 11/27/2008] [Accepted: 12/29/2008] [Indexed: 11/28/2022]
|
12
|
Missan S, Linsdell P, McDonald TF. Involvement of tyrosine kinase in the hyposmotic stimulation of I Ks in guinea-pig ventricular myocytes. Pflugers Arch 2007; 456:489-500. [DOI: 10.1007/s00424-007-0424-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Revised: 10/24/2007] [Accepted: 12/06/2007] [Indexed: 11/30/2022]
|
13
|
Missan S, Linsdell P, McDonald TF. Role of kinases and G-proteins in the hyposmotic stimulation of cardiac IKs. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1641-52. [PMID: 16836976 DOI: 10.1016/j.bbamem.2006.05.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Revised: 05/19/2006] [Accepted: 05/30/2006] [Indexed: 12/16/2022]
Abstract
Exposure of cardiac myocytes to hyposmotic solution stimulates slowly-activating delayed-rectifying K(+) current (I(Ks)) via unknown mechanisms. In the present study, I(Ks) was measured in guinea-pig ventricular myocytes that were pretreated with modulators of cell signaling processes, and then exposed to hyposmotic solution. Pretreatment with compounds that (i) inhibit serine/threonine kinase activity (10-100 microM H89; 200 microM H8; 50 microM H7; 1 microM bisindolylmaleimide I; 10 microM LY294002; 50 microM PD98059), (ii) stimulate serine/threonine kinase activity (1-5 microM forskolin; 0.1 microM phorbol-12-myristate-13-acetate; 10 microM acetylcholine; 0.1 microM angiotensin II; 20 microM ATP), (iii) suppress G-protein activation (10 mM GDPbetaS), or (iv) disrupt the cytoskeleton (10 microM cytochalasin D), had little effect on the stimulation of I(Ks) by hyposmotic solution. In marked contrast, pretreatment with tyrosine kinase inhibitor tyrphostin A25 (20 microM) strongly attenuated both the hyposmotic stimulation of I(Ks) in myocytes and the hyposmotic stimulation of current in BHK cells co-expressing Ks channel subunits KCNQ1 and KCNE1. Since attenuation of hyposmotic stimulation was not observed in myocytes and cells pretreated with inactive tyrphostin A1, we conclude that TK has an important role in the response of cardiac Ks channels to hyposmotic solution.
Collapse
Affiliation(s)
- Sergey Missan
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
| | | | | |
Collapse
|
14
|
Missan S, Zhabyeyev P, Linsdell P, McDonald TF. Insensitivity of cardiac delayed-rectifier I(Kr) to tyrosine phosphorylation inhibitors and stimulators. Br J Pharmacol 2006; 148:724-31. [PMID: 16715119 PMCID: PMC1751861 DOI: 10.1038/sj.bjp.0706776] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The rapidly activating delayed-rectifying K+ current (I(Kr)) in heart cells is an important determinant of repolarisation, and decreases in its density are implicated in acquired and inherited long QT syndromes. The objective of the present study on I(Kr) in guinea-pig ventricular myocytes was to evaluate whether the current is acutely regulated by tyrosine phosphorylation. 2. Myocytes configured for ruptured-patch or perforated-patch voltage-clamp were depolarised with 200-ms steps to 0 mV for measurement of I(Kr) tail amplitude on repolarisations to -40 mV. 3. I(Kr) in both ruptured-patch and perforated-patch myocytes was only moderately (14-20%) decreased by 100 microM concentrations of protein tyrosine kinase (PTK) inhibitors tyrphostin A23, tyrphostin A25, and genistein. However, similar-sized decreases were induced by PTK-inactive analogues tyrphostin A1 and daidzein, suggesting that they were unrelated to inhibition of PTK. 4. Ruptured-patch and perforated-patch myocytes were also treated with promoters of tyrosine phosphorylation, including phosphotyrosyl phosphatase (PTP) inhibitor orthovanadate, exogenous c-Src PTK, and four receptor PTK activators (insulin, insulin-like growth factor-1, epidermal growth factor, and basic fibroblast growth factor). None of these treatments had a significant effect on the amplitude of I(Kr). 5. We conclude that Kr channels in guinea-pig ventricular myocytes are unlikely to be regulated by PTK and PTP.
