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Raguimova ON, Aguayo-Ortiz R, Robia SL, Espinoza-Fonseca LM. Dynamics-Driven Allostery Underlies Ca 2+-Mediated Release of SERCA Inhibition by Phospholamban. Biophys J 2020; 119:1917-1926. [PMID: 33069270 PMCID: PMC7677127 DOI: 10.1016/j.bpj.2020.09.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 09/17/2020] [Accepted: 09/18/2020] [Indexed: 12/20/2022] Open
Abstract
Sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA) and phospholamban (PLB) are essential for intracellular Ca2+ transport in myocytes. Ca2+-dependent activation of SERCA-PLB provides a control function that regulates cytosolic and SR Ca2+ levels. Although experimental and computational studies alone have led to a greater insight into SERCA-PLB regulation, the structural mechanisms for Ca2+ binding reversing inhibition of the complex remain poorly understood. Therefore, we have performed atomistic simulations totaling 32.7 μs and cell-based intramolecular fluorescence resonance energy transfer (FRET) experiments to determine structural changes of PLB-bound SERCA in response to binding of a single Ca2+ ion. Complementary MD simulations and FRET experiments showed that open-to-closed transitions in the structure of the headpiece underlie PLB inhibition of SERCA, and binding of a single Ca2+ ion is sufficient to shift the protein population toward a structurally closed structure of the complex. Closure is accompanied by functional interactions between the N-domain β5-β6 loop and the A-domain and the displacement of the catalytic phosphorylation domain toward a competent structure. We propose that reversal of SERCA-PLB inhibition is achieved by stringing together its controlling modules (A-domain and loop Nβ5-β6) with catalytic elements (P-domain) to regulate function during intracellular Ca2+ signaling. We conclude that binding of a single Ca2+ is a critical mediator of allosteric signaling that dictates structural changes and motions that relieve SERCA inhibition by PLB. Understanding allosteric regulation is of paramount importance to guide therapeutic modulation of SERCA and other evolutionarily related ion-motive ATPases.
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Affiliation(s)
- Olga N Raguimova
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois
| | - Rodrigo Aguayo-Ortiz
- Center for Arrhythmia Research, Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan
| | - Seth L Robia
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois
| | - L Michel Espinoza-Fonseca
- Center for Arrhythmia Research, Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan.
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Makarewich CA, Munir AZ, Schiattarella GG, Bezprozvannaya S, Raguimova ON, Cho EE, Vidal AH, Robia SL, Bassel-Duby R, Olson EN. The DWORF micropeptide enhances contractility and prevents heart failure in a mouse model of dilated cardiomyopathy. eLife 2018; 7:e38319. [PMID: 30299255 PMCID: PMC6202051 DOI: 10.7554/elife.38319] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Accepted: 09/26/2018] [Indexed: 01/01/2023] Open
Abstract
Calcium (Ca2+) dysregulation is a hallmark of heart failure and is characterized by impaired Ca2+ sequestration into the sarcoplasmic reticulum (SR) by the SR-Ca2+-ATPase (SERCA). We recently discovered a micropeptide named DWORF (DWarf Open Reading Frame) that enhances SERCA activity by displacing phospholamban (PLN), a potent SERCA inhibitor. Here we show that DWORF has a higher apparent binding affinity for SERCA than PLN and that DWORF overexpression mitigates the contractile dysfunction associated with PLN overexpression, substantiating its role as a potent activator of SERCA. Additionally, using a well-characterized mouse model of dilated cardiomyopathy (DCM) due to genetic deletion of the muscle-specific LIM domain protein (MLP), we show that DWORF overexpression restores cardiac function and prevents the pathological remodeling and Ca2+ dysregulation classically exhibited by MLP knockout mice. Our results establish DWORF as a potent activator of SERCA within the heart and as an attractive candidate for a heart failure therapeutic.
