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Singh S, Jangid RK, Crowder A, Groves AK. Foxi3 transcription factor activity is mediated by a C-terminal transactivation domain and regulated by the Protein Phosphatase 2A (PP2A) complex. Sci Rep 2018; 8:17249. [PMID: 30467319 PMCID: PMC6250667 DOI: 10.1038/s41598-018-35390-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 11/02/2018] [Indexed: 01/20/2023] Open
Abstract
The Forkhead box (FOX) family consists of at least 19 subgroups of transcription factors which are characterized by the presence of an evolutionary conserved ‘forkhead’ or ‘winged-helix’ DNA-binding domain. Despite having a conserved core DNA binding domain, FOX proteins display remarkable functional diversity and are involved in many developmental and cell specific processes. In the present study, we focus on a poorly characterized member of the Forkhead family, Foxi3, which plays a critical role in the development of the inner ear and jaw. We show that Foxi3 contains at least two important functional domains, a nuclear localization sequence (NLS) and a C-terminal transactivation domain (TAD), and that it directly binds its targets in a sequence specific manner. We also show that the transcriptional activity of Foxi3 is regulated by phosphorylation, and that the activity of Foxi3 can be attenuated by its physical interaction with the protein phosphatase 2A (PP2A) complex.
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Affiliation(s)
- Sunita Singh
- Department of Neuroscience, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Rahul K Jangid
- Department of Neuroscience, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Alyssa Crowder
- Department of Neuroscience, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA
| | - Andrew K Groves
- Department of Neuroscience, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA. .,Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA. .,Program in Developmental Biology, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA.
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52
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Koyani CN, Trummer C, Shrestha N, Scheruebel S, Bourgeois B, Plastira I, Kickmaier S, Sourij H, Rainer PP, Madl T, Sattler W, Pelzmann B, Malle E, von Lewinski D. Saxagliptin but Not Sitagliptin Inhibits CaMKII and PKC via DPP9 Inhibition in Cardiomyocytes. Front Physiol 2018; 9:1622. [PMID: 30487758 PMCID: PMC6246635 DOI: 10.3389/fphys.2018.01622] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 10/26/2018] [Indexed: 01/18/2023] Open
Abstract
Some oral anti-hyperglycemic drugs, including gliptins that inhibit dipeptidyl peptidase 4 (DPP4), have been linked to the increased risk of heart failure (HF) in type-2 diabetic patients. While the cardiovascular safety trial, TECOS, revealed no link between sitagliptin and the risk of HF, a substantial 27% increase in the hospitalization for HF was observed in type-2 diabetic patients treated with saxagliptin within the SAVOR-TIMI 53 trial. A previous in vitro study revealed that saxagliptin impairs the Ca2+/calmodulin-dependent protein kinase II (CaMKII)-phospholamban (PLB)-sarcoplasmic reticulum Ca2+-ATPase 2a axis and protein kinase C (PKC) activity in cardiomyocytes leading to impaired cardiac contractility and electrophysiological function. However, the link between saxagliptin and its target proteins (CaMKII and PKC) remains to be explored. Since DPP8 and DPP9 (but not DPP4) are expressed by cardiomyocytes and saxagliptin is internalized by cardiomyocytes, we investigated whether DPP8/9 contribute to saxagliptin-mediated inhibition of CaMKII and PKC activity. Structural analysis revealed that the DPP4-saxagliptin interaction motif (S630, Y547) for the cyanopyrrolidine group is conserved in DPP8 (S755, Y669) and DPP9 (S730, Y644). Conversely, F357 that facilitates binding of the anchor lock domain of sitagliptin in the S2 extensive subsite of DPP4 is not conserved in DPP8/9. In parallel, unlike saxagliptin, sitagliptin did not affect phosphorylation of CaMKII/PLB or activity of PKC in HL-1 cardiomyocytes. These findings were recapitulated by pharmacological inhibition (TC-E-5007, a DPP8/9 antagonist) and knock-down of DPP9 (but not DPP8). In primary mouse ventricular cardiomyocytes, saxagliptin (but not sitagliptin) impaired Ca2+ transient relaxation and prolonged action potential duration (APD). These results suggest that saxagliptin-DPP9 interaction impairs the CaMKII-PLB and PKC signaling in cardiomyocytes. We reveal a novel and potential role of DPP9 in cardiac signaling. The interaction of saxagliptin with DPP9 may represent an underlying mechanism for the link between saxagliptin and HF. Elucidation of saxagliptin-DPP9 interaction and downstream events may foster a better understanding of the role of gliptins as modulators of cardiac signaling.
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Affiliation(s)
| | - Christopher Trummer
- Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
| | - Niroj Shrestha
- Biophysics, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
| | - Susanne Scheruebel
- Biophysics, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
| | - Benjamin Bourgeois
- Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
| | - Ioanna Plastira
- Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
| | - Sandra Kickmaier
- Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
| | - Harald Sourij
- Division of Endocrinology and Diabetology, Department of Internal Medicine, Medical University of Graz, Graz, Austria
- Center for Biomarker Research in Medicine, Graz, Austria
| | - Peter P. Rainer
- Division of Cardiology, Medical University of Graz, Graz, Austria
| | - Tobias Madl
- Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
- BioTechMed-Graz, Graz, Austria
| | - Wolfgang Sattler
- Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
| | - Brigitte Pelzmann
- Biophysics, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
| | - Ernst Malle
- Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria
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53
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Mazhar S, Taylor SE, Sangodkar J, Narla G. Targeting PP2A in cancer: Combination therapies. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1866:51-63. [PMID: 30401535 DOI: 10.1016/j.bbamcr.2018.08.020] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 08/21/2018] [Accepted: 08/28/2018] [Indexed: 12/12/2022]
Abstract
The serine/threonine phosphatase PP2A regulates a vast portion of the phosphoproteome including pathways involved in apoptosis, proliferation and DNA damage response and PP2A inactivation is a vital step in malignant transformation. Many groups have explored the therapeutic venue of combining PP2A reactivation with kinase inhibition to counteract the very changes in tumor suppressors and oncogenes that lead to cancer development. Conversely, inhibition of PP2A to complement chemotherapy and radiation-induced cancer cell death is also an area of active investigation. Here we review the studies that utilize PP2A targeted agents as combination therapy in cancer. A potential role for PP2A in tumor immunity is also highlighted.
