title: Impairment of immunoproteasome function by β5i/LMP7 subunit deficiency results in severe enterovirus myocarditis.
abstract: Proteasomes recognize and degrade poly-ubiquitinylated proteins. In infectious disease, cells activated by interferons (IFNs) express three unique catalytic subunits β1i/LMP2, β2i/MECL-1 and β5i/LMP7 forming an alternative proteasome isoform, the immunoproteasome (IP). The in vivo function of IPs in pathogen-induced inflammation is still a matter of controversy. IPs were mainly associated with MHC class I antigen processing. However, recent findings pointed to a more general function of IPs in response to cytokine stress. Here, we report on the role of IPs in acute coxsackievirus B3 (CVB3) myocarditis reflecting one of the most common viral disease entities among young people. Despite identical viral load in both control and IP-deficient mice, IP-deficiency was associated with severe acute heart muscle injury reflected by large foci of inflammatory lesions and severe myocardial tissue damage. Exacerbation of acute heart muscle injury in this host was ascribed to disequilibrium in protein homeostasis in viral heart disease as indicated by the detection of increased proteotoxic stress in cytokine-challenged cardiomyocytes and inflammatory cells from IP-deficient mice. In fact, due to IP-dependent removal of poly-ubiquitinylated protein aggregates in the injured myocardium IPs protected CVB3-challenged mice from oxidant-protein damage. Impaired NFκB activation in IP-deficient cardiomyocytes and inflammatory cells and proteotoxic stress in combination with severe inflammation in CVB3-challenged hearts from IP-deficient mice potentiated apoptotic cell death in this host, thus exacerbating acute tissue damage. Adoptive T cell transfer studies in IP-deficient mice are in agreement with data pointing towards an effective CD8 T cell immune. This study therefore demonstrates that IP formation primarily protects the target organ of CVB3 infection from excessive inflammatory tissue damage in a virus-induced proinflammatory cytokine milieu.
authors: Medizinische Klinik für Kardiologie, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors: Elisa
authors: E
authors: Opitz
authors: Annett
authors: A
authors: Koch
authors: Karin
authors: K
authors: Klingel
authors: Frank
authors: F
authors: Schmidt
authors: Stefan
authors: S
authors: Prokop
authors: Anna
authors: A
authors: Rahnefeld
authors: Martina
authors: M
authors: Sauter
authors: Frank L
authors: FL
authors: Heppner
authors: Uwe
authors: U
authors: Völker
authors: Reinhard
authors: R
authors: Kandolf
authors: Ulrike
authors: U
authors: Kuckelkorn
authors: Karl
authors: K
authors: Stangl
authors: Elke
authors: E
authors: Krüger
authors: Peter M
authors: PM
authors: Kloetzel
authors: Antje
authors: A
authors: Voigt
mesh_terms: D000818:Animals; D017209:Apoptosis; D003384:Coxsackievirus Infections / Q000276:immunology* / Q000473:pathology; D029822:Enterovirus B, Human; D051379:Mice; D009205:Myocarditis / Q000276:immunology* / Q000473:pathology / Q000821:virology; D025821:Polyubiquitin / Q000276:immunology; D046988:Proteasome Endopeptidase Complex / Q000172:deficiency* / Q000276:immunology*; D021122:Protein Subunits / Q000172:deficiency*
chemical_list: D021122:Protein Subunits; D025821:Polyubiquitin; D046988:Proteasome Endopeptidase Complex