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Salazar-Enciso R, Guerrero-Hernández A, Gómez AM, Benitah JP, Rueda A. Aldosterone-Induced Sarco/Endoplasmic Reticulum Ca2+ Pump Upregulation Counterbalances Cav1.2-Mediated Ca2+ Influx in Mesenteric Arteries. Front Physiol 2022; 13:834220. [PMID: 35360237 PMCID: PMC8963271 DOI: 10.3389/fphys.2022.834220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 02/08/2022] [Indexed: 11/26/2022] Open
Abstract
In mesenteric arteries (MAs), aldosterone (ALDO) binds to the endogenous mineralocorticoid receptor (MR) and increases the expression of the voltage-gated L-type Cav1.2 channel, an essential ion channel for vascular contraction, sarcoplasmic reticulum (SR) Ca2+ store refilling, and Ca2+ spark generation. In mesenteric artery smooth muscle cells (MASMCs), Ca2+ influx through Cav1.2 is the indirect mechanism for triggering Ca2+ sparks. This process is facilitated by plasma membrane-sarcoplasmic reticulum (PM-SR) nanojunctions that drive Ca2+ from the extracellular space into the SR via Sarco/Endoplasmic Reticulum Ca2+ (SERCA) pump. Ca2+ sparks produced by clusters of Ryanodine receptors (RyRs) at PM-SR nanodomains, decrease contractility by activating large-conductance Ca2+-activated K+ channels (BKCa channels), which generate spontaneous transient outward currents (STOCs). Altogether, Cav1.2, SERCA pump, RyRs, and BKCa channels work as a functional unit at the PM-SR nanodomain, regulating intracellular Ca2+ and vascular function. However, the effect of the ALDO/MR signaling pathway on this functional unit has not been completely explored. Our results show that short-term exposure to ALDO (10 nM, 24 h) increased the expression of Cav1.2 in rat MAs. The depolarization-induced Ca2+ entry increased SR Ca2+ load, and the frequencies of both Ca2+ sparks and STOCs, while [Ca2+]cyt and vasoconstriction remained unaltered in Aldo-treated MAs. ALDO treatment significantly increased the mRNA and protein expression levels of the SERCA pump, which counterbalanced the augmented Cav1.2-mediated Ca2+ influx at the PM-SR nanodomain, increasing SR Ca2+ content, Ca2+ spark and STOC frequencies, and opposing to hyperpolarization-induced vasoconstriction while enhancing Acetylcholine-mediated vasorelaxation. This work provides novel evidence for short-term ALDO-induced upregulation of the functional unit comprising Cav1.2, SERCA2 pump, RyRs, and BKCa channels; in which the SERCA pump buffers ALDO-induced upregulation of Ca2+ entry at the superficial SR-PM nanodomain of MASMCs, preventing ALDO-triggered depolarization-induced vasoconstriction and enhancing vasodilation. Pathological conditions that lead to SERCA pump downregulation, for instance, chronic exposure to ALDO, might favor the development of ALDO/MR-mediated augmented vasoconstriction of mesenteric arteries.
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Affiliation(s)
- Rogelio Salazar-Enciso
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, Mexico
- Signaling and Cardiovascular Pathophysiology - UMR-S 1180, Inserm, Université Paris-Saclay, Châtenay-Malabry, France
| | - Agustín Guerrero-Hernández
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, Mexico
| | - Ana M. Gómez
- Signaling and Cardiovascular Pathophysiology - UMR-S 1180, Inserm, Université Paris-Saclay, Châtenay-Malabry, France
| | - Jean-Pierre Benitah
- Signaling and Cardiovascular Pathophysiology - UMR-S 1180, Inserm, Université Paris-Saclay, Châtenay-Malabry, France
| | - Angélica Rueda
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, Mexico
- *Correspondence: Angélica Rueda,
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Chen X, Weber C, Farrell ET, Alvarado FJ, Zhao YT, Gómez AM, Valdivia HH. Sorcin ablation plus β-adrenergic stimulation generate an arrhythmogenic substrate in mouse ventricular myocytes. J Mol Cell Cardiol 2017; 114:199-210. [PMID: 29174767 DOI: 10.1016/j.yjmcc.2017.11.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 10/23/2017] [Accepted: 11/21/2017] [Indexed: 10/18/2022]
Abstract
Sorcin, a penta-EF hand Ca2+-binding protein expressed in cardiomyocytes, is known to interact with ryanodine receptors and other Ca2+ regulatory proteins. To investigate sorcin's influence on cardiac excitation-contraction coupling and its role in the development of cardiac malfunctions, we generated a sorcin knockout (KO) mouse model. Sorcin KO mice presented ventricular arrhythmia and sudden death when challenged by acute stress induced by isoproterenol plus caffeine. Chronic stress, which was induced by transverse aortic constriction, significantly decreased the survival rate of sorcin KO mice. Under isoproterenol stimulation, spontaneous Ca2+ release events were frequently observed in sorcin KO cardiomyocytes. Sorcin KO hearts of adult, but not young mice developed overexpression of L-type Ca2+ channel and Na+-Ca2+ exchanger, which enhanced ICa and INCX. Consequently, spontaneous Ca2+ release events in sorcin KO cardiomyocytes were more likely to induce arrhythmogenic delayed afterdepolarizations. Our study demonstrates sorcin deficiency may trigger cardiac ventricular arrhythmias due to Ca2+ disturbances, and evidences the critical role of sorcin in maintaining Ca2+ homeostasis, especially during the adrenergic response of the heart.
