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Sergienko NM, Donner DG, Delbridge LMD, McMullen JR, Weeks KL. Protein phosphatase 2A in the healthy and failing heart: New insights and therapeutic opportunities. Cell Signal 2021; 91:110213. [PMID: 34902541 DOI: 10.1016/j.cellsig.2021.110213] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 12/02/2021] [Accepted: 12/07/2021] [Indexed: 02/06/2023]
Abstract
Protein phosphatases have emerged as critical regulators of phosphoprotein homeostasis in settings of health and disease. Protein phosphatase 2A (PP2A) encompasses a large subfamily of enzymes that remove phosphate groups from serine/threonine residues within phosphoproteins. The heterogeneity in PP2A structure, which arises from the grouping of different catalytic, scaffolding and regulatory subunit isoforms, creates distinct populations of catalytically active enzymes (i.e. holoenzymes) that localise to different parts of the cell. This structural complexity, combined with other regulatory mechanisms, such as interaction of PP2A heterotrimers with accessory proteins and post-translational modification of the catalytic and/or regulatory subunits, enables PP2A holoenzymes to target phosphoprotein substrates in a highly specific manner. In this review, we summarise the roles of PP2A in cardiac physiology and disease. PP2A modulates numerous processes that are vital for heart function including calcium handling, contractility, β-adrenergic signalling, metabolism and transcription. Dysregulation of PP2A has been observed in human cardiac disease settings, including heart failure and atrial fibrillation. Efforts are underway, particularly in the cancer field, to develop therapeutics targeting PP2A activity. The development of small molecule activators of PP2A (SMAPs) and other compounds that selectively target specific PP2A holoenzymes (e.g. PP2A/B56α and PP2A/B56ε) will improve understanding of the function of different PP2A species in the heart, and may lead to the development of therapeutics for normalising aberrant protein phosphorylation in settings of cardiac remodelling and dysfunction.
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Affiliation(s)
- Nicola M Sergienko
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Central Clinical School, Monash University, Clayton VIC 3800, Australia
| | - Daniel G Donner
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Baker Department of Cardiometabolic Health, The University of Melbourne, Parkville VIC 3010, Australia
| | - Lea M D Delbridge
- Department of Anatomy and Physiology, The University of Melbourne, Parkville VIC 3010, Australia
| | - Julie R McMullen
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Baker Department of Cardiometabolic Health, The University of Melbourne, Parkville VIC 3010, Australia; Department of Physiology and Department of Medicine Alfred Hospital, Monash University, Clayton VIC 3800, Australia; Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora VIC 3086, Australia; Department of Diabetes, Central Clinical School, Monash University, Clayton VIC 3800, Australia.
| | - Kate L Weeks
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Department of Anatomy and Physiology, The University of Melbourne, Parkville VIC 3010, Australia; Baker Department of Cardiometabolic Health, The University of Melbourne, Parkville VIC 3010, Australia; Department of Diabetes, Central Clinical School, Monash University, Clayton VIC 3800, Australia.
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Martin TG, Myers VD, Dubey P, Dubey S, Perez E, Moravec CS, Willis MS, Feldman AM, Kirk JA. Cardiomyocyte contractile impairment in heart failure results from reduced BAG3-mediated sarcomeric protein turnover. Nat Commun 2021; 12:2942. [PMID: 34011988 PMCID: PMC8134551 DOI: 10.1038/s41467-021-23272-z] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Accepted: 04/22/2021] [Indexed: 12/22/2022] Open
Abstract
The association between reduced myofilament force-generating capacity (Fmax) and heart failure (HF) is clear, however the underlying molecular mechanisms are poorly understood. Here, we show impaired Fmax arises from reduced BAG3-mediated sarcomere turnover. Myofilament BAG3 expression decreases in human HF and positively correlates with Fmax. We confirm this relationship using BAG3 haploinsufficient mice, which display reduced Fmax and increased myofilament ubiquitination, suggesting impaired protein turnover. We show cardiac BAG3 operates via chaperone-assisted selective autophagy (CASA), conserved from skeletal muscle, and confirm sarcomeric CASA complex localization is BAG3/proteotoxic stress-dependent. Using mass spectrometry, we characterize the myofilament CASA interactome in the human heart and identify eight clients of BAG3-mediated turnover. To determine if increasing BAG3 expression in HF can restore sarcomere proteostasis/Fmax, HF mice were treated with rAAV9-BAG3. Gene therapy fully rescued Fmax and CASA protein turnover after four weeks. Our findings indicate BAG3-mediated sarcomere turnover is fundamental for myofilament functional maintenance. Decreased expression of BAG3 in the heart is associated with contractile dysfunction and heart failure. Here the authors show that this is due to decreased BAG3-dependent sarcomere protein turnover, which impairs mechanical function, and that sarcomere force-generating capacity is restored with BAG3 gene therapy.
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Affiliation(s)
- Thomas G Martin
- Department of Cell and Molecular Physiology, Loyola University Stritch School of Medicine, Maywood, IL, USA
| | - Valerie D Myers
- Department of Medicine, Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - Praveen Dubey
- Department of Medicine, Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - Shubham Dubey
- Department of Medicine, Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - Edith Perez
- Department of Cell and Molecular Physiology, Loyola University Stritch School of Medicine, Maywood, IL, USA
| | - Christine S Moravec
- Department of Medicine, Cleveland Clinic Lerner College of Medicine, Cleveland, OH, USA
| | - Monte S Willis
- Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Arthur M Feldman
- Department of Medicine, Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - Jonathan A Kirk
- Department of Cell and Molecular Physiology, Loyola University Stritch School of Medicine, Maywood, IL, USA.
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Structure and proteolytic susceptibility of the inhibitory C-terminal tail of cardiac troponin I. Biochim Biophys Acta Gen Subj 2019; 1863:661-671. [DOI: 10.1016/j.bbagen.2019.01.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 11/22/2018] [Accepted: 01/14/2019] [Indexed: 01/17/2023]
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van der Velden J, Stienen GJM. Cardiac Disorders and Pathophysiology of Sarcomeric Proteins. Physiol Rev 2019; 99:381-426. [PMID: 30379622 DOI: 10.1152/physrev.00040.2017] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The sarcomeric proteins represent the structural building blocks of heart muscle, which are essential for contraction and relaxation. During recent years, it has become evident that posttranslational modifications of sarcomeric proteins, in particular phosphorylation, tune cardiac pump function at rest and during exercise. This delicate, orchestrated interaction is also influenced by mutations, predominantly in sarcomeric proteins, which cause hypertrophic or dilated cardiomyopathy. In this review, we follow a bottom-up approach starting from a description of the basic components of cardiac muscle at the molecular level up to the various forms of cardiac disorders at the organ level. An overview is given of sarcomere changes in acquired and inherited forms of cardiac disease and the underlying disease mechanisms with particular reference to human tissue. A distinction will be made between the primary defect and maladaptive/adaptive secondary changes. Techniques used to unravel functional consequences of disease-induced protein changes are described, and an overview of current and future treatments targeted at sarcomeric proteins is given. The current evidence presented suggests that sarcomeres not only form the basis of cardiac muscle function but also represent a therapeutic target to combat cardiac disease.
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Affiliation(s)
- Jolanda van der Velden
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, Amsterdam , The Netherlands ; and Department of Physiology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Ger J M Stienen
- Amsterdam UMC, Vrije Universiteit Amsterdam, Physiology, Amsterdam Cardiovascular Sciences, Amsterdam , The Netherlands ; and Department of Physiology, Kilimanjaro Christian Medical University College, Moshi, Tanzania
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