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Weisbrod D. Small and Intermediate Calcium Activated Potassium Channels in the Heart: Role and Strategies in the Treatment of Cardiovascular Diseases. Front Physiol 2020; 11:590534. [PMID: 33329039 PMCID: PMC7719780 DOI: 10.3389/fphys.2020.590534] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 10/02/2020] [Indexed: 12/11/2022] Open
Abstract
Calcium-activated potassium channels are a heterogeneous family of channels that, despite their different biophysical characteristics, structures, and pharmacological signatures, play a role of transducer between the ubiquitous intracellular calcium signaling and the electric variations of the membrane. Although this family of channels was extensively described in various excitable and non-excitable tissues, an increasing amount of evidences shows their functional role in the heart. This review aims to focus on the physiological role and the contribution of the small and intermediate calcium-activated potassium channels in cardiac pathologies.
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Fan X, Yu Y, Lan H, Ou X, Yang L, Li T, Cao J, Zeng X, Li M. Ca2+/Calmodulin-Dependent Protein Kinase II (CaMKII) Increases Small-Conductance Ca2+-Activated K+ Current in Patients with Chronic Atrial Fibrillation. Med Sci Monit 2018; 24:3011-3023. [PMID: 29737974 PMCID: PMC5963316 DOI: 10.12659/msm.909684] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Background Increased small-conductance Ca2+-activated K+ current (SK), abnormal intracellular Ca2+ handling, and enhanced expression and activity of Ca2+/calmodulin-dependent protein kinase II (CaMKII) have been found in clinical and/or experimental models of atrial fibrillation (AF), but the cumulative effect of these phenomena and their mechanisms in AF are still unclear. This study aimed to test the hypothesis that CaMKII increases SK current in human chronic AF. Material/Methods Right atrial appendage tissues from patients with either sinus rhythm (SR) or AF and neonatal rat atrial myocytes were used. Patch clamp, qRT-PCR, and Western blotting techniques were used to perform the study. Results Compared to SR, the apamin-sensitive SK current (IKAS) was significantly increased, but the mRNA and protein levels of SK1, SK2, and SK3 were significantly decreased. In AF, the steady-state Ca2+ response curve of IKAS was shifted leftward and the [Ca2+]i level was significantly increased. CaMKII inhibitors (KN-93 or autocamtide-2-related inhibitory peptide (AIP)) reduced the IKAS in both AF and SR. The inhibitory effect of KN-93 or AIP on IKAS was greater in AF than in SR. The expression levels of calmodulin, CaMKII, and autophosphorylated CaMKII at Thr287 (but not at Thr286) were significantly increased in AF. Furthermore, KN-93 inhibited the expression of (Thr287)p-CaMKII and SK2 in neonatal rat atrial myocytes. Conclusions SK current is increased via the enhanced activation of CaMKII in patients with AF. This finding may explain the difference between SK current and channels expression in AF, and thus may provide a therapeutic target for AF.
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Affiliation(s)
- Xuehui Fan
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Yiyan Yu
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Huan Lan
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Xianhong Ou
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Lijie Yang
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Tao Li
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Jiming Cao
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Xiaorong Zeng
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
| | - Miaoling Li
- Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China (mainland)
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Coyle D, O'Donnell AM, Puri P. Altered distribution of small-conductance calcium-activated potassium channel SK3 in Hirschsprung's disease. J Pediatr Surg 2015; 50:1659-64. [PMID: 25783396 DOI: 10.1016/j.jpedsurg.2015.01.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 01/22/2015] [Indexed: 12/23/2022]
Abstract
PURPOSE SK3 channels are voltage-independent Ca(2+)-dependent K(+) channels that play a key role in regulating smooth muscle membrane potential during purinergic inhibitory neurotransmission in the colon. Dysmotility problems are common after a properly performed pull-through operation for Hirschsprung's disease (HSCR). We hypothesised that ganglionic bowel just proximal to the transition zone is abnormal and designed this study to investigate SK3 channel expression in HSCR. METHODS Entire resected bowel specimens were collected at the time of pull-through surgery for HSCR (n=6). Control colonic specimens were obtained at the time of colostomy closure in patients following anorectoplasty (n=6). SK3 protein expression was assessed qualitatively using immunofluorescence with confocal microscopy and quantitatively using western blot (WB) analysis. RESULTS Positive SK3 immunofluorescence was seen in the mucosa and in all three smooth muscle layers and the myenteric plexus in control specimens. SK3 immunofluorescence co-localised with PDGFRα. A band was detected at ~70kDa on WB. SK3 protein expression was barely detectable in aganglionic tissue and markedly reduced in the ganglionic bowel of 3 patients with HSCR compared to controls. CONCLUSION Decreased SK3 expression in ganglionic bowel may explain the basis of persistent bowel symptoms in some patients following a properly performed pull-through operation for HSCR.
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Affiliation(s)
- David Coyle
- National Children's Research Centre, Our Lady's Children's Hospital, Crumlin, Dublin, Ireland
| | - Anne Marie O'Donnell
- National Children's Research Centre, Our Lady's Children's Hospital, Crumlin, Dublin, Ireland
| | - Prem Puri
- National Children's Research Centre, Our Lady's Children's Hospital, Crumlin, Dublin, Ireland.
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Mizukami K, Yokoshiki H, Mitsuyama H, Watanabe M, Tenma T, Takada S, Tsutsui H. Small-conductance Ca2+-activated K+ current is upregulated via the phosphorylation of CaMKII in cardiac hypertrophy from spontaneously hypertensive rats. Am J Physiol Heart Circ Physiol 2015; 309:H1066-74. [DOI: 10.1152/ajpheart.00825.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 08/12/2015] [Indexed: 01/09/2023]
Abstract
Left ventricular hypertrophy is associated with an increased risk of ventricular arrhythmias. However, the underlying molecular basis is poorly understood. It has been reported that small-conductance Ca2+-activated K+ (SK) channels are involved in the pathogenesis of ventricular arrhythmias in heart failure. The present study aimed to test the hypothesis that SK channel activity is increased via the Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent pathway in hypertensive cardiac hypertrophy. Normotensive Wistar-Kyoto (WKY) rats and spontaneous hypertensive rats (SHRs) were used. Whole cell membrane currents were recorded in isolated ventricular myocytes by the patch-clamp method, and apamin-sensitive K+ current ( IKAS), which is inhibited by apamin (100 nM), an SK channel blocker, was evaluated. IKAS at 40 mV was present in SHRs, whereas it was hardly detectable in WKY rats (0.579 ± 0.046 vs. 0.022 ± 0.062 pA/pF, both n = 6, P < 0.05). IKAS was almost completely abolished by 1 μM KN-93, a CaMKII inhibitor, in SHRs. Optical recordings of left ventricular anterior wall action potentials revealed that apamin prolonged the late phase of repolarization only in SHRs. Western blot analysis of SK channel protein isoforms demonstrated that SK2 was significantly increased in SHRs compared with WKY rats (SK2/GAPDH: 0.66 ± 0.07 vs. 0.40 ± 0.02, both n = 6, P < 0.05), whereas SK1 and SK3 did not differ between groups. In addition, autophosphorylated CaMKII was significantly increased in SHRs (phosphorylated CaMKII/GAPDH: 0.80 ± 0.06 vs. 0.58 ± 0.06, both n = 6, P < 0.05) despite a comparable total amount of CaMKII between groups. In conclusion, SK channels are upregulated via the enhanced activation of CaMKII in cardiac hypertrophy in SHRs.