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Affiliation(s)
- Xi Chen
- Center for Arrhythmia Research, Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI 48109, USA; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Craig Weber
- Department of Physiology, University of Arizona College of Medicine, Tucson, AR 85724, USA
| | - Emily T Farrell
- Department of Pediatrics, Division of Cardiology, University of Wisconsin, Madison, WI 53705, USA
| | - Francisco J Alvarado
- Center for Arrhythmia Research, Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI 48109, USA; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Yan-Ting Zhao
- Center for Arrhythmia Research, Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI 48109, USA
| | - Ana M Gómez
- UMR-S 1180, Faculté de Pharmacie, Université Paris-Sud, Chatenay-Malabry 92296, France
| | - Héctor H Valdivia
- Center for Arrhythmia Research, Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI 48109, USA.
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Tykocki NR, Boerman EM, Jackson WF. Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles. Compr Physiol 2017; 7:485-581. [PMID: 28333380 DOI: 10.1002/cphy.c160011] [Citation(s) in RCA: 222] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.
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Affiliation(s)
- Nathan R Tykocki
- Department of Pharmacology, University of Vermont, Burlington, Vermont, USA
| | - Erika M Boerman
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, USA
| | - William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
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Rueda A, de Alba-Aguayo DR, Valdivia HH. [Ryanodine receptor, calcium leak and arrhythmias]. ARCHIVOS DE CARDIOLOGIA DE MEXICO 2014; 84:191-201. [PMID: 25103920 DOI: 10.1016/j.acmx.2013.12.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 10/30/2013] [Accepted: 12/02/2013] [Indexed: 11/28/2022] Open
Abstract
The participation of the ionic Ca(2+) release channel/ryanodine receptor in cardiac excitation-contraction coupling is well known since the late '80s, when various seminal papers communicated its purification for the first time and its identity with the "foot" structures located at the terminal cisternae of the sarcoplasmic reticulum. In addition to its main role as the Ca(2+) channel responsible for the transient Ca(2+) increase that activates the contractile machinery of the cardiomyocytes, the ryanodine receptor releases Ca(2+) during the relaxation phase of the cardiac cycle, giving rise to a diastolic Ca(2+) leak. In normal physiological conditions, diastolic Ca(2+) leak regulates the proper level of luminal Ca(2+), but in pathological conditions it participates in the generation of both, acquired and hereditary arrhythmias. Very recently, several groups have focused their efforts into the development of pharmacological tools to control the altered diastolic Ca(2+) leak via ryanodine receptors. In this review, we focus our interest on describing the participation of cardiac ryanodine receptor in the diastolic Ca(2+) leak under physiological or pathological conditions and also on the therapeutic approaches to control its undesired exacerbated activity during diastole.