Collapse
Affiliation(s)
- Sergey Missan
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
| | - Pavel Zhabyeyev
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
| | - Paul Linsdell
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
| | - Terence F McDonald
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
- Author for correspondence:
| |
Collapse
|
15
|
Missan S, Linsdell P, McDonald TF. Tyrosine kinase and phosphatase regulation of slow delayed-rectifier K+ current in guinea-pig ventricular myocytes. J Physiol 2006; 573:469-82. [PMID: 16581870 PMCID: PMC1779722 DOI: 10.1113/jphysiol.2005.104422] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The objective of this study was to investigate the involvement of tyrosine phosphorylation in the regulation of the cardiac slowly activating delayed-rectifier K(+) current (I(Ks)) that is important for action potential repolarization. Constitutive I(Ks) recorded from guinea-pig ventricular myocytes was suppressed by broad-spectrum tyrosine kinase (TK) inhibitors tyrphostin A23 (IC(50), 4.1+/-0.6 microm), tyrphostin A25 (IC(50), 12.1+/-2.1 microm) and genistein (IC(50), 64+/-4 microm), but was relatively insensitive to the inactive analogues tyrphostin A1, tyrphostin A63, daidzein and genistin. I(Ks) was unaffected by AG1478 (10 microm), an inhibitor of epidermal growth factor receptor TK, and was strongly suppressed by the Src TK inhibitor PP2 (10 microm) but not by the inactive analogue PP3 (10 microm). The results of experiments with forskolin, H89 and bisindolylmaleimide I indicate that the suppression of I(Ks) by TK inhibitors was not mediated via inhibition of (I(Ks)-stimulatory) protein kinases A and C. To evaluate whether the suppression was related to lowered tyrosine phosphorylation, myocytes were pretreated with TK inhibitors and then exposed to the phosphotyrosyl phosphatase inhibitor orthovanadate (1 mm). Orthovanadate almost completely reversed the suppression of I(Ks) induced by broad-spectrum TK inhibitors at concentrations around their IC(50) values. We conclude that basal I(Ks) is strongly dependent on tyrosine phosphorylation of Ks channel (or channel-regulatory) protein.
Collapse
Affiliation(s)
- Sergey Missan
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
| | | | | |
Collapse
|
16
|
Missan S, Zhabyeyev P, Dyachok O, Ogura T, McDonald TF. Inward-rectifier K+ current in guinea-pig ventricular myocytes exposed to hyperosmotic solutions. J Membr Biol 2005; 202:151-60. [PMID: 15798903 DOI: 10.1007/s00232-004-0726-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2004] [Accepted: 11/04/2004] [Indexed: 11/25/2022]
Abstract
Superfusion of heart cells with hyperosmotic solution causes cell shrinkage and inhibition of membrane ionic currents, including delayed-rectifer K+ currents. To determine whether osmotic shrinkage also inhibits inwardly-rectifying K+ current (I(K1)), guinea-pig ventricular myocytes in the perforated-patch or ruptured-patch configuration were superfused with a Tyrode's solution whose osmolarity (T) relative to isosmotic (1T) solution was increased to 1.3-2.2T by addition of sucrose. Hyperosmotic superfusate caused a rapid shrinkage that was accompanied by a negative shift in the reversal potential of Ba(2+)-sensitive I(K1), an increase in the amplitude of outward I(K1), and a steepening of the slope of the inward I(K1)-voltage (V) relation. The magnitude of these effects increased with external osmolarity. To evaluate the underlying changes in chord conductance (G(K1)) and rectification, G(K1)-V data were fitted with Boltzmann functions to determine maximal G(K1) (G(K1)max) and voltage at one-half G(K1)max (V(0.5)). Superfusion with hyperosmotic sucrose solutions led to significant increases in G(K1)max (e.g., 28 +/- 2% with 1.8T), and significant negative shifts in V(0.5) (e.g., -6.7 +/- 0.6 mV with 1.8T). Data from myocytes investigated under hyperosmotic conditions that do not induce shrinkage indicate that G(K1)max and V(0.5) were insensitive to hyperosmotic stress per se but sensitive to elevation of intracellular K+. We conclude that the effects of hyperosmotic sucrose solutions on I(K1) are related to shrinkage-induced concentrating of intracellular K+.