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Affiliation(s)
- Kazuya Mizukami
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Hisashi Yokoshiki
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Hirofumi Mitsuyama
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Masaya Watanabe
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Taro Tenma
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Shingo Takada
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Hiroyuki Tsutsui
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
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Lee JY, Ko EJ, Ahn KD, Kim S, Rhee PL. The role of K⁺ conductances in regulating membrane excitability in human gastric corpus smooth muscle. Am J Physiol Gastrointest Liver Physiol 2015; 308:G625-33. [PMID: 25591864 PMCID: PMC4385896 DOI: 10.1152/ajpgi.00220.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 01/12/2015] [Indexed: 01/31/2023]
Abstract
Changes in resting membrane potential (RMP) regulate membrane excitability. K(+) conductance(s) are one of the main factors in regulating RMP. The functional role of K(+) conductances has not been studied the in human gastric corpus smooth muscles (HGCS). To examine the role of K(+) channels in regulation of RMP in HGCS we employed microelectrode recordings, patch-clamp, and molecular approaches. Tetraethylammonium and charybdotoxin did not affect the RMP, suggesting that BK channels are not involved in regulating RMP. Apamin, a selective small conductance Ca(2+)-activated K(+) channel (SK) blocker, did not show a significant effect on the membrane excitability. 4-Aminopyridine, a Kv channel blocker, caused depolarization and increased the duration of slow wave potentials. 4-Aminopyridine also inhibited a delayed rectifying K(+) current in isolated smooth muscle cells. End-product RT-PCR gel detected Kv1.2 and Kv1.5 in human gastric corpus muscles. Glibenclamide, an ATP-sensitive K(+) channel (KATP) blocker, did not induce depolarization, but nicorandil, a KATP opener, hyperpolarized HGCS, suggesting that KATP are expressed but not basally activated. Kir6.2 transcript, a pore-forming subunit of KATP was expressed in HGCS. A low concentration of Ba(2+), a Kir blocker, induced strong depolarization. Interestingly, Ba(2+)-sensitive currents were minimally expressed in isolated smooth muscle cells under whole-cell patch configuration. KCNJ2 (Kir2.1) transcript was expressed in HGCS. Unique K(+) conductances regulate the RMP in HGCS. Delayed and inwardly rectifying K(+) channels are the main candidates in regulating membrane excitability in HGCS. With the development of cell dispersion techniques of interstitial cells, the cell-specific functional significance will require further analysis.
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Affiliation(s)
| | - Eun-ju Ko
- 2Samsung Biomedical Research Institute and
| | - Ki Duck Ahn
- 3Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Sung Kim
- 3Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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Mutafova-Yambolieva VN, Durnin L. The purinergic neurotransmitter revisited: a single substance or multiple players? Pharmacol Ther 2014; 144:162-91. [PMID: 24887688 PMCID: PMC4185222 DOI: 10.1016/j.pharmthera.2014.05.012] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 05/23/2014] [Indexed: 12/20/2022]
Abstract
The past half century has witnessed tremendous advances in our understanding of extracellular purinergic signaling pathways. Purinergic neurotransmission, in particular, has emerged as a key contributor in the efficient control mechanisms in the nervous system. The identity of the purine neurotransmitter, however, remains controversial. Identifying it is difficult because purines are present in all cell types, have a large variety of cell sources, and are released via numerous pathways. Moreover, studies on purinergic neurotransmission have relied heavily on indirect measurements of integrated postjunctional responses that do not provide direct information for neurotransmitter identity. This paper discusses experimental support for adenosine 5'-triphosphate (ATP) as a neurotransmitter and recent evidence for possible contribution of other purines, in addition to or instead of ATP, in chemical neurotransmission in the peripheral, enteric and central nervous systems. Sites of release and action of purines in model systems such as vas deferens, blood vessels, urinary bladder and chromaffin cells are discussed. This is preceded by a brief discussion of studies demonstrating storage of purines in synaptic vesicles. We examine recent evidence for cell type targets (e.g., smooth muscle cells, interstitial cells, neurons and glia) for purine neurotransmitters in different systems. This is followed by brief discussion of mechanisms of terminating the action of purine neurotransmitters, including extracellular nucleotide hydrolysis and possible salvage and reuptake in the cell. The significance of direct neurotransmitter release measurements is highlighted. Possibilities for involvement of multiple purines (e.g., ATP, ADP, NAD(+), ADP-ribose, adenosine, and diadenosine polyphosphates) in neurotransmission are considered throughout.
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Affiliation(s)
| | - Leonie Durnin
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, United States
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Ni Y, Wang T, Zhuo X, Song B, Zhang J, Wei F, Bai H, Wang X, Yang D, Gao L, Ma A. Bisoprolol reversed small conductance calcium-activated potassium channel (SK) remodeling in a volume-overload rat model. Mol Cell Biochem 2013; 384:95-103. [PMID: 23975505 DOI: 10.1007/s11010-013-1785-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 08/09/2013] [Indexed: 11/27/2022]
Abstract
A recent study indicated that apamin-sensitive current (I KAS, mediated by apamin-sensitive small conductance calcium-activated potassium channels subunits) density significantly increased in heart failure and led to recurrent spontaneous ventricular fibrillation. While the underlying molecular correlation with SK channels is still undetermined, we hypothesized that they are remodeled in HF and that bisoprolol could reverse the remodeling. Volume-overload models were created on male Sprague-Dawley rats by producing an abdominal arteriovenous fistula. Confocal microscopy, quantitative real-time PCR, and western blot were performed to investigate the expression of SK channels and observe the influence of β-blocker bisoprolol on the expression of SK channels I KAS, and the effect of bisoprolol on I KAS and the sensitivity of I KAS to [Ca(2+)]i at single isolated cells were also explored using whole-cell patch clamp techniques. SK channels were remodeled in HF rats, displaying the significant increase of SK1 and SK3 channel expression. After the treatment of HF rats with bisoprolol, the expression of SK1 and SK3 channels was significantly downregulated, and bisoprolol effectively downregulated I KAS density as well as the sensitivity of I KAS to [Ca(2+)]i. Our data indicated that the expression of SK1 and SK3 increased in HF. Bisoprolol effectively attenuated the change and downregulated I KAS density as well as the sensitivity of I KAS to [Ca(2+)]i.