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Affiliation(s)
- Angélica Rueda
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN, Unidad Zacatenco, México D.F., México.
| | - David R de Alba-Aguayo
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN, Unidad Zacatenco, México D.F., México
| | - Héctor H Valdivia
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI, Estados Unidos
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Goldstein JA, Bogdanovich S, Beiriger A, Wren LM, Rossi AE, Gao QQ, Gardner BB, Earley JU, Molkentin JD, McNally EM. Excess SMAD signaling contributes to heart and muscle dysfunction in muscular dystrophy. Hum Mol Genet 2014; 23:6722-31. [PMID: 25070948 DOI: 10.1093/hmg/ddu390] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Disruption of the dystrophin complex causes muscle injury, dysfunction, cell death and fibrosis. Excess transforming growth factor (TGF) β signaling has been described in human muscular dystrophy and animal models, where it is thought to relate to the progressive fibrosis that characterizes dystrophic muscle. We now found that canonical TGFβ signaling acutely increases when dystrophic muscle is stimulated to contract. Muscle lacking the dystrophin-associated protein γ-sarcoglycan (Sgcg null) was subjected to a lengthening protocol to produce maximal muscle injury, which produced rapid accumulation of nuclear phosphorylated SMAD2/3. To test whether reducing SMAD signaling improves muscular dystrophy in mice, we introduced a heterozygous mutation of SMAD4 (S4) into Sgcg mice to reduce but not ablate SMAD4. Sgcg/S4 mice had improved body mass compared with Sgcg mice, which normally show a wasting phenotype similar to human muscular dystrophy patients. Sgcg/S4 mice had improved cardiac function as well as improved twitch and tetanic force in skeletal muscle. Functional enhancement in Sgcg/S4 muscle occurred without a reduction in fibrosis, suggesting that intracellular SMAD4 targets may be important. An assessment of genes differentially expressed in Sgcg muscle focused on those encoding calcium-handling proteins and responsive to TGFβ since this pathway is a target for mediating improvement in muscular dystrophy. These data demonstrate that excessive TGFβ signaling alters cardiac and muscle performance through the intracellular SMAD pathway.
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Affiliation(s)
| | | | | | | | | | - Quan Q Gao
- Committee on Development, Regeneration, and Stem Cell Biology
| | | | | | - Jeffery D Molkentin
- Cincinnati Children's Hospital Medical Center, Department of Pediatrics, and Howard Hughes Medical Institutes, University of Cincinnati, Cincinnati, 240 Albert Sabin Way, Cincinnati, OH 45229, USA
| | - Elizabeth M McNally
- Department of Medicine Department of Human Genetics, The University of Chicago, Chicago, IL, USA and
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Rueda A, Fernández-Velasco M, Benitah JP, Gómez AM. Abnormal Ca2+ spark/STOC coupling in cerebral artery smooth muscle cells of obese type 2 diabetic mice. PLoS One 2013; 8:e53321. [PMID: 23301060 PMCID: PMC3536748 DOI: 10.1371/journal.pone.0053321] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Accepted: 11/30/2012] [Indexed: 01/19/2023] Open
Abstract
Diabetes is a major risk factor for stroke. However, the molecular mechanisms involved in cerebral artery dysfunction found in the diabetic patients are not completely elucidated. In cerebral artery smooth muscle cells (CASMCs), spontaneous and local increases of intracellular Ca2+ due to the opening of ryanodine receptors (Ca2+ sparks) activate large conductance Ca2+-activated K+ (BK) channels that generate spontaneous transient outward currents (STOCs). STOCs have a key participation in the control of vascular myogenic tone and blood pressure. Our goal was to investigate whether alterations in Ca(2+) spark and STOC activities, measured by confocal microscopy and patch-clamp technique, respectively, occur in isolated CASMCs of an experimental model of type-2 diabetes (db/db mouse). We found that mean Ca(2+) spark amplitude, duration, size and rate-of-rise were significantly smaller in Fluo-3 loaded db/db compared to control CASMCs, with a subsequent decrease in the total amount of Ca(2+) released through Ca(2+) sparks in db/db CASMCs, though Ca(2+) spark frequency remained. Interestingly, the frequency of large-amplitude Ca(2+) sparks was also significantly reduced in db/db cells. In addition, the frequency and amplitude of STOCs were markedly reduced at all voltages tested (from -50 to 0 mV) in db/db CASMCs. The latter correlates with decreased BK channel β1/α subunit ratio found in db/db vascular tissues. Taken together, Ca(2+) spark alterations lead to inappropriate BK channels activation in CASMCs of db/db mice and this condition is aggravated by the decrease in the BK β1 subunit/α subunit ratio which underlies the significant reduction of Ca(2+) spark/STOC coupling in CASMCs of diabetic animals.