Collapse
Affiliation(s)
- S Missan
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, B3H 4H7, Canada
| | | | | | | | | |
Collapse
|
17
|
Ren Z, Baumgarten CM. Antagonistic regulation of swelling-activated Cl- current in rabbit ventricle by Src and EGFR protein tyrosine kinases. Am J Physiol Heart Circ Physiol 2005; 288:H2628-36. [PMID: 15681694 PMCID: PMC1305917 DOI: 10.1152/ajpheart.00992.2004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Regulation of swelling-activated Cl(-) current (I(Cl,swell)) is complex, and multiple signaling cascades are implicated. To determine whether protein tyrosine kinase (PTK) modulates I(Cl,swell) and to identify the PTK involved, we studied the effects of a broad-spectrum PTK inhibitor (genistein), selective inhibitors of Src (PP2, a pyrazolopyrimidine) and epidermal growth factor receptor (EGFR) kinase (PD-153035), and a protein tyrosine phosphatase (PTP) inhibitor (orthovanadate). I(Cl,swell) evoked by hyposmotic swelling was increased 181 +/- 17% by 100 microM genistein, and the genistein-induced current was blocked by the selective I(Cl,swell) blocker tamoxifen (10 microM). Block of Src with PP2 (10 microM) stimulated tamoxifen-sensitive I(Cl,swell) by 234 +/- 27%, mimicking genistein, whereas the inactive analog of PP2, PP3 (10 microM), had no effect. Moreover, block of PTP by orthovanadate (1 mM) inhibited I(Cl,swell) and prevented its stimulation by PP2. In contrast with block of Src, block of EGFR kinase with PD-153035 (20 nM) inhibited I(Cl,swell). Several lines of evidence argue that the PP2-stimulated current was I(Cl,swell): 1) the stimulation was volume dependent, 2) the current was blocked by tamoxifen, 3) the current outwardly rectified with both symmetrical and physiological Cl(-) gradients, and 4) the current reversed near the Cl(-) equilibrium potential. To rule out contributions of other currents, Cd(2+) (0.2 mM) and Ba(2+) (1 mM) were added to the bath. Surprisingly, Cd(2+) suppressed the decay of I(Cl,swell), and Cd(2+) plus Ba(2+) eliminated time-dependent currents between -100 and +100 mV. Nevertheless, these divalent ions did not eliminate I(Cl,swell) or prevent its stimulation by PP2. The results indicate that tyrosine phosphorylation controls I(Cl,swell), and regulation of I(Cl,swell) by the Src and EGFR kinase families of PTK is antagonistic.
