The E3 ubiquitin ligase Asb2β is downregulated in a mouse model of hypertrophic cardiomyopathy and targets desmin for proteasomal degradation.
BACKGROUND
Hypertrophic cardiomyopathy (HCM) is an autosomal-dominant disease with mutations in genes encoding sarcomeric proteins. Previous findings suggest deregulation of the ubiquitin proteasome system (UPS) in HCM in humans and in a mouse model of HCM (Mybpc3-targeted knock-in (KI) mice). In this study we investigated transcript levels of several muscle-specific E3 ubiquitin ligases in KI mice and aimed at identifying novel protein targets.


RESULTS
Out of 9 muscle-specific E3 ligases, Asb2β was found with the lowest mRNA level in KI compared to wild-type (WT) mice. After adenoviral-mediated Asb2β transduction of WT neonatal mouse cardiomyocytes with either a WT or inactive Asb2β mutant, desmin was identified as a new target of Asb2β by mass spectrometry, co-immunoprecipitation and immunoblotting. Immunofluorescence analysis revealed a co-localization of desmin with Asb2β at the Z-disk of the sarcomere. Knock-down of Asb2β in cardiomyocytes resulted in higher desmin protein levels. Furthermore, desmin levels were higher in ventricular samples of HCM mice and patients than controls.


CONCLUSIONS
This study identifies desmin as a new Asb2β target for proteasomal degradation in cardiomyocytes and suggests that accumulation of desmin could contribute to UPS impairment in HCM mice and patients.
Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;; DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Germany;; University Heart Center Hamburg, Hamburg, Germany;
Tilo
T
Thottakara
Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;; DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Germany;. Electronic address: f.friedrich@uke.de.
Felix W
FW
Friedrich
Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;; DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Germany;
Silke
S
Reischmann
Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;; DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Germany;
Simon
S
Braumann
Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;; DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Germany;
Saskia
S
Schlossarek
Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;; DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Germany;
Elisabeth
E
Krämer
Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
Denise
D
Juhr
Institute of Clinical Chemistry, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
Hartmut
H
Schlüter
Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, the Netherlands; ICIN-Netherlands Heart Institute, Utrecht, the Netherlands.
Jolanda
J
van der Velden
DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Germany;; University Heart Center Hamburg, Hamburg, Germany;
Julia
J
Münch
DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Germany;; University Heart Center Hamburg, Hamburg, Germany;
Monica
M
Patten
Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;; DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Germany;
Thomas
T
Eschenhagen
Institut de Pharmacologie et de Biologie Structurale, CNRS, Toulouse, France;; Université de Toulouse, UPS, Toulouse, France.
Christel
C
Moog-Lutz
Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;; DZHK (German Centre for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Germany;. Electronic address: l.carrier@uke.de.
Lucie
L
Carrier
D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics* / Q000473:pathology; D003893:Desmin / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D009154:Mutation; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D059748:Proteolysis; D012518:Sarcomeres / Q000378:metabolism; D050826:Suppressor of Cytokine Signaling Proteins; D025801:Ubiquitin
D048868:Adaptor Proteins, Signal Transducing; C542087:Asb2 protein, mouse; D003893:Desmin; D050826:Suppressor of Cytokine Signaling Proteins; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex
Asb2β; Desmin; E3 ubiquitin ligase; Filamin B; Hypertrophic cardiomyopathy; Proteasome