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Affiliation(s)
- Angélica Rueda
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN, México City, México
- Inserm, U-637; Université de Montpellier 1, Université de Montpellier 2, Montpellier, France
- * E-mail: (AMG); (AR)
| | - María Fernández-Velasco
- Inserm, U-637; Université de Montpellier 1, Université de Montpellier 2, Montpellier, France
- Instituto de Investigación Hospital Universitario La Paz (IdiPAZ), Madrid, Spain
| | - Jean-Pierre Benitah
- Inserm, U769; Université de Paris-Sud, IFR141, Labex Lermit, Châtenay-Malabry, France
| | - Ana María Gómez
- Inserm, U769; Université de Paris-Sud, IFR141, Labex Lermit, Châtenay-Malabry, France
- * E-mail: (AMG); (AR)
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7
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Zhang J, Zhou J, Cai L, Lu Y, Wang T, Zhu L, Hu Q. Extracellular calcium-sensing receptor is critical in hypoxic pulmonary vasoconstriction. Antioxid Redox Signal 2012; 17:471-84. [PMID: 22098336 DOI: 10.1089/ars.2011.4168] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
AIMS The initiation of hypoxic pulmonary vasoconstriction (HPV) involves an increase in cytosolic calcium ([Ca(2+)](i)) in pulmonary artery (PA) smooth muscle cells (PASMCs). Both the processes depend on extracellular Ca(2+). Extracellular Ca(2+) can be sensed by extracellular calcium-sensing receptor (CaSR). This study aims at determining whether CaSR is pivotal in the initiation of HPV. RESULTS Experiments were performed in cultured PASMCs, isolated PAs, and rats including CaSR knockdown preparations. Both hypoxia and H(2)O(2) equivalent to the level achieved by hypoxia increased [Ca(2+)](i) in an extracellular Ca(2+)-dependent manner in PASMCs, and this was inhibited by CaSR knockdown or its negative allosteric modulator, Calhex231. Hypoxia-increased H(2)O(2) generation was diminished by mitochondria depletion. Mitochondria depletion abolished hypoxia-induced [Ca(2+)](i) increase (HICI), which was reversed by H(2)O(2) repletion. CaSR knockdown or Calhex231, however, prevented the reversible effect of H(2)O(2). HICI was abolished by catalase-polyethylene glycol (PEG-Catalase), not superoxide dismutase-polyethylene glycol (PEG-SOD) pretreatment, attenuated by ryanodine receptor3-knockdown or inhibition of store-operated Ca(2+) entry. HPV in vitro and in vivo was inhibited by Calhex231 and by CaSR knockdown. INNOVATION A novel mechanism underlying HPV is revealed by the role of CaSR in orchestrating reactive oxygen species and [Ca(2+)](i) signaling. CONCLUSIONS The activation of mitochondrial H(2)O(2)-sensitized CaSR by extracellular Ca(2+) mediates HICI in PASMCs and, thus, initiates HPV.
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Affiliation(s)
- Jiwei Zhang
- Department of Pathophysiology, Tongji Medical College, Huazhong University of Science and Technology (HUST), Wuhan, People's Republic of China
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Sorcin, a potential therapeutic target for reversing multidrug resistance in cancer. J Physiol Biochem 2012; 68:281-7. [DOI: 10.1007/s13105-011-0140-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Takeda Y, Nystoriak MA, Nieves-Cintrón M, Santana LF, Navedo MF. Relationship between Ca2+ sparklets and sarcoplasmic reticulum Ca2+ load and release in rat cerebral arterial smooth muscle. Am J Physiol Heart Circ Physiol 2011; 301:H2285-94. [PMID: 21984539 PMCID: PMC3233819 DOI: 10.1152/ajpheart.00488.2011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 09/30/2011] [Indexed: 11/22/2022]
Abstract
Ca(+) sparklets are subcellular Ca(2+) signals produced by the opening of sarcolemmal L-type Ca(2+) channels. Ca(2+) sparklet activity varies within the sarcolemma of arterial myocytes. In this study, we examined the relationship between Ca(2+) sparklet activity and sarcoplasmic reticulum (SR) Ca(2+) accumulation and release in cerebral arterial myocytes. Our data indicate that the SR is a vast organelle with multiple regions near the sarcolemma of these cells. Ca(2+) sparklet sites were located at or <0.2 μm from SR-sarcolemmal junctions. We found that while Ca(2+) sparklets increase the rate of SR Ca(2+) refilling in arterial myocytes, their activity did not induce regional variations in SR Ca(2+) content or Ca(2+) spark activity. In arterial myocytes, L-type Ca(2+) channel activity was independent of SR Ca(2+) load. This ruled out a potential feedback mechanism whereby SR Ca(2+) load regulates the activity of these channels. Together, our data suggest a model in which Ca(2+) sparklets contribute Ca(2+) influx into a cytosolic Ca(2+) pool from which sarco(endo)plasmic reticulum Ca(2+)-ATPase pumps Ca(2+) into the SR, indirectly regulating SR function.