Collapse
Affiliation(s)
- Zuojun Ren
- Department of Cardiology, China Medical University, Shenyang, Liaoning, People’s Republic of China; and Departments of
- Physiology and
| | - Clive M. Baumgarten
- Physiology and
- Internal Medicine (Cardiology) and Biomedical Engineering, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia
- Address for reprint requests and other correspondence: C. M. Baumgarten, Dept. of Physiology, Box 980551, Medical College of Virginia, Virginia Commonwealth Univ., 1101 E. Marshall St., Richmond, VA 23298 (E-mail:
)
| |
Collapse
|
18
|
Sims C, Harvey RD. Redox modulation of basal and beta-adrenergically stimulated cardiac L-type Ca(2+) channel activity by phenylarsine oxide. Br J Pharmacol 2004; 142:797-807. [PMID: 15172960 PMCID: PMC1575054 DOI: 10.1038/sj.bjp.0705845] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
1. Phenylarsine oxide (PAO) is commonly used to inhibit tyrosine phosphatase activity. However, PAO can affect a variety of different processes because of its ability to promote sulfhydryl oxidation. In the present study, we investigated the effects that PAO has on basal and beta-adrenergically stimulated L-type Ca(2+) channel activity in isolated cardiac myocytes. 2. Extracellular application of PAO transiently stimulated the basal L-type Ca(2+) channel activity, whereas it irreversibly inhibited protein kinase A (PKA)-dependent regulation of channel activity by isoproterenol, forskolin and 8-CPT-cAMP (8-p-chlorophenylthioadenosine 3',5'-cyclic monophosphate). PAO also inhibited channel activity irreversibly stimulated in the presence of adenosine 5'-(3-thiotriphosphate) tetralithium salt. 3. Neither the stimulatory nor the inhibitory effects of PAO were affected by the tyrosine kinase inhibitor lavendustin A, suggesting that tyrosine phosphorylation is not involved. 4. Extracellular application of the sulfhydryl-reducing agent dithiothreitol (DTT) antagonized both the stimulatory and inhibitory effects of PAO. Yet, following intracellular dialysis with DTT, only the inhibitory effect of PAO was antagonized. 5. The inhibitory effect of PAO was mimicked by intracellular, but not extracellular application of the membrane impermeant thiol oxidant 5,5'-dithio-bis(2-nitrobenzoic acid). 6. These results suggest that the stimulatory effect of PAO results from oxidation of sulfhydryl residues at an extracellular site and the inhibitory effect is due to redox regulation of an intracellular site that affects the response of the channel to PKA-dependent phosphorylation. It is concluded that the redox state of the cell may play a critical role in modulating beta-adrenergic responsiveness of the L-type Ca(2+) channel in cardiac myocytes.
Collapse
MESH Headings
- Animals
- Arsenicals/antagonists & inhibitors
- Arsenicals/pharmacology
- Calcium/metabolism
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/physiology
- Colforsin/pharmacology
- Cyclic AMP/analogs & derivatives
- Cyclic AMP/pharmacology
- Dithiothreitol/pharmacology
- Drug Evaluation, Preclinical/methods
- Electrophysiology
- Guinea Pigs
- Isoproterenol/pharmacology
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/pathology
- Myocytes, Cardiac/physiology
- Oxidation-Reduction/drug effects
- Phosphorylation/drug effects
- Protein Tyrosine Phosphatases/antagonists & inhibitors
- Protein Tyrosine Phosphatases/drug effects
- Protein Tyrosine Phosphatases/metabolism
- Protein-Tyrosine Kinases/antagonists & inhibitors
- Protein-Tyrosine Kinases/drug effects
- Receptors, Adrenergic, beta/drug effects
- Receptors, Adrenergic, beta/physiology
- Signal Transduction
- Thionucleotides/pharmacology
- Time Factors
Collapse
Affiliation(s)
- Carl Sims
- Department of Physiology and Biophysics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4970, U.S.A
| | - Robert D Harvey
- Department of Physiology and Biophysics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4970, U.S.A
- Author for correspondence:
| |
Collapse
|
19
|
Du XL, Gao Z, Lau CP, Chiu SW, Tse HF, Baumgarten CM, Li GR. Differential effects of tyrosine kinase inhibitors on volume-sensitive chloride current in human atrial myocytes: evidence for dual regulation by Src and EGFR kinases. ACTA ACUST UNITED AC 2004; 123:427-39. [PMID: 15024039 PMCID: PMC2217456 DOI: 10.1085/jgp.200409013] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