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Affiliation(s)
- Catherine A Makarewich
- Department of Molecular Biology and Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Amir Z Munir
- Department of Molecular Biology and Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Gabriele G Schiattarella
- Department of Internal MedicineUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Svetlana Bezprozvannaya
- Department of Molecular Biology and Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Olga N Raguimova
- Department of Cell and Molecular PhysiologyLoyola University ChicagoMaywoodUnited States
| | - Ellen E Cho
- Department of Cell and Molecular PhysiologyLoyola University ChicagoMaywoodUnited States
| | - Alexander H Vidal
- Department of Molecular Biology and Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Seth L Robia
- Department of Cell and Molecular PhysiologyLoyola University ChicagoMaywoodUnited States
| | - Rhonda Bassel-Duby
- Department of Molecular Biology and Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasUnited States
| | - Eric N Olson
- Department of Molecular Biology and Hamon Center for Regenerative Science and MedicineUniversity of Texas Southwestern Medical CenterDallasUnited States
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Raguimova ON, Smolin N, Bovo E, Bhayani S, Autry JM, Zima AV, Robia SL. Redistribution of SERCA calcium pump conformers during intracellular calcium signaling. J Biol Chem 2018; 293:10843-10856. [PMID: 29764938 PMCID: PMC6052202 DOI: 10.1074/jbc.ra118.002472] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 05/01/2018] [Indexed: 11/06/2022] Open
Abstract
The conformational changes of a calcium transport ATPase were investigated with molecular dynamics (MD) simulations as well as fluorescence resonance energy transfer (FRET) measurements to determine the significance of a discrete structural element for regulation of the conformational dynamics of the transport cycle. Previous MD simulations indicated that a loop in the cytosolic domain of the SERCA calcium transporter facilitates an open-to-closed structural transition. To investigate the significance of this structural element, we performed additional MD simulations and new biophysical measurements of SERCA structure and function. Rationally designed in silico mutations of three acidic residues of the loop decreased SERCA domain-domain contacts and increased domain-domain separation distances. Principal component analysis of MD simulations suggested decreased sampling of compact conformations upon N-loop mutagenesis. Deficits in headpiece structural dynamics were also detected by measuring intramolecular FRET of a Cer-YFP-SERCA construct (2-color SERCA). Compared with WT, the mutated 2-color SERCA shows a partial FRET response to calcium, whereas retaining full responsiveness to the inhibitor thapsigargin. Functional measurements showed that the mutated transporter still hydrolyzes ATP and transports calcium, but that maximal enzyme activity is reduced while maintaining similar calcium affinity. In live cells, calcium elevations resulted in concomitant FRET changes as the population of WT 2-color SERCA molecules redistributed among intermediates of the transport cycle. Our results provide novel insights on how the population of SERCA pumps responds to dynamic changes in intracellular calcium.
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Affiliation(s)
- Olga N Raguimova
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153 and
| | - Nikolai Smolin
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153 and
| | - Elisa Bovo
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153 and
| | - Siddharth Bhayani
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153 and
| | - Joseph M Autry
- the Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455
| | - Aleksey V Zima
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153 and
| | - Seth L Robia
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153 and
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Moser BA, Raguimova ON, Nakamura TM. Ccq1-Tpz1TPP1 interaction facilitates telomerase and SHREC association with telomeres in fission yeast. Mol Biol Cell 2015; 26:3857-66. [PMID: 26354422 PMCID: PMC4626069 DOI: 10.1091/mbc.e15-07-0481] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 09/04/2015] [Indexed: 01/31/2023] Open
Abstract
Through characterization of ccq1 mutants that disrupt Ccq1-Tpz1TPP1 interaction, the authors establish that Ccq1-Tpz1TPP1 interaction contributes to optimal binding of the Ccq1-SHREC complex and is required for Ccq1 Thr93 phosphorylation and telomerase recruitment. Evolutionarily conserved shelterin complex is essential for telomere maintenance in the fission yeast Schizosaccharomyces pombe. Elimination of the fission yeast shelterin subunit Ccq1 causes progressive loss of telomeres due to the inability to recruit telomerase, activates the DNA damage checkpoint, and loses heterochromatin at telomere/subtelomere regions due to reduced recruitment of the heterochromatin regulator complex Snf2/histone deacetylase–containing repressor complex (SHREC). The shelterin subunit Tpz1TPP1 directly interacts with Ccq1 through conserved C-terminal residues in Tpz1TPP1, and tpz1 mutants that fail to interact with Ccq1 show telomere shortening, checkpoint activation, and loss of heterochromatin. While we have previously concluded that Ccq1-Tpz1TPP1 interaction contributes to Ccq1 accumulation and telomerase recruitment based on analysis of tpz1 mutants that fail to interact with Ccq1, another study reported that loss of Ccq1-Tpz1TPP1 interaction does not affect accumulation of Ccq1 or telomerase. Furthermore, it remained unclear whether loss of Ccq1-Tpz1TPP1 interaction affects SHREC accumulation at telomeres. To resolve these issues, we identified and characterized a series of ccq1 mutations that disrupt Ccq1-Tpz1TPP1 interaction. Characterization of these ccq1 mutants established that Ccq1-Tpz1TPP1 interaction contributes to optimal binding of the Ccq1-SHREC complex, and is critical for Rad3ATR/Tel1ATM-dependent Ccq1 Thr93 phosphorylation and telomerase recruitment.