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Affiliation(s)
- Yukari Takeda
- Department of Physiology and Biophysics, University of Washington, Seattle, 98195, USA
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Westcott EB, Jackson WF. Heterogeneous function of ryanodine receptors, but not IP3 receptors, in hamster cremaster muscle feed arteries and arterioles. Am J Physiol Heart Circ Physiol 2011; 300:H1616-30. [PMID: 21357503 DOI: 10.1152/ajpheart.00728.2010] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The roles played by ryanodine receptors (RyRs) and inositol 1,4,5-trisphosphate receptors (IP₃Rs) in vascular smooth muscle in the microcirculation remain unclear. Therefore, the function of both RyRs and IP₃Rs in Ca(²+) signals and myogenic tone in hamster cremaster muscle feed arteries and downstream arterioles were assessed using confocal imaging and pressure myography. Feed artery vascular smooth muscle displayed Ca(²+) sparks and Ca(²+) waves, which were inhibited by the RyR antagonists ryanodine (10 μM) or tetracaine (100 μM). Despite the inhibition of sparks and waves, ryanodine or tetracaine increased global intracellular Ca(²+) and constricted the arteries. The blockade of IP₃Rs with xestospongin D (5 μM) or 2-aminoethoxydiphenyl borate (100 μM) or the inhibition of phospholipase C using U-73122 (10 μM) also attenuated Ca(2+) waves without affecting Ca(²+) sparks. Importantly, the IP₃Rs and phospholipase C antagonists decreased global intracellular Ca(2+) and dilated the arteries. In contrast, cremaster arterioles displayed only Ca(²+) waves: Ca(²+) sparks were not observed, and neither ryanodine (10-50 μM) nor tetracaine (100 μM) affected either Ca(²+) signals or arteriolar tone despite the presence of functional RyRs as assessed by responses to the RyR agonist caffeine (10 mM). As in feed arteries, arteriolar Ca(²+) waves were attenuated by xestospongin D (5 μM), 2-aminoethoxydiphenyl borate (100 μM), and U-73122 (10 μM), accompanied by decreased global intracellular Ca(²+) and vasodilation. These findings highlight the contrasting roles played by RyRs and IP₃Rs in Ca(²+) signals and myogenic tone in feed arteries and demonstrate important differences in the function of RyRs between feed arteries and downstream arterioles.
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Affiliation(s)
- Erika B Westcott
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA.
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Activation of the cardiac Na(+)-Ca(2+) exchanger by sorcin via the interaction of the respective Ca(2+)-binding domains. J Mol Cell Cardiol 2010; 49:132-41. [PMID: 20298697 PMCID: PMC2958309 DOI: 10.1016/j.yjmcc.2010.03.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 01/21/2010] [Accepted: 03/08/2010] [Indexed: 11/24/2022]
Abstract
Sorcin is a penta-EF-hand protein that interacts with intracellular target proteins after Ca2+ binding. The sarcolemmal Na+/Ca2+ exchanger (NCX1) may be an important sorcin target in cardiac muscle. In this study, RNAi knockdown of sorcin, purified sorcin or sorcin variants was employed in parallel measurements of: (i) NCX activity in isolated rabbit cardiomyocytes using electrophysiological techniques and (ii) sorcin binding to the NCX1 calcium binding domains (CBD1 and (iii) using surface plasmon resonance and gel overlay techniques. Sorcin is activated by Ca2+ binding to the EF3 and EF2 regions, which are connected by the D helix. To investigate the importance of this region in the interaction with NCX1, three variants were examined: W105G and W99G, mutated respectively near EF3 and EF2, and E124A that does not bind Ca2+ due to a mutation at EF3. Downregulation of sorcin decreased and supplementation with wt sorcin (3 μM) increased NCX activity in isolated cardiomyocytes. The relative stimulatory effects of the sorcin variants were: W105G > wt sorcin > Sorcin Calcium Binding Domain (SCBD) > W99G > E124A. Sorcin binding to both CBD1 and 2 was observed. In the presence of 50 µM Ca2+, the interaction with CBD1 followed the order W105G > SCBD > wt sorcin > W99G > E124A. In sorcin, the interacting surface can be mapped on the C-terminal Ca2+-binding domain in the D helix region comprising W99. The fast association/dissociation rates that characterize the interaction of sorcin with CBD1 and 2 may permit complex formation/dissociation during an excitation/contraction cycle.