To determine whether protein tyrosine kinase (PTK) modulates volume-sensitive chloride current (ICl.vol) in human atrial myocytes and to identify the PTKs involved, we studied the effects of broad-spectrum and selective PTK inhibitors and the protein tyrosine phosphatase (PTP) inhibitor orthovanadate (VO4−3). ICl.vol evoked by hyposmotic bath solution (0.6-times isosmotic, 0.6T) was enhanced by genistein, a broad-spectrum PTK inhibitor, in a concentration-dependent manner (EC50 = 22.4 μM); 100 μM genistein stimulated ICl.vol by 122.4 ± 10.6%. The genistein-stimulated current was inhibited by DIDS (4,4′-diisothiocyanostilbene-2,2′-disulfonic acid, 150 μM) and tamoxifen (20 μM), blockers of ICl.vol. Moreover, the current augmented by genistein was volume dependent; it was abolished by hyperosmotic shrinkage in 1.4T, and genistein did not activate Cl− current in 1T. In contrast to the stimulatory effects of genistein, 100 μM tyrphostin A23 (AG 18) and A25 (AG 82) inhibited ICl.vol by 38.2 ± 4.9% and 40.9 ± 3.4%, respectively. The inactive analogs, daidzein and tyrphostin A63 (AG 43), did not alter ICl.vol. In addition, the PTP inhibitor VO4−3 (1 mM) reduced ICl.vol by 53.5 ± 4.5% (IC50 = 249.6 μM). Pretreatment with VO4−3 antagonized genistein-induced augmentation and A23- or A25-induced suppression of ICl.vol. Furthermore, the selective Src-family PTK inhibitor PP2 (5 μM) stimulated ICl.vol, mimicking genistein, whereas the selective EGFR (ErbB-1) kinase inhibitor tyrphostin B56 (AG 556, 25 μM) reduced ICl.vol, mimicking A23 and A25. The effects of both PP2 and B56 also were substantially antagonized by pretreatment with VO4−3. The results suggest that ICl.vol is regulated in part by the balance between PTK and PTP activity. Regulation is complex, however. Src and EGFR kinases, distinct soluble and receptor-mediated PTK families, have opposing effects on ICl.vol, and multiple target proteins are likely to be involved.
Collapse
Affiliation(s)
- Xin-Ling Du
- Institute of Cardiovascular Science and Medicine/Department of Medicine, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | | | | | | | | | | | | |
Collapse
|
20
|
Ogura T, Matsuda H, Shibamoto T, Imanishi S. Osmosensitive properties of rapid and slow delayed rectifier K+ currents in guinea-pig heart cells. Clin Exp Pharmacol Physiol 2003; 30:616-22. [PMID: 12940877 DOI: 10.1046/j.1440-1681.2003.03869.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. Changes in cell volume affect a variety of sarcolemmal transport processes in the heart. To study whether osmotically induced cell volume shrinkage has functional consequences for K+ channel activity, guinea-pig cardiac preparations were superfused with hyperosmotic Tyrode's solution (1.2-2-fold normal osmolality). Membrane currents and cell surface dimensions were measured from whole-cell patch-clamped ventricular myocytes and membrane potentials were recorded from isolated ventricular muscles and non-patched myocytes. 2. Hyperosmotic treatment of myocytes quickly (< 3 min to steady state) shrank cell volume (approximately 20% reduction in 1.5-fold hyperosmotic solution) and depressed the delayed rectifier K+ current (IK). Analysis using different activation protocols and a selective inhibitor (5 micro mol/L E4031) indicated that the IK inhibition was due to osmolality and cell volume-dependent changes in the two subtypes of the classical cardiac IK (rapidly activating IKr and slowly activating IKs); 1.5-fold hyperosmotic treatment depressed the amplitudes of IKr and IKs by approximately 30 and 50%, respectively. 3. Superfusion of muscles and myocytes with 1.5-fold hyperosmotic solution lengthened the action potentials by 14-17%. Hyperosmotic treatment also caused 6-7 mV hyperpolarization that is most likely due to a concentrating of intracellular K+. 4. The inhibition of IK helps explain the lengthening of action potentials observed in osmotically stressed heart cells. These results, together with the reported IK stimulation by hyposmotic cell swelling, provide further support for cell volume-sensitive properties of cardiac electrical activity.