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Affiliation(s)
- Yajuan Ni
- Department of Cardiovascular Medicine, Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education, First Affiliated Hospital of Xi'an Jiaotong University School of Medicine, No. 277, West Yanta Road, Xi'an, 710061, Shaanxi, China
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8
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He XD, Goyal RK. CaMKII inhibition hyperpolarizes membrane and blocks nitrergic IJP by closing a Cl(-) conductance in intestinal smooth muscle. Am J Physiol Gastrointest Liver Physiol 2012; 303:G240-6. [PMID: 22538403 PMCID: PMC3404568 DOI: 10.1152/ajpgi.00102.2012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The ionic basis of nitrergic "slow'" inhibitory junction potential (sIJP) is not fully understood. The purpose of the present study was to determine the nature and the role of calmodulin-dependent protein kinase II (CaMKII)-dependent ion conductance in nitrergic neurotransmission at the intestinal smooth muscle neuromuscular junction. Studies were performed in guinea pig ileum. The modified Tomita bath technique was used to induce passive hyperpolarizing electrotonic potentials (ETP) and membrane potential change due to sIJP or drug treatment in the same cell. Changes in membrane potential and ETP were recorded in the same smooth muscle cell, using sharp microelectrode. Nitrergic IJP was elicited by electrical field stimulation in nonadrenergic, noncholinergic conditions and chemical block of purinergic IJP. Modification of ETP during hyperpolarization reflected active conductance change in the smooth muscle. Nitrergic IJP was associated with decreased membrane conductance. The CAMKII inhibitor KN93 but not KN92, the Cl(-) channel blocker niflumic acid (NFA), and the K(ATP)-channel opener cromakalim hyperpolarized the membrane. However, KN93 and NFA were associated with decreased and cromakalim was associated with increased membrane conductance. After maximal NFA-induced hyperpolarization, hyperpolarization associated with KN93 or sIJP was not seen, suggesting a saturation block of the Cl(-) channel signaling. These studies suggest that inhibition of CaMKII-dependent Cl(-) conductance mediates nitrergic sIJP by causing maximal closure of the Cl(-) conductance.
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Affiliation(s)
- Xue-Dao He
- Center for Swallowing and Motility Disorders, Veterans Affairs Boston HealthCare System and Harvard Medical School, Boston, Massachusetts
| | - Raj K. Goyal
- Center for Swallowing and Motility Disorders, Veterans Affairs Boston HealthCare System and Harvard Medical School, Boston, Massachusetts
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Pharmacological characterization of uracil nucleotide-preferring P2Y receptors modulating intestinal motility: a study on mouse ileum. Purinergic Signal 2011; 8:275-85. [PMID: 22102167 DOI: 10.1007/s11302-011-9281-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 11/07/2011] [Indexed: 01/08/2023] Open
Abstract
We investigated the possible modulation of the intestinal contractility by uracil nucleotides (UTP and UDP), using as model the murine small intestine. Contractile activity of a mouse ileum longitudinal muscle was examined in vitro as changes in isometric tension. Transcripts encoding for uracil-sensitive receptors was investigated by RT-PCR. UDP induced muscular contractions, sensitive to PPADS, suramin, or MRS 2578, P2Y(6) receptor antagonist, and mimicked by PSB 0474, P2Y(6)-receptor agonist. UTP induced biphasic effects characterized by an early inhibition of the spontaneous contractile activity followed by muscular contraction. UTP excitatory effects were antagonized by PPADS, suramin, but not by MRS 2578, whilst the inhibitory effects were antagonized by PPADS but not by suramin or MRS 2578. UTPγS, P2Y(2)/(4) receptor agonist but not 2-thio-UTP, P2Y(2) receptor agonist, mimicked UTP effects. The inhibitory effects induced by UTP was abolished by ATP desensitization and increased by extracellular acidification. UDP or UTP responses were insensitive to TTX, atropine, or L-NAME antagonized by U-73122, inhibitor of phospholipase C (PLC) and preserved in the presence of nifedipine or low Ca(2+) solution. Transcripts encoding the uracil nucleotide-preferring receptors were expressed in mouse ileum. Functional postjunctional uracil-sensitive receptors are present in the longitudinal muscle of the mouse ileum. Activation of P2Y(6) receptors induces muscular contraction, whilst activation of P2Y(4) receptors leads to inhibition of the contractile activity. Indeed, the presence of atypical UTP-sensitive receptors leading to muscular contraction is suggested. All uracil-sensitive receptors are linked to the PLC pathway.
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Lim D, Kim NK, Park HS, Lee SH, Cho YM, Oh SJ, Kim TH, Kim H. Identification of candidate genes related to bovine marbling using protein-protein interaction networks. Int J Biol Sci 2011; 7:992-1002. [PMID: 21912507 PMCID: PMC3164149 DOI: 10.7150/ijbs.7.992] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 08/08/2011] [Indexed: 11/05/2022] Open
Abstract
Complex traits are determined by the combined effects of many loci and are affected by gene networks or biological pathways. Systems biology approaches have an important role in the identification of candidate genes related to complex diseases or traits at the system level. The present study systemically analyzed genes associated with bovine marbling score and identified their relationships. The candidate nodes were obtained using MedScan text-mining tools and linked by protein-protein interaction (PPI) from the Human Protein Reference Database (HPRD). To determine key node of marbling, the degree and betweenness centrality (BC) were used. The hub nodes and biological pathways of our network are consistent with the previous reports about marbling traits, and also suggest unknown candidate genes associated with intramuscular fat. Five nodes were identified as hub genes, which was consistent with the network analysis using quantitative reverse-transcription PCR (qRT-PCR). Key nodes of the PPI network have positive roles (PPARγ, C/EBPα, and RUNX1T1) and negative roles (RXRA, CAMK2A) in the development of intramuscular fat by several adipogenesis-related pathways. This study provides genetic information for identifying candidate genes for the marbling trait in bovine.