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Affiliation(s)
- Bettina A Moser
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607
| | - Olga N Raguimova
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607
| | - Toru M Nakamura
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607
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Iram SH, Gruber SJ, Raguimova ON, Thomas DD, Robia SL. ATP-Binding Cassette Transporter Structure Changes Detected by Intramolecular Fluorescence Energy Transfer for High-Throughput Screening. Mol Pharmacol 2015; 88:84-94. [PMID: 25924616 DOI: 10.1124/mol.114.096792] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 04/29/2015] [Indexed: 11/22/2022] Open
Abstract
Multidrug resistance protein 1 (MRP1) actively transports a wide variety of drugs out of cells. To quantify MRP1 structural dynamics, we engineered a "two-color MRP1" construct by fusing green fluorescent protein (GFP) and TagRFP to MRP1 nucleotide-binding domains NBD1 and NBD2, respectively. The recombinant MRP1 protein expressed and trafficked normally to the plasma membrane. Two-color MRP1 transport activity was normal, as shown by vesicular transport of [(3)H]17β-estradiol-17-β-(D-glucuronide) and doxorubicin efflux in AAV-293 cells. We quantified fluorescence resonance energy transfer (FRET) from GFP to TagRFP as an index of NBD conformational changes. Our results show that ATP binding induces a large-amplitude conformational change that brings the NBDs into closer proximity. FRET was further increased by substrate in the presence of ATP but not by substrate alone. The data suggest that substrate binding is required to achieve a fully closed and compact structure. ATP analogs bind MRP1 with reduced apparent affinity, inducing a partially closed conformation. The results demonstrate the utility of the two-color MRP1 construct for investigating ATP-binding cassette transporter structural dynamics, and it holds great promise for high-throughput screening of chemical libraries for unknown activators, inhibitors, or transportable substrates of MRP1.
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Affiliation(s)
- Surtaj H Iram
- Department of Cell and Molecular Physiology (S.H.I., O.N.R., S.L.R.), Cardiovascular Research Institute (O.N.R., S.L.R.), Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois; and Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota (S.J.G., D.D.T); and Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota (S.H.I.)
| | - Simon J Gruber
- Department of Cell and Molecular Physiology (S.H.I., O.N.R., S.L.R.), Cardiovascular Research Institute (O.N.R., S.L.R.), Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois; and Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota (S.J.G., D.D.T); and Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota (S.H.I.)
| | - Olga N Raguimova
- Department of Cell and Molecular Physiology (S.H.I., O.N.R., S.L.R.), Cardiovascular Research Institute (O.N.R., S.L.R.), Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois; and Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota (S.J.G., D.D.T); and Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota (S.H.I.)
| | - David D Thomas
- Department of Cell and Molecular Physiology (S.H.I., O.N.R., S.L.R.), Cardiovascular Research Institute (O.N.R., S.L.R.), Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois; and Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota (S.J.G., D.D.T); and Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota (S.H.I.)
| | - Seth L Robia
- Department of Cell and Molecular Physiology (S.H.I., O.N.R., S.L.R.), Cardiovascular Research Institute (O.N.R., S.L.R.), Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois; and Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota (S.J.G., D.D.T); and Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota (S.H.I.)
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