Balancing protein turnover in the heart
Alterations in the ubiquitin proteasome system (UPS), which tags proteins for degradation, underlies some cardiomyopathies and age-related cardiac dysfunction. In the heart, the UPS is essential for the precise balance between cardiomyocyte atrophy and hypertrophy. In skeletal muscle, the E3 ubiquitin ligase atrogin-1 promotes atrophy by targeting hypertrophy-associated proteins for degradation; however, a role for atrogin-1 in cardiac proteostasis is not clear. In this issue of the Journal of Clinical Investigation, Marco Sandri, Marco Mongillo and colleagues at the Venetian Institute of Molecular Medicine investigated cardiac homeostasis in atrogin-1-deficient mice. Aged animals lacking atrogin-1 exhibited enlarged and abnormally shaped hearts, thickened left ventricular walls, increased fibrosis and apoptosis, and reduced function. Loss of atrogin-1 led to increased ER stress and upregulation of genes involved in the unfolded protein response (UPR). Moreover, autophagy, which is inhibited by the UPR in skeletal muscle, was also repressed in cardiac tissue of atrogin-1 null animals, suggesting that atrogin-1 may target autophagy-related proteins for degradation. Evaluation of cardiac protein turnover in atrogin-1-deficient animals revealed reduced turnover of lysosomal targets, including the endosomal sorting complex III protein CHMP2B. Silencing CHMP2B in atrogin-1 null mice restored markers of autophagy and reduced apoptosis in the heart. These results indicated that UPS-regulated autophagy in the protein turnover necessary for cardiomyocyte health.
TITLE: Atrogin-1 deficiency promotes cardiomyopathy and premature death via impaired autophagy
AUTHOR CONTACT:
Marco Sandri
Venetian Institute of Molecular Medicine, Padova, UNK, ITA
Phone: +39 049 7923258; Fax: +39 049 7923250; E-mail: marco.sandri@unipd.it
Or
Marco Mongillo
Venetian Institute of Molecular Medicine, Padova, UNK, ITA
Phone: 390497923229; Fax: 390497923250, E-mail: marco.mongillo@unipd.i
View this article at: http://www.jci.org/articles/view/66339
Protecting the kidney from hypoxia-induced damage
Acute hypoxia-induced renal injury often progresses to chronic kidney disease (CKD), and the progressive loss of kidney function in CKD is linked to endothelial cell (EC) damage. The hypoxia-inducible transcription factors HIF-1 and HIF-2 are expressed in renal ECs following ischemic injury, but the specific contributions of these mediators to pathogenesis are not clear. In this issue of the Journal of Clinical Investigation, Volker Haase and colleagues at the Vanderbilt University School of Medicine used murine models of hypoxic kidney injury, to evaluate the contribution of endothelial HIF-1 and HIF-2 toward the development of ischemia-induced pathogenesis. Loss of HIF-2 alone markedly increased kidney inflammation and fibrosis following ischemic injury and was associated with increased expression of the neutrophil adhesion molecule VCAM1. Blocking VCAM1 in HIF-2-deficient mice reduced hypoxia-associated phenotypes. Furthermore, enhancing HIF-2 activation in WT mice prior to ischemia and reperfusion protected animals from kidney injury. Together, these data indicate that endothelial HIF-2 protects kidney from hypoxia-induced damage.
TITLE: Endothelial HIF-2 mediates protection and recovery from ischemic kidney injury
AUTHOR CONTACT:
Volker Hans Haase
Vanderbilt University, Nashville, TN, USA
Phone: 615 343-7254; Fax: 615 322-6854; E-mail: volker.haase@vanderbilt.edu
View this article at: http://www.jci.org/articles/view/69073
BONE BIOLOGY
TITLE: Bicc1 is a genetic determinant of osteoblastogenesis and bone mineral density
AUTHOR CONTACT:
Charles Farber
University of Virgina, Charlottesville, VA, USA
Phone: 434-243-8584; E-mail: crf2s@virginia.edu
View this article at: http://www.jci.org/articles/view/73072
ENDOCRINOLOGY
TITLE: MicroRNA-7a regulates pancreatic β cell function
AUTHOR CONTACT:
Markus Stoffel
Institute of Molecular Health Sciences, ETH Zurich, Zurich, UNK, CHE
Phone: +41 44 633 4560; E-mail: stoffel@biol.ethz.ch
View this article at: http://www.jci.org/articles/view/73066
IMMUNOLOGY
TITLE: MHC-derived allopeptide activates TCR-biased CD8+ Tregs and suppresses organ rejection
AUTHOR CONTACT:
Carole Guillonneau
INSERM UMR1064, Nantes, FRA
Phone: 33 02 40 08 75 96; E-mail: Carole.Guillonneau@univ-nantes.fr
View this article at: http://www.jci.org/articles/view/71533
TITLE: ER stress regulates myeloid-derived suppressor cell fate through TRAIL-R–mediated apoptosis
AUTHOR CONTACT:
Dmitry I. Gabrilovich
The Wistar Institute, Philadelphia, PA, USA
Phone: 215-495-6955; Fax: ; E-mail: dgabrilovich@wistar.org
View this article at: http://www.jci.org/articles/view/74056
MUSCLE BIOLOGY
TITLE: MicroRNA-486–dependent modulation of DOCK3/PTEN/AKT signaling pathways improves muscular dystrophy–associated symptoms
AUTHOR CONTACT:
Louis Kunkel
Boston Children's Hospital/Harvard Medical School, Boston, MA, USA
Phone: 617.355.6729; Fax: 617.730.0253; E-mail: kunkel@enders.tch.harvard.edu.
View this article at: http://www.jci.org/articles/view/73579
VIROLOGY
TITLE: Type I IFN signaling in CD8– DCs impairs Th1-dependent malaria immunity
AUTHOR CONTACT:
Ashraful Haque
Queensland Institute of Medical Research, Brisbane, UNK, AUS
Phone: +61738453948; Fax: +61738453507; E-mail: ashraful.haque@qimr.edu.au
View this article at: http://www.jci.org/articles/view/70698
Journal
Journal of Clinical Investigation