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Role of ryanodine receptor subtypes in initiation and formation of calcium sparks in arterial smooth muscle: comparison with striated muscle. J Biomed Biotechnol 2009; 2009:135249. [PMID: 20029633 PMCID: PMC2793424 DOI: 10.1155/2009/135249] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Accepted: 09/22/2009] [Indexed: 11/17/2022] Open
Abstract
Calcium sparks represent local, rapid, and transient calcium release events from a cluster of ryanodine receptors (RyRs) in the sarcoplasmic reticulum. In arterial smooth muscle cells (SMCs), calcium sparks activate calcium-dependent potassium channels causing decrease in the global intracellular [Ca2+] and oppose vasoconstriction. This is in contrast to cardiac and skeletal muscle, where spatial and temporal summation of calcium sparks leads to global increases in intracellular [Ca2+] and myocyte contraction. We summarize the present data on local RyR calcium signaling in arterial SMCs in comparison to striated muscle and muscle-specific differences in coupling between L-type calcium channels and RyRs. Accordingly, arterial SMC Ca(v)1.2 L-type channels regulate intracellular calcium stores content, which in turn modulates calcium efflux though RyRs. Downregulation of RyR2 up to a certain degree is compensated by increased SR calcium content to normalize calcium sparks. This indirect coupling between Ca(v)1.2 and RyR in arterial SMCs is opposite to striated muscle, where triggering of calcium sparks is controlled by rapid and direct cross-talk between Ca(v)1.1/Ca(v)1.2 L-type channels and RyRs. We discuss the role of RyR isoforms in initiation and formation of calcium sparks in SMCs and their possible molecular binding partners and regulators, which differ compared to striated muscle.
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Franceschini S, Ilari A, Verzili D, Zamparelli C, Antaramian A, Rueda A, Valdivia HH, Chiancone E, Colotti G. Molecular basis for the impaired function of the natural F112L sorcin mutant: X-ray crystal structure, calcium affinity, and interaction with annexin VII and the ryanodine receptor. FASEB J 2007; 22:295-306. [PMID: 17699613 DOI: 10.1096/fj.07-8988com] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The penta-EF hand protein sorcin participates in the modulation of Ca2+-induced calcium-release in the heart through the interaction with several Ca2+ channels such as the ryanodine receptor. The modulating activity is impaired in the recently described natural F112L mutant. The F112 residue is located at the end of the D helix next to Asp113, one of the calcium ligands in the EF3 hand endowed with the highest affinity for the metal. The F112L-sorcin X-ray crystal structure at 2.5 A resolution displays marked alterations in the EF3 hand, where the hydrogen bonding network established by Phe112 is disrupted, and in the EF1 region, which is tilted in both monomers that give rise to the dimer, the stable form of the molecule. In turn, the observed tilt is indicative of an increased flexibility of the N-terminal part of the molecule. The structural alterations result in a 6-fold decrease in calcium affinity with respect to the wild-type protein and to an even larger impairment of the interaction with annexin VII and of the ability of sorcin to interact with and inhibit ryanodine receptors. These results provide a plausible structural and functional framework that helps elucidate the phenotypic alterations of mice overexpressing F112L-sorcin.
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Affiliation(s)
- Stefano Franceschini
- CNR Institute of Molecular Biology and Pathology, University Sapienza, P.le A.Moro 5, 00185 Rome, Italy
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