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Affiliation(s)
- Dajeong Lim
- Division of Animal Genomics and Bioinformatics, National Institute of Animal Science, Rural Development Administration, Suwon, Republic of Korea
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11
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Perrino BA. Regulation of gastrointestinal motility by Ca2+/calmodulin-stimulated protein kinase II. Arch Biochem Biophys 2011; 510:174-81. [PMID: 21443856 DOI: 10.1016/j.abb.2011.03.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 03/15/2011] [Accepted: 03/21/2011] [Indexed: 12/30/2022]
Abstract
Gastrointestinal (GI) motility ultimately depends upon the contractile activity of the smooth muscle cells of the tunica muscularis. Integrated functioning of multiple tissues and cell types, including enteric neurons and interstitial cells of Cajal (ICC) is necessary to generate coordinated patterns of motor activity that control the movement of material through the digestive tract. The neurogenic mechanisms that govern GI motility patterns are superimposed upon intrinsic myogenic mechanisms regulating smooth muscle cell excitability. Several mechanisms regulate smooth muscle cell responses to neurogenic inputs, including the multifunctional Ca(2+)/calmodulin-stimulated protein kinase II (CaMKII). CaMKII can be activated by Ca(2+) transients from both extracellular and intracellular sources. Prolonging the activities of Ca(2+)-sensitive K(+) channels in the plasma membrane of GI smooth muscle cells is an important regulatory mechanism carried out by CaMKII. Phospholamban (PLN) phosphorylation by CaMKII activates the sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA), increasing both the rate of Ca(2+) clearance from the myoplasm and the frequency of localized Ca(2+) release events from intracellular stores. Overall, CaMKII appears to moderate GI smooth muscle cell excitability. Finally, transcription factor activities may be facilitated by the neutralization of HDAC4 by CaMKII phosphorylation, which may contribute to the phenotypic plasticity of GI smooth muscle cells.
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Affiliation(s)
- Brian A Perrino
- Department of Physiology and Cell Biology, Center of Biomedical Research Excellence, University of Nevada School of Medicine, Reno, 89557, USA.
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12
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Hwang SJ, Durnin L, Dwyer L, Rhee PL, Ward SM, Koh SD, Sanders KM, Mutafova-Yambolieva VN. β-nicotinamide adenine dinucleotide is an enteric inhibitory neurotransmitter in human and nonhuman primate colons. Gastroenterology 2011; 140:608-617.e6. [PMID: 20875415 PMCID: PMC3031738 DOI: 10.1053/j.gastro.2010.09.039] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 08/03/2010] [Accepted: 09/17/2010] [Indexed: 12/25/2022]
Abstract
BACKGROUND & AIMS An important component of enteric inhibitory neurotransmission is mediated by a purine neurotransmitter, such as adenosine 5'-triphosphate (ATP), binding to P2Y1 receptors and activating small conductance K(+) channels. In murine colon β-nicotinamide adenine dinucleotide (β-NAD) is released with ATP and mimics the pharmacology of inhibitory neurotransmission better than ATP. Here β-NAD and ATP were compared as possible inhibitory neurotransmitters in human and monkey colons. METHODS A small-volume superfusion assay and high-pressure liquid chromatography with fluorescence detection were used to evaluate spontaneous and nerve-evoked overflow of β-NAD, ATP, and metabolites. Postjunctional responses to nerve stimulation, β-NAD and ATP were compared using intracellular membrane potential and force measurements. Effects of β-NAD on smooth muscle cells (SMCs) were recorded by patch clamp. P2Y receptor transcripts were assayed by reverse transcription polymerase chain reaction. RESULTS In contrast to ATP, overflow of β-NAD evoked by electrical field stimulation correlated with stimulation frequency and was diminished by the neurotoxins, tetrodotoxin, and ω-conotoxin GVIA. Inhibitory junction potentials and responses to exogenous β-NAD, but not ATP, were blocked by P2Y receptor antagonists suramin, pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate (PPADS), 2'-deoxy-N6-methyladenosine 3',5'-bisphosphate (MRS 2179), and (1R,2S,4S,5S)-4-[2-Iodo-6-(methylamino)-9H-purin-9-yl]-2-(phosphonooxy)bicyclo[3.1.0]hexane-1-methanol dihydrogen phosphate ester tetraammonium salt (MRS 2500). β-NAD activated nonselective cation currents in SMCs, but failed to activate outward currents. CONCLUSIONS β-NAD meets the criteria for a neurotransmitter better than ATP in human and monkey colons and therefore may contribute to neural regulation of colonic motility. SMCs are unlikely targets for inhibitory purine neurotransmitters because dominant responses of SMCs were activation of net inward, rather than outward, current.
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Affiliation(s)
- Sung Jin Hwang
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557
| | - Leonie Durnin
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557
| | - Laura Dwyer
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557
| | - Poong-Lyul Rhee
- Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 135-710, South Korea
| | - Sean M. Ward
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557
| | - Sang Don Koh
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557
| | - Kenton M. Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557
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Subtype-specific reduction of voltage-gated calcium current in medium-sized dorsal root ganglion neurons after painful peripheral nerve injury. Neuroscience 2011; 179:244-55. [PMID: 21277351 DOI: 10.1016/j.neuroscience.2011.01.049] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Revised: 01/08/2011] [Accepted: 01/23/2011] [Indexed: 11/23/2022]
Abstract
Sensory neurons express a variety of voltage-gated Ca2+ channel subtypes, but reports differ on their proportionate representation, and the effects of painful nerve injury on each subtype are not established. We compared levels of high-voltage activated currents in medium-sized (30-40 μm) dorsal root ganglion neurons dissociated from control animals and those subjected to spinal nerve ligation, using sequential application of semiselective channel blockers (nisoldipine for L-type, SNX-111 or ω-conotoxin GVIA for N-type, agatoxin IVA or ω-conotoxin MVIIC for P/Q-type, and SNX-482 for a component of R-type) during either square wave depolarizations or action potential waveform voltage commands. Using sequential administration of multiple blockers, proportions of total Ca2+ current attributable to different subtypes and the effect of injury depended on the sequence of blocker administration and type of depolarization command. Overall, however, N-type and L-type currents comprised the dominant components of ICa in sensory neurons under control conditions, and these subtypes showed the greatest loss of current following injury (L-type 26-71% loss, N-type 0-51% loss). Further exploration of N-type current identified by its sensitivity to ω-conotoxin GVIA applied alone showed that injury reduced the peak N-type current during step depolarization by 68% and decreased the total charge entry during action potential waveform stimulation by 44%. Isolation of N-type current by blockade of all other subtypes demonstrated a 50% loss with injury, and also revealed an injury-related rightward shift in the activation curve. Non-stationary noise analyses of N-type current in injured neurons revealed unitary channel current and number of channels that were not different from control, which indicates that injury-induced loss of current is due to a decrease in channel open probability. Our findings suggest that diminished Ca2+ influx through N-type and L-type channels may contribute to sensory neuron dysfunction and pain after nerve injury.
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14
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Abstract
The sarcoplasmic reticulum (SR) of smooth muscles presents many intriguing facets and questions concerning its roles, especially as these change with development, disease, and modulation of physiological activity. The SR's function was originally perceived to be synthetic and then that of a Ca store for the contractile proteins, acting as a Ca amplification mechanism as it does in striated muscles. Gradually, as investigators have struggled to find a convincing role for Ca-induced Ca release in many smooth muscles, a role in controlling excitability has emerged. This is the Ca spark/spontaneous transient outward current coupling mechanism which reduces excitability and limits contraction. Release of SR Ca occurs in response to inositol 1,4,5-trisphosphate, Ca, and nicotinic acid adenine dinucleotide phosphate, and depletion of SR Ca can initiate Ca entry, the mechanism of which is being investigated but seems to involve Stim and Orai as found in nonexcitable cells. The contribution of the elemental Ca signals from the SR, sparks and puffs, to global Ca signals, i.e., Ca waves and oscillations, is becoming clearer but is far from established. The dynamics of SR Ca release and uptake mechanisms are reviewed along with the control of luminal Ca. We review the growing list of the SR's functions that still includes Ca storage, contraction, and relaxation but has been expanded to encompass Ca homeostasis, generating local and global Ca signals, and contributing to cellular microdomains and signaling in other organelles, including mitochondria, lysosomes, and the nucleus. For an integrated approach, a review of aspects of the SR in health and disease and during development and aging are also included. While the sheer versatility of smooth muscle makes it foolish to have a "one model fits all" approach to this subject, we have tried to synthesize conclusions wherever possible.
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Affiliation(s)
- Susan Wray
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Liverpool, Merseyside L69 3BX, United Kingdom.
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15
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Cong B, Han G, Huang XH, Liu SH, Liu CL, Lin XZ, He PQ, Gasaino H. Molecular cloning and tissue expression patterns of a small conductance calcium-activated potassium channel gene in turbot (Scophthalmus maximus L.). FISH & SHELLFISH IMMUNOLOGY 2009; 27:221-229. [PMID: 19481607 DOI: 10.1016/j.fsi.2009.05.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Revised: 05/05/2009] [Accepted: 05/06/2009] [Indexed: 05/27/2023]
Abstract
Calcium-activated potassium channels on plasma membrane enable potassium influx into the cell with ensuing changes in plasma membrane potential and consequent effects on cellular metabolic functions. Recently, this potassium channel was reported to regulate the cellular responses of mammalian immune cells. We have postulated the presence of such a channel in fish immune cells and its potential role in immunoregulation in fish. Employing specific primers and RNA template, we cloned a segment of a novel gene from turbot blood sample and subsequently obtained a full cDNA sequence using RACE approaches. Bioinformatic analysis revealed structural and phylogenetic characteristics of a novel small conductance calcium-activated potassium channel gene, we called TSKCa, which exhibits homologous domains to other species particularly in the transmembrane regions. Full-length TSKCa cDNA is 1698 bp with a 1632 bp open reading frame encoding a protein of 544 amino acids. TSKCa gene is expressed in majority of the tested organs and tissues of turbot. To assess the postulated immune function of TSKCa, we infected turbot with the pathogen Vibrio anguillarum. Here, semi-quantitative RT-PCR analysis demonstrated increased mRNA expression of TSKCa in head kidney, spleen and blood, indicating an important role of TSKCa in these organ tissues that mediate the immune defense response of turbot. In contrast, there was less change in expression in the turbot intestines and liver which were less implicated in the immune response in present study.
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Affiliation(s)
- Bailin Cong
- The Key Laboratory of Marine Bioactive Substance, SOA, Qingdao 266061, PR China
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16
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Qu YJ, Bondarenko VE, Xie C, Wang S, Awayda MS, Strauss HC, Morales MJ. W-7 modulates Kv4.3: pore block and Ca2+-calmodulin inhibition. Am J Physiol Heart Circ Physiol 2007; 292:H2364-77. [PMID: 17220193 DOI: 10.1152/ajpheart.00409.2005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ca(+)-calmodulin (Ca(2+)-CaM)-dependent protein kinase II (Ca(2+)/CaMKII) is an important regulator of cardiac ion channels, and its inhibition may be an approach for treatment of ventricular arrhythmias. Using the two-electrode voltage-clamp technique, we investigated the role of W-7, an inhibitor of Ca(2+)-occupied CaM, and KN-93, an inhibitor of Ca(2+)/CaMKII, on the K(v)4.3 channel in Xenopus laevis oocytes. W-7 caused a voltage- and concentration-dependent decrease in peak current, with IC(50) of 92.4 muM. The block was voltage dependent, with an effective electrical distance of 0.18 +/- 0.05, and use dependence was observed, suggesting that a component of W-7 inhibition of K(v)4.3 current was due to open-channel block. W-7 made recovery from open-state inactivation a biexponential process, also suggesting open-channel block. We compared the effects of W-7 with those of KN-93 after washout of 500 muM BAPTA-AM. KN-93 reduced peak current without evidence of voltage or use dependence. Both W-7 and KN-93 accelerated all components of inactivation. We used wild-type and mutated K(v)4.3 channels with mutant CaMKII consensus phosphorylation sites to examine the effects of W-7 and KN-93. In contrast to W-7, KN-93 at 35 muM selectively accelerated open-state inactivation in the wild-type vs. the mutant channel. W-7 had a significantly greater effect on recovery from inactivation in wild-type than in mutant channels. We conclude that, at certain concentrations, KN-93 selectively inhibits Ca(2+)/CaMKII activity in Xenopus oocytes and that the effects of W-7 are mediated by direct interaction with the channel pore and inhibition of Ca(2+)-CaM, as well as a change in activity of Ca(2+)-CaM-dependent enzymes, including Ca(2+)/CaMKII.
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Affiliation(s)
- Yu-Jie Qu
- Department of Physiology and Biophysics, School of Medicine and Biomedical Sciences, University at Buffalo-State University of New York, 3435 Main Street, Buffalo, NY 14214, USA
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17
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Kim M, Han IS, Koh SD, Perrino BA. Roles of CaM kinase II and phospholamban in SNP-induced relaxation of murine gastric fundus smooth muscles. Am J Physiol Cell Physiol 2006; 291:C337-47. [PMID: 16510846 DOI: 10.1152/ajpcell.00397.2005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The mechanisms by which nitric oxide (NO) relaxes smooth muscles are unclear. The NO donor sodium nitroprusside (SNP) has been reported to increase the Ca2+ release frequency (Ca2+ sparks) through ryanodine receptors (RyRs) and activate spontaneous transient outward currents (STOCs), resulting in smooth muscle relaxation. Our findings that caffeine relaxes and hyperpolarizes murine gastric fundus smooth muscles and increases phospholamban (PLB) phosphorylation by Ca2+/calmodulin (CaM)-dependent protein kinase II (CaM kinase II) suggest that PLB phosphorylation by CaM kinase II participates in smooth muscle relaxation by increasing sarcoplasmic reticulum (SR) Ca2+ uptake and the frequencies of SR Ca2+ release events and STOCs. Thus, in the present study, we investigated the roles of CaM kinase II and PLB in SNP-induced relaxation of murine gastric fundus smooth muscles. SNP hyperpolarized and relaxed gastric fundus circular smooth muscles and activated CaM kinase II. SNP-induced CaM kinase II activation was prevented by KN-93. Ryanodine, tetracaine, 2-aminoethoxydiphenylborate, and cyclopiazonic acid inhibited SNP-induced fundus smooth muscle relaxation and CaM kinase II activation. The Ca2+-activated K+ channel blockers iberiotoxin and apamin inhibited SNP-induced hyperpolarization and relaxation. The soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4,3-alpha]quinoxalin-1-one inhibited SNP-induced relaxation and CaM kinase II activation. The membrane-permeable cGMP analog 8-bromo-cGMP relaxed gastric fundus smooth muscles and activated CaM kinase II. SNP increased phosphorylation of PLB at Ser16 and Thr17. Thr17 phosphorylation of PLB was inhibited by cyclopiazonic acid and KN-93. Ser16 and Thr17 phosphorylation of PLB was sensitive to 1H-[1,2,4]oxadiazolo-[4,3-alpha]quinoxalin-1-one. These results demonstrate a novel pathway linking the NO-soluble guanylyl cyclase-cGMP pathway, SR Ca2+ release, PLB, and CaM kinase II to relaxation in gastric fundus smooth muscles.
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Affiliation(s)
- Minkyung Kim
- Dept. of Physiology and Cell Biology, Univ. of Nevada School of Medicine, Anderson Bldg./MS352, Reno, NV 89557, USA
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18
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Sergeant GP, Ohya S, Reihill JA, Perrino BA, Amberg GC, Imaizumi Y, Horowitz B, Sanders KM, Koh SD. Regulation of Kv4.3 currents by Ca2+/calmodulin-dependent protein kinase II. Am J Physiol Cell Physiol 2005; 288:C304-13. [PMID: 15456698 DOI: 10.1152/ajpcell.00293.2004] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The voltage-dependent K+channel 4.3 (Kv4.3) is one of the major molecular correlates encoding a class of rapidly inactivating K+currents, including the transient outward current in the heart ( Ito) and A currents ( IA) in neuronal and smooth muscle preparations. Recent studies have shown that Itoin human atrial myocytes and IAin murine colonic myocytes are modulated by Ca2+/calmodulin-dependent protein kinase II (CaMKII); however, the molecular target of CaMKII in these studies has not been elucidated. We performed experiments to investigate whether CaMKII could regulate Kv4.3 currents directly. Inclusion of the autothiophosphorylated form of CaMKII in the patch pipette (10 nM) prolonged Kv4.3 currents such that the time required to reach 50% inactivation from peak more than doubled, with positive shifts in voltage dependence of both activation and inactivation. In contrast, the rate of recovery from inactivation was accelerated under these conditions. CaMKII-inhibitory peptide or KN-93 produced effects opposite to that above; thus the rate of inactivation was increased, and recovery from inactivation decreased. A number of mutagenesis experiments were conducted on the three candidate CaMKII consensus sequence sites on the channel. Mutations at S550A, located at the COOH-terminal region of the channel, resulted in currents that inactivated more rapidly but recovered from inactivation at a slower rate than that of wild-type controls. In addition, these currents were unaffected by dialysis with either autothiophosphorylated CaMKII or the specific inhibitory peptide of CaMKII, suggesting that CaMKII slows the inactivation and accelerates the rate of recovery from inactivation of Kv4.3 currents by a direct effect at S550A, located at the COOH-terminal region of the channel.
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Affiliation(s)
- Gerard P Sergeant
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA
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19
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Kramár EA, Lin B, Lin CY, Arai AC, Gall CM, Lynch G. A novel mechanism for the facilitation of theta-induced long-term potentiation by brain-derived neurotrophic factor. J Neurosci 2004; 24:5151-61. [PMID: 15175384 PMCID: PMC6729196 DOI: 10.1523/jneurosci.0800-04.2004] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) contributes to the induction of long-term potentiation (LTP) by theta-pattern stimulation, but the specific processes underlying this effect are not known. Experiments described here, using BDNF concentrations that have minor effects on baseline responses, show that the neurotrophin both reduces the threshold for LTP induction and elevates the ceiling on maximal potentiation. The enhanced LTP proved to be as stable and resistant to reversal as that recorded under control conditions. BDNF markedly increased the facilitation of burst responses that occurs within a theta train. This suggests that the neurotrophin acts on long-lasting events that (1) are set in motion by the first burst in a train and (2) regulate the amplitude of subsequent bursts. Whole-cell recordings established that BDNF causes a rapid reduction in the size of the long-lasting afterhyperpolarization (AHP) that follows individual theta bursts. Apamin, an antagonist of type 2 small-conductance Ca2+-activated potassium (SK2) channels, also reduced hippocampal AHPs and closely reproduced the effects of BDNF on theta-burst responses and LTP. The latter results were replicated with a newly introduced, highly selective inhibitor of SK2 channels. Immunoblot analyses indicated that BDNF increases SK2 serine phosphorylation in hippocampal slices. These findings point to the conclusion that BDNF-driven protein kinase cascades serve to depress the SK2 component, and possibly other constituents, of the AHP. It is likely that this mechanism, acting with other factors, promotes the formation and increases the magnitude of LTP.
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Affiliation(s)
- Enikö A Kramár
- Department of Psychiatry and Human Behavior, University of California, Irvine, California 92612-1695, USA.
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20
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Yang D, Thalmann I, Thalmann R, Simmons DD. Expression of alpha and beta parvalbumin is differentially regulated in the rat organ of corti during development. ACTA ACUST UNITED AC 2004; 58:479-92. [PMID: 14978725 DOI: 10.1002/neu.10289] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The expression of two calcium-binding proteins of the parvalbumin (PV) family, the alpha isoform (alphaPV) and the beta isoform known as oncomodulin (OM), was investigated in the rat cochlea during postnatal development and related to cholinergic efferent innervation. Using RT-PCR analysis, we found that OM expression begins between postnatal day 2 (P2) and P4, and peaks as early as P10, while alphaPV mRNA begins expression before birth and remains highly expressed into the adult period. Both in situ hybridization and immunoreactivity confirm that OM is uniquely expressed by the outer hair cells (OHCs) in the rat cochlea and occurs after efferent innervation along the cochlear spiral between P2 and P4. In contrast to OM expression, alphaPV immunoreactivity is expressed in both inner hair cells (IHCs) and OHCs at birth. Following olivocochlear efferent innervation, OHCs demonstrate weak OM immunoreactivity beginning at P5 and diminished alphaPV immunoreactivity after P10. In organ cultures isolated prior to the efferent innervation of OHCs, OM immunoreactivity failed to develop in OHCs, but alphaPV immunoreactivity remained present in both IHCs and OHCs. In contrast, organ cultures isolated after efferent innervation of OHCs show OHCs with low levels of OM immunoreactivity and high levels of alphaPV immunoreactivity. This study suggests that OM and alphaPV are differentially regulated in OHCs during cochlear development. Our findings further raise the possibility that the expression of PV proteins in OHCs may be influenced by efferent innervation.
