Proteasome functional insufficiency activates the calcineurin-NFAT pathway in cardiomyocytes and promotes maladaptive remodelling of stressed mouse hearts.
OBJECTIVE
Proteasome functional insufficiency (PFI) may play an important role in the progression of congestive heart failure but the underlying molecular mechanism is poorly understood. Calcineurin and nuclear factor of activated T-cells (NFAT) are degraded by the proteasome, and the calcineurin-NFAT pathway mediates cardiac remodelling. The present study examined the hypothesis that PFI activates the calcineurin-NFAT pathway and promotes maladaptive remodelling of the heart.


RESULTS
Using a reporter gene assay, we found that pharmacological inhibition of 20S proteasomes stimulated NFAT transactivation in both mouse hearts and cultured adult mouse cardiomyocytes. Proteasome inhibition stimulated NFAT nuclear translocation in a calcineurin-dependent manner and led to a maladaptive cell shape change in cultured neonatal rat ventricular myocytes. Proteasome inhibition facilitated left ventricular dilatation and functional decompensation and increased fatality in mice with aortic constriction while causing cardiