title: Sumo E2 enzyme UBC9 is required for efficient protein quality control in cardiomyocytes.
abstract: BACKGROUND
  Impairment of proteasomal function is pathogenic in several cardiac proteinopathies and can eventually lead to heart failure. Loss of proteasomal activity often results in the accumulation of large protein aggregates. The ubiquitin proteasome system (UPS) is primarily responsible for cellular protein degradation, and although the role of ubiquitination in this process is well studied, the function of an ancillary post-translational modification, SUMOylation, in protein quality control is not fully understood.
  
  
  OBJECTIVE
  To determine the role of ubiquitin-conjugating enzyme 9 (UBC9), a small ubiquitin-like modifier-conjugating enzyme, in cardiomyocyte protein quality control.
  
  
  RESULTS
  Gain- and loss-of-function approaches were used to determine the importance of UBC9. Overexpression of UBC9 enhanced UPS function in cardiomyocytes, whereas knockdown of UBC9 by small interfering RNA caused significant accumulations of aggregated protein. UPS function and relative activity was analyzed using a UPS reporter protein consisting of a short degron, CL1, fused to the COOH-terminus of green fluorescent protein (GFPu). Subsequently, the effects of UBC9 on UPS function were tested in a proteotoxic model of desmin-related cardiomyopathy, caused by cardiomyocyte-specific expression of a mutated αB crystallin, CryAB(R120G). CryAB(R120G) expression leads to aggregate formation and decreased proteasomal function. Coinfection of UBC9-adenovirus with CryAB(R120G) virus reduced the proteotoxic sequelae, decreasing overall aggregate concentrations. Conversely, knockdown of UBC9 significantly decreased UPS function in the model and resulted in increased aggregate levels.
  