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Affiliation(s)
- D Yang
- Siebens Hearing Research Center, Central Institute for the Deaf, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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21
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Ohya S, Horowitz B. Differential transcriptional expression of Ca2+ BP superfamilies in murine gastrointestinal smooth muscles. Am J Physiol Gastrointest Liver Physiol 2002; 283:G1290-7. [PMID: 12388203 DOI: 10.1152/ajpgi.00101.2002] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Calmodulin (Cal) plays important roles for contractile activity in smooth muscles. Recently, two distinct Ca(2+)-binding protein superfamilies with sequence similarities to Cal have been identified in neuronal cells: neuronal Ca(2+)-binding proteins (NCBPs) and Cal-like Ca(2+)-binding proteins (CaBPs). Some NCBPs and CaBPs play significant roles for Ca(2+)-dependent cellular signaling in the nervous system. In gastrointestinal smooth muscles (GISMs), Cal functions as the regulator of contractile behavior and electrical rhythmicity. However, the molecular identification of NCBPs and CaBPs has not been elucidated in GISMs. Here, we have identified NCBPs and CaBPs expressed in GISMs and determined the expression levels of their transcripts by quantitative RT-PCR. Of 12 NCBPs, the transcripts for neuronal Ca(2+) sensor 1, neural visinin-like proteins 1, 2, and 3, and K(+) channel-interacting proteins 1 and 3 were detected in proximal colon, gastric fundus, gastric antrum, and jejunum. On the other hand, of seven CaBPs including alternatively spliced variants, only CaBP1L transcripts were detected in GISMs.
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Affiliation(s)
- Susumu Ohya
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557-0046, USA
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22
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Lorenz JM, Riddervold MH, Beckett EAH, Baker SA, Perrino BA. Differential autophosphorylation of CaM kinase II from phasic and tonic smooth muscle tissues. Am J Physiol Cell Physiol 2002; 283:C1399-413. [PMID: 12372801 DOI: 10.1152/ajpcell.00020.2002] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ca+/calmodulin-dependent protein kinase II (CaM kinase II) is regulated by calcium oscillations, autophosphorylation, and its subunit composition. All four subunit isoforms were detected in gastric fundus and proximal colon smooth muscles by RT-PCR, but only the gamma and delta isoforms are expressed in myocytes. Relative gamma and delta message levels were quantitated by real-time PCR. CaM kinase II protein and Ca2+/calmodulin-stimulated (total) activity levels are higher in proximal colon smooth muscle lysates than in fundus lysates, but Ca2+/calmodulin-independent (autonomous) activity is higher in fundus lysates. CaM kinase II in fundus lysates is relatively unresponsive to Ca2+/calmodulin. Alkaline phosphatase decreased CaM kinase II autonomous activity in fundus lysates and restored its responsiveness to Ca2+/calmodulin. Acetylcholine (ACh) increased autonomous CaM kinase II activity in fundus and proximal colon smooth muscles in a time- and dose-dependent manner. KN-93 enhanced ACh-induced fundus contractions but inhibited proximal colon contractions. The different properties of CaM kinase II from fundus and proximal colon smooth muscles suggest differential regulation of its autophosphorylation and activity in tonic and phasic gastrointestinal smooth muscles.
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Affiliation(s)
- Jillinda M Lorenz
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA
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23
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Hennig GW, Smith CB, O'Shea DM, Smith TK. Patterns of intracellular and intercellular Ca2+ waves in the longitudinal muscle layer of the murine large intestine in vitro. J Physiol 2002; 543:233-53. [PMID: 12181295 PMCID: PMC2290473 DOI: 10.1113/jphysiol.2002.018986] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Ca2+ wave activity was monitored in the longitudinal (LM) layer of isolated murine caecum and proximal colon at 35 degrees C with fluo-4 AM and an iCCD camera. Both intracellular (within LM cells) and intercellular (also spreading from cell to cell) Ca2+ waves were observed. Intracellular Ca2+ waves were associated with a lack of muscle movement whereas intercellular Ca2+ waves, which were five times more intense than intracellular waves, were often associated with localized contractions. Several intracellular Ca2+ waves were present at the same time in individual LM cells. Waves in adjacent LM cells were not coordinated and were unaffected by TTX (1 microM) but were blocked by IP3 receptor antagonists xestospongin-C (Xe-C; 2 microM) or 2-aminoethyl diphenylborate (2-APB; 25 microM), and by ryanodine (10 microM). Caffeine (5 mM) restored wave activity following blockade with Xe-C. NiCl2 (1 mM) blocked intracellular Ca2+ waves, and nicardipine (2 microM) reduced their frequency and intensity, but did not affect their velocity, suggesting the sarcoplasmic reticulum may be fuelled by extracellular Ca2+ entry. Intercellular Ca2+ waves often occurred in bursts and propagated rapidly across sizeable regions of the LM layer and were blocked by heptanol (0.5 mM). Intercellular Ca2+ waves were dependent upon neural activity, external Ca2+ entry through L-type Ca2+ channels, and amplification via calcium-induced calcium release (CICR). In conclusion, intracellular Ca2+ waves, which may reduce muscle excitability, are confined to individual LM cells. They depend upon Ca2+ release from internal Ca2+ stores and are likely to be fuelled by extracellular Ca2+ entry. Intercellular Ca2+ waves, which are likely to underlie smooth muscle tone, mixing and propulsion, depend upon neural activity, muscle action potential propagation and amplification by CICR.
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Affiliation(s)
- Grant W Hennig
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
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24
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Park D, Coleman MJ, Hodge JJL, Budnik V, Griffith LC. Regulation of neuronal excitability in Drosophila by constitutively active CaMKII. JOURNAL OF NEUROBIOLOGY 2002; 52:24-42. [PMID: 12115891 DOI: 10.1002/neu.10066] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The ability of calcium/calmodulin-dependent protein kinase II (CaMKII) to become calcium independent after autophosphorylation makes this enzyme a temporal marker of neuronal activity. Here we show that the calcium-independent form of CaMKII has unique effects on larval viability, locomotion, and neuronal excitability in Drosophila. Expression of constitutively active T287D, but not calcium-dependent T287A, mutant CaMKII in Drosophila neurons resulted in decreased viability, behavioral defects, and failure of action potential propagation. The actions of T287D may be mediated, at least in part, by increased potassium conductances. Expression of T287D CaMKII also stimulated an increase in the number of boutons at the larval neuromuscular junction, but did not affect the mechanics of release. This study defines a role for autophosphorylation of CaMKII in the regulation of multiple neuronal functions including the intrinsic properties of neurons.