Collapse
Affiliation(s)
- Toshitsugu Ogura
- Second Department of Physiology, Kanazawa Medical University, 1-1 Daigaku, Uchinada-machi, Kahoku-gun, Ishikawa-ken 920-0293, Japan.
| | | | | | | |
Collapse
|
21
|
Li GR, Zhang M, Satin LS, Baumgarten CM. Biphasic effects of cell volume on excitation-contraction coupling in rabbit ventricular myocytes. Am J Physiol Heart Circ Physiol 2002; 282:H1270-7. [PMID: 11893561 DOI: 10.1152/ajpheart.00946.2001] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We studied the effects of osmotic swelling on the components of excitation-contraction coupling in ventricular myocytes. Myocyte volume rapidly increased 30% in hyposmotic (0.6T) solution and was constant thereafter. Cell shortening transiently increased 31% after 4 min in 0.6T but then decreased to 68% of control after 20 min. In parallel, the L-type Ca(2+) current (I(Ca-L)) transiently increased 10% and then declined to 70% of control. Similar biphasic effects on shortening were observed under current clamp. In contrast, action potential duration was unchanged at 4 min but decreased to 72% of control after 20 min. Ca(2+) transients were measured with fura 2-AM. The emission ratio with excitation at 340 and 380 nm (f(340)/f(380)) decreased by 12% after 3 min in 0.6T, whereas shortening and I(Ca-L) increased at the same time. After 8 min, shortening, I(Ca-L), and the f(340)/f(380) ratio decreased 28, 25, and 59%, respectively. The results suggest that osmotic swelling causes biphasic changes in I(Ca-L) that contribute to its biphasic effects on contraction. In addition, swelling initially appears to reduce the Ca(2+) transient initiated by a given I(Ca-L), and later, both I(Ca-L) and the Ca(2+) transient are inhibited.
Collapse
Affiliation(s)
- Gui-Rong Li
- Department of Physiology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298, USA
| | | | | | | |
Collapse
|
22
|
Kubota T, Horie M, Takano M, Yoshida H, Otani H, Sasayama S. Role of KCNQ1 in the cell swelling-induced enhancement of the slowly activating delayed rectifier K(+) current. THE JAPANESE JOURNAL OF PHYSIOLOGY 2002; 52:31-9. [PMID: 12047800 DOI: 10.2170/jjphysiol.52.31] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Cell swelling enhances a slowly activating delayed rectifier K(+) current (I(Ks)) in cardiac cells. This investigation was undertaken to determine which of the two structural units reconstituting the I(Ks) channel, KCNQ1 (KvLQT1) and KCNE1 (minK/IsK), plays a key role in the cell swelling-induced I(Ks) enhancement and to dissect a possible involvement of tyrosine phosphorylation therein. KCNQ1 was transiently expressed alone or together with KCNE1 in a heterologous mammalian cell line. Two distinct whole-cell membrane currents were separately observed during the exposure of transfected cells to various degrees of hyposmotic solutions. A hyposmotic challenge (0.7 times control osmolarity) resulted in about a twofold increase not only in the heteromeric KCNQ1/KCNE1, but also in the homomeric KCNQ1 channel currents. There was no significant difference in the incremental ratio of current amplitude in response to hyposmotic stress between the two KCNQ1-related currents, and the cells expressing the heteromeric channels swelled less than those with the homomeric channels or without the exogenous ones. The cell swelling-induced I(Ks) enhancement was not affected by a protein tyrosine kinase (PTK) inhibitor, by genistein (50 microM), or by an inhibitor of phosphotyrosine phosphatase (PTP), orthovanadate (500 microM), or a nonhydrolyzable ATP analogue, AMP-PNP (5 mM). Taken together, it is very likely that KCNQ1 might primarily participate in the I(Ks) enhancement by osmotic cell swelling. The obligatory dependence of the I(Ks) augmentation on PTK activity remained to be demonstrated, at least, in this expression system.