  
  CONCLUSIONS
  UBC9 plays a significant role in cardiomyocyte protein quality control, and its activity can be exploited to reduce toxic levels of misfolded or aggregated proteins in cardiomyopathy.
authors.affiliation: From the Heart Institute, Department of Pediatrics, The Cincinnati Children's Hospital Medical Center, OH (M.K.G., J.G., R.L., J.D.M., J.R.); and Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion (X.W.).
authors.forename: Manish K
authors.initials: MK
authors.lastname: Gupta
authors.affiliation: From the Heart Institute, Department of Pediatrics, The Cincinnati Children's Hospital Medical Center, OH (M.K.G., J.G., R.L., J.D.M., J.R.); and Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion (X.W.).
authors.forename: James
authors.initials: J
authors.lastname: Gulick
authors.affiliation: From the Heart Institute, Department of Pediatrics, The Cincinnati Children's Hospital Medical Center, OH (M.K.G., J.G., R.L., J.D.M., J.R.); and Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion (X.W.).
authors.forename: Ruijie
authors.initials: R
authors.lastname: Liu
authors.affiliation: From the Heart Institute, Department of Pediatrics, The Cincinnati Children's Hospital Medical Center, OH (M.K.G., J.G., R.L., J.D.M., J.R.); and Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion (X.W.).
authors.forename: Xuejun
authors.initials: X
authors.lastname: Wang
authors.affiliation: From the Heart Institute, Department of Pediatrics, The Cincinnati Children's Hospital Medical Center, OH (M.K.G., J.G., R.L., J.D.M., J.R.); and Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion (X.W.).
authors.forename: Jeffery D
authors.initials: JD
authors.lastname: Molkentin
authors.affiliation: From the Heart Institute, Department of Pediatrics, The Cincinnati Children's Hospital Medical Center, OH (M.K.G., J.G., R.L., J.D.M., J.R.); and Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion (X.W.). jeff.robbins@cchmc.org.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Robbins
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D009202:Cardiomyopathies / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D009154:Mutation; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D061251:Primary Cell Culture; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D059748:Proteolysis; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D058207:Sumoylation; D025801:Ubiquitin / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D038203:alpha-Crystallin B Chain / Q000235:genetics / Q000378:metabolism; D000098843:Ubiquitin-Conjugating Enzyme UBC9
chemical_list: D025801:Ubiquitin; D038203:alpha-Crystallin B Chain; D049452:Green Fluorescent Proteins; D044763:Ubiquitin-Conjugating Enzymes; D046988:Proteasome Endopeptidase Complex; D000098843:Ubiquitin-Conjugating Enzyme UBC9
keywords: autophagy; cardiomyopathies; proteasome endopeptidase complex
references.citation: Circ Res. 2004 Jan 9;94(1):110-8
references.pmid: 14656927
references.citation: Circ Res. 2013 Mar 29;112(7):1046-58
references.pmid: 23538275
references.citation: Neurotox Res. 2013 Jan;23(1):1-21
references.pmid: 23229893
references.citation: Proc Natl Acad Sci U S A. 2007 Apr 3;104(14):5995-6000
references.pmid: 17389375
references.citation: Mol Biol Cell. 2013 Jan;24(2):74-84
references.pmid: 23155000
references.citation: Circulation. 2008 May 27;117(21):2743-51
references.pmid: 18490523
references.citation: Biochem Soc Trans. 2008 Oct;36(Pt 5):874-8
references.pmid: 18793154
references.citation: J Biol Chem. 2009 Aug 7;284(32):21296-306
references.pmid: 19497852
references.citation: Nat Rev Mol Cell Biol. 2009 Aug;10(8):564-8
references.pmid: 19474794
references.citation: Trends Genet. 2003 May;19(5):233-8
references.pmid: 12711212
references.citation: J Cell Biol. 2011 Jul 11;194(1):49-60
references.pmid: 21746851
references.citation: Mol Cell. 2014 Mar 20;53(6):1053-66
references.pmid: 24582501
references.citation: J Cell Sci. 2012 Feb 1;125(Pt 3):539-48
references.pmid: 22389393
references.citation: Acta Neuropathol Commun. 2013 Dec 05;1:79
references.pmid: 24314025
references.citation: J Clin Invest. 2011 Sep;121(9):3689-700
references.pmid: 21841311
references.citation: Am J Physiol Heart Circ Physiol. 2012 Jul;303(1):H9-18
references.pmid: 22523251
references.citation: FASEB J. 2006 Feb;20(2):362-4
references.pmid: 16371426
references.citation: Circ Res. 2006 May 12;98(9):1186-93
references.pmid: 16601230
references.citation: J Cell Sci. 2009 Mar 15;122(Pt 6):775-9
references.pmid: 19223394
references.citation: Mol Biol Cell. 2010 Dec;21(23):4227-39
references.pmid: 20943951
references.citation: Nature. 2011 Sep 07;477(7366):601-5
references.pmid: 21900893
references.citation: Circ Res. 2010 Jul 9;107(1):19-29
references.pmid: 20616338
references.citation: Semin Pediatr Neurol. 2011 Dec;18(4):272-6
references.pmid: 22172423
references.citation: J Cell Biol. 2002 Apr 1;157(1):125-36
references.pmid: 11927605
references.citation: Mol Cell. 2013 Sep 26;51(6):819-28
references.pmid: 24035499
references.citation: N Engl J Med. 2013 Jan 31;368(5):455-64
references.pmid: 23363499
references.citation: Proc Natl Acad Sci U S A. 2004 Jul 6;101(27):10132-6
references.pmid: 15220483
references.citation: Circulation. 2005 Nov 29;112(22):3451-61
references.pmid: 16316967
references.citation: Expert Opin Ther Targets. 2005 Dec;9(6):1203-16
references.pmid: 16300471
references.citation: PLoS One. 2012;7(12):e51672
references.pmid: 23284737
references.citation: FEBS J. 2013 Sep;280(18):4430-8
references.pmid: 23809253
references.citation: Cell Rep. 2013 Jul 25;4(2):362-75
references.pmid: 23871671
references.citation: Annu Rev Biochem. 2013;82:357-85
references.pmid: 23746258
references.citation: Subcell Biochem. 2010;54:195-214
references.pmid: 21222284
references.citation: Cell Struct Funct. 2013;38(1):67-79
references.pmid: 23470653
references.citation: J Mol Cell Cardiol. 2014 Jun;71:3-10
references.pmid: 24380730
references.citation: Circ Res. 2011 Jul 8;109(2):151-60
references.pmid: 21617129
references.citation: Cell. 1994 Sep 9;78(5):761-71
references.pmid: 8087844
references.citation: Circ Res. 2001 Jul 6;89(1):84-91
references.pmid: 11440982
references.citation: Circ Res. 2005 Nov 11;97(10):1018-26
references.pmid: 16210548
references.citation: Cell. 2013 Jul 3;154(1):134-45
references.pmid: 23791384
references.citation: Dev Cell. 2005 Dec;9(6):769-79
references.pmid: 16326389
references.citation: Sci Signal. 2011 Jun 21;4(178):rs4
references.pmid: 21693764
references.citation: Circ Res. 2011 Jul 8;109(2):141-50
references.pmid: 21597010
references.citation: Mol Cell. 2005 Feb 4;17(3):351-65
references.pmid: 15694337
references.citation: Cell. 2007 Aug 10;130(3):427-39
references.pmid: 17693254
references.citation: Arterioscler Thromb Vasc Biol. 2011 Jul;31(7):1634-42
references.pmid: 21527745
references.citation: Science. 2003 Apr 18;300(5618):486-9
references.pmid: 12702875
references.citation: J Mol Cell Cardiol. 2012 Mar;52(3):638-49
references.pmid: 22155005
references.citation: Exp Cell Res. 2000 Mar 15;255(2):135-43
references.pmid: 10694430
references.citation: Prog Mol Biol Transl Sci. 2012;109:295-346
references.pmid: 22727426
references.citation: Biochem Biophys Res Commun. 2008 Oct 3;374(4):673-8
references.pmid: 18675254
references.citation: J Biol Chem. 2001 May 4;276(18):15306-15
references.pmid: 11278694
references.citation: Am J Physiol Heart Circ Physiol. 2011 Dec;301(6):H2207-19
references.pmid: 21949118
references.citation: Proc Natl Acad Sci U S A. 2005 Sep 20;102(38):13592-7
references.pmid: 16155124
references.citation: Am J Physiol Heart Circ Physiol. 2004 Sep;287(3):H1417-25
references.pmid: 15105173
references.citation: Am J Physiol Heart Circ Physiol. 2013 Feb 1;304(3):H337-49
references.pmid: 23220331
references.citation: J Biol Chem. 1997 May 16;272(20):13437-45
references.pmid: 9148969