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Affiliation(s)
- Demian Park
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02254-9110, USA
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25
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Panofen F, Piwowarski T, Jeserich G. Small conductance calcium-activated potassium channels of trout CNS: molecular structure, developmental expression, and partial biophysical characterization. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2002; 101:1-11. [PMID: 12007826 DOI: 10.1016/s0169-328x(02)00131-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two small conductance calcium-activated potassium channels that exhibited amino acid similarity with mammalian SK2 and SK3, respectively, were PCR cloned from the CNS of trout and sequenced. Upon heterologous expression in Sf21 insect cells trout SK2 (termed tSK2) produced a calcium-dependent, voltage-insensitive, and non-inactivating current with a single unit conductance of about 11 pS. This current was half maximally activated by 0.76 microM Ca(2+) and blocked by picomolar concentrations of apamin but not by TEA. Transcripts of both SK-related channels possessed a widespread distribution in the mature brain tissue of trout and outside the nervous system were detectable in muscle tissue as well as in liver. As revealed by RT-PCR analysis transcripts encoding tSK2 and tSK3 channels were early detectable during brain development (stage 30, shortly after hatching).
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Affiliation(s)
- F Panofen
- Department of Animal Physiology, University of Osnabrück, Barbarastr. 11, 49069 Osnabrück, Germany
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26
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Bayguinov O, Hagen B, Kenyon JL, Sanders KM. Coupling strength between localized Ca(2+) transients and K(+) channels is regulated by protein kinase C. Am J Physiol Cell Physiol 2001; 281:C1512-23. [PMID: 11600414 DOI: 10.1152/ajpcell.2001.281.5.c1512] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Localized Ca(2+) transients resulting from inositol trisphosphate (IP(3))-dependent Ca(2+) release couple to spontaneous transient outward currents (STOCs) in murine colonic myocytes. Confocal microscopy and whole cell patch-clamp techniques were used to investigate coupling between localized Ca(2+) transients and STOCs. Colonic myocytes were loaded with fluo 3. Reduction in external Ca(2+) ([Ca(2+)](o)) reduced localized Ca(2+) transients but increased STOC amplitude and frequency. Simultaneous recordings of Ca(2+) transients and STOCs showed increased coupling strength between Ca(2+) transients and STOCs when [Ca(2+)](o) was reduced. Gd(3+) (10 microM) did not affect Ca(2+) transients but increased STOC amplitude and frequency. Similarly, an inhibitor of Ca(2+) influx, 1-2-(4-methoxyphenyl)-2-[3-(4-methoxyphenyl)propoxy]ethyl-1H-imidazole (SKF-96365), increased STOC amplitude and frequency. A protein kinase C (PKC) inhibitor, GF-109203X, also increased the amplitude and frequency of STOCs but had no effect on Ca(2+) transients. Phorbol 12-myristate 13-acetate (1 microM) reduced STOC amplitude and frequency but did not affect Ca(2+) transients. 4alpha-Phorbol (1 microM) had no effect on STOCs or Ca(2+) transients. Single channel studies indicated that large-conductance Ca(2+)-activated K(+) (BK) channels were inhibited by a Ca(2+)-dependent PKC. In summary 1) Ca(2+) release from IP(3) receptor-operated stores activates Ca(2+)-activated K(+) channels; 2) Ca(2+) influx through nonselective cation channels facilitates activation of PKC; and 3) PKC reduces the Ca(2+) sensitivity of BK channels, reducing the coupling strength between localized Ca(2+) transients and BK channels.
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Affiliation(s)
- O Bayguinov
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557-0046, USA
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27
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Zhang J, Li N, Yu J, Zhang W, Cao X. Molecular cloning and characterization of a novel calcium/calmodulin-dependent protein kinase II inhibitor from human dendritic cells. Biochem Biophys Res Commun 2001; 285:229-34. [PMID: 11444830 DOI: 10.1006/bbrc.2001.5175] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) is a widely distributed protein kinase that regulates numerous physiological functions. Inhibitors of CaMKII are useful tools for investigating the CaMKII functions. Here we identified a novel CaMKII inhibitor protein (CaM-KIIN) from the human dendritic cell cDNA library by large-scale random sequencing. Human CaM-KIIN contains 79 amino acids, which shares 98% identity and 98% positives with rat CaMKII inhibitor protein beta and 65% identity and 78% positives with rat CaMKII inhibitor alpha. Human CaM-KIIN mRNA expression was detectable in various tissues and cell lines by Northern blot and RT-PCR. To investigate its biological functions, full-length human CaM-KIIN was overexpressed in colon adenocarcinoma LoVo cells. When expressed in LoVo cells, it could inhibit cell proliferation, block cell growth, and decrease the viable cell number. These results characterize a potential cellular inhibitor protein of CaMKII that plays an important role in the regulation of cell growth.
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Affiliation(s)
- J Zhang
- Department of Clinical Laboratory, Changzheng Hospital, Shanghai 200003, People's Republic of China
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Gordienko DV, Greenwood IA, Bolton TB. Direct visualization of sarcoplasmic reticulum regions discharging Ca(2+)sparks in vascular myocytes. Cell Calcium 2001; 29:13-28. [PMID: 11133352 DOI: 10.1054/ceca.2000.0180] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Localized Ca(2+)-release events, Ca(2+)sparks, have been suggested to be the 'elementary building blocks' of the calcium signalling system in all types of muscles. In striated muscles these occur at regular intervals along the fibre corresponding to the sarcomeric structures which do not exist in smooth muscle. We showed previously that in visceral and vascular myocytes Ca(2+)sparks occurred much more frequently at certain sites (frequent discharge sites [FDSs]). In this paper, we have related the position of FDSs to the distribution of the sarcoplasmic reticulum in the same living myocyte. The three-dimensional distribution of the SR in freshly isolated rabbit portal vein myocytes was visualized by means of high-resolution confocal imaging after staining with DiOC(6)and/or BODIPY TR-X ryanodine. Both fluorochromes revealed a similar staining pattern indicating a helical arrangement of well-developed superficial SR which occupied about 6% of the cell volume. Computing the frequency of spontaneous Ca(2+)sparks detected by means of fluo-4 fluorescence revealed that in about 70% of myocytes there was only one major FDS located on a prominent portion of superficial SR network usually within 1-2 microm of the nuclear envelope, although a few sparks occurred at other sites scattered generally in superficial locations throughout the cell. Polarized mitochondria were readily identified by accumulation of tetramethylrhodamine ethyl ester (TMRE). These were closely associated with the SR network in extra-nuclear regions. TMRE staining, however, failed to reveal any mitochondria near the FDS-related SR element. When observed, propagating [Ca(2+)](i)waves and associated myocyte contractions were initiated at FDSs. This study provide first insight into the three-dimensional arrangement of the SR in living smooth muscle cells and relates the peculiarity of the structural organization of the myocyte to the features of Ca(2+)signalling at subcellular level.
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Affiliation(s)
- D V Gordienko
- Department of Pharmacology and Clinical Pharmacology, St. George's Hospital Medical School, Cranmer Terrace, London, UK.
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