Collapse
Affiliation(s)
- Tomoyuki Kubota
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine, Kyoto, 606-8057 Japan
| | | | | | | | | | | |
Collapse
|
23
|
Pascarel C, Brette F, Le Guennec JY. Enhancement of the T-type calcium current by hyposmotic shock in isolated guinea-pig ventricular myocytes. J Mol Cell Cardiol 2001; 33:1363-9. [PMID: 11437542 DOI: 10.1006/jmcc.2000.1399] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is known that swelling and shrinkage of cardiac cells can modulate their electrical activity. However, the effects of osmotic manipulation on cardiac T-type calcium current (I(CaT)) has not been previously reported. In this study, we have examined the effects of cell swelling on I(CaT), using the whole cell patch clamp configuration. Isolated guinea-pig ventricular myocytes were swollen by an external hypotonic challenge (0.7 T). We found that I(CaT)is enhanced during a hypotonic shock. This current has been determined to be the T type calcium current since it is rapidly activated and inactivated, its threshold was at negative potentials and was blocked by 40 microm Ni2+. Disruption of microfilaments by cytochalasin D and of microtubules by colchicine prevented the activation of I(CaT)during cell swelling. Taxol had no effect. These results indicate that I(CaT)is increased during cell swelling and this effect needs an intact cytoskeleton.
Collapse
Affiliation(s)
- C Pascarel
- Centre de Recherche Biologique, Chemin de Montifault, Baugy, 18800, France
| | | | | |
Collapse
|
24
|
Brette F, Calaghan SC, Lappin S, White E, Colyer J, Le Guennec JY. Biphasic effects of hyposmotic challenge on excitation-contraction coupling in rat ventricular myocytes. Am J Physiol Heart Circ Physiol 2000; 279:H1963-71. [PMID: 11009486 DOI: 10.1152/ajpheart.2000.279.4.h1963] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of short (1 min) and long (7-10 min) exposure to hyposmotic solution on excitation-contraction coupling in rat ventricular myocytes were studied. After short exposure, the action potential duration at 90% repolarization (APD(90)), the intracellular Ca(2+) concentration ([Ca(2+)](i)) transient amplitude, and contraction increased, whereas the L-type Ca(2+) current (I(Ca, L)) amplitude decreased. Fractional sarcoplasmic reticulum (SR) Ca(2+) release increased but SR Ca(2+) load did not. After a long exposure, I(Ca,L), APD(90), [Ca(2+)](i) transient amplitude, and contraction decreased. The abbreviation of APD(90) was partially reversed by 50 microM DIDS, which is consistent with the participation of Cl(-) current activated by swelling. After 10-min exposure to hyposmotic solution in cells labeled with di-8-aminonaphthylethenylpyridinium, t-tubule patterning remained intact, suggesting the loss of de-t-tubulation was not responsible for the fall in I(Ca,L). After long exposure, Ca(2+) load of the SR was not increased, and swelling had no effect on the site-specific phosphorylation of phospholamban, but fractional SR Ca(2+) release was depressed. The initial positive inotropic response to hyposmotic challenge may be accounted for by enhanced coupling between Ca(2+) entry and release. The negative inotropic effect of prolonged exposure can be accounted for by shortening of the action potential duration and a fall in the I(Ca,L) amplitude.
Collapse
Affiliation(s)
- F Brette
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9NQ, United Kingdom
| | | | | | | | | | | |
Collapse
|
25
|
Cazorla O, Pascarel C, Brette F, Le Guennec JY. Modulation of ions channels and membrane receptors activities by mechanical interventions in cardiomyocytes: possible mechanisms for mechanosensitivity. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1999; 71:29-58. [PMID: 10070211 DOI: 10.1016/s0079-6107(98)00036-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- O Cazorla
- Laboratoire de Physiologie des Cellules Cardiaques et Vasculaires, CNRS UMR 6542, Faculté des Sciences, Tours, France
| | | | | | | |
Collapse
|