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Affiliation(s)
- Sahar Mazhar
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Sarah E Taylor
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Jaya Sangodkar
- Division of Genetic Medicine, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Goutham Narla
- Division of Genetic Medicine, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA.
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54
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Shimizu Y, Polavarapu R, Eskla KL, Nicholson CK, Koczor CA, Wang R, Lewis W, Shiva S, Lefer DJ, Calvert JW. Hydrogen sulfide regulates cardiac mitochondrial biogenesis via the activation of AMPK. J Mol Cell Cardiol 2018; 116:29-40. [PMID: 29408195 DOI: 10.1016/j.yjmcc.2018.01.011] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 01/03/2018] [Accepted: 01/18/2018] [Indexed: 12/13/2022]
Abstract
BACKGROUND Hydrogen sulfide (H2S) is an important regulator of mitochondrial bioenergetics, but its role in regulating mitochondrial biogenesis is not well understood. Using both genetic and pharmacological approaches, we sought to determine if H2S levels directly influenced cardiac mitochondrial content. RESULTS Mice deficient in the H2S-producing enzyme, cystathionine γ-lyase (CSE KO) displayed diminished cardiac mitochondrial content when compared to wild-type hearts. In contrast, mice overexpressing CSE (CSE Tg) and mice supplemented with the orally active H2S-releasing prodrug, SG-1002, displayed enhanced cardiac mitochondrial content. Additional analysis revealed that cardiac H2S levels influenced the nuclear localization and transcriptional activity of peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) with higher levels having a positive influence and lower levels having a negative influence. Studies aimed at evaluating the underlying mechanisms found that H2S required AMP-activated protein kinase (AMPK) to induce PGC1α signaling and mitochondrial biogenesis. Finally, we found that restoring H2S levels with SG-1002 in the setting of heart failure increased cardiac mitochondrial content, improved mitochondrial respiration, improved ATP production efficiency, and improved cardiac function. CONCLUSIONS Together, these results suggest that hydrogen sulfide is an important regulator of cardiac mitochondrial content and establishes that exogenous hydrogen sulfide can induce mitochondrial biogenesis via an AMPK-PGC1α signaling cascade.
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Affiliation(s)
- Yuuki Shimizu
- Department of Surgery, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University School of Medicine, Atlanta, GA, USA
| | - Rohini Polavarapu
- Department of Surgery, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University School of Medicine, Atlanta, GA, USA
| | - Kattri-Liis Eskla
- Department of Surgery, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University School of Medicine, Atlanta, GA, USA
| | - Chad K Nicholson
- Department of Surgery, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University School of Medicine, Atlanta, GA, USA
| | | | - Rui Wang
- Cardiovascular and Metabolic Research Unit, Laurentian University, Sudbury, Canada
| | - William Lewis
- Department of Pathology, Emory University School of Medicine, Atlanta, GA, USA
| | - Sruti Shiva
- Department of Pharmacology & Chemical Biology, Vascular Medicine Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - David J Lefer
- Cardiovascular Center of Excellence, Department of Pharmacology, LSU Health Sciences Center, New Orleans, LA, USA
| | - John W Calvert
- Department of Surgery, Division of Cardiothoracic Surgery, Carlyle Fraser Heart Center, Emory University School of Medicine, Atlanta, GA, USA.
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Protein phosphatase 5 regulates titin phosphorylation and function at a sarcomere-associated mechanosensor complex in cardiomyocytes. Nat Commun 2018; 9:262. [PMID: 29343782 PMCID: PMC5772059 DOI: 10.1038/s41467-017-02483-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 12/04/2017] [Indexed: 12/14/2022] Open
Abstract
Serine/threonine protein phosphatase 5 (PP5) is ubiquitously expressed in eukaryotic cells; however, its function in cardiomyocytes is unknown. Under basal conditions, PP5 is autoinhibited, but enzymatic activity rises upon binding of specific factors, such as the chaperone Hsp90. Here we show that PP5 binds and dephosphorylates the elastic N2B-unique sequence (N2Bus) of titin in cardiomyocytes. Using various binding and phosphorylation tests, cell-culture manipulation, and transgenic mouse hearts, we demonstrate that PP5 associates with N2Bus in vitro and in sarcomeres and is antagonistic to several protein kinases, which phosphorylate N2Bus and lower titin-based passive tension. PP5 is pathologically elevated and likely contributes to hypo-phosphorylation of N2Bus in failing human hearts. Furthermore, Hsp90-activated PP5 interacts with components of a sarcomeric, N2Bus-associated, mechanosensor complex, and blocks mitogen-activated protein-kinase signaling in this complex. Our work establishes PP5 as a compartmentalized, well-controlled phosphatase in cardiomyocytes, which regulates titin properties and kinase signaling at the myofilaments. Protein phosphatase 5 (PP5) is expressed in many cell types but its role in cardiomyocytes is unknown. Here the authors show that PP5 binds and dephosphorylates elastic titin in cardiac sarcomeres, and that PP5 is increased in heart failure, reducing cardiomyocyte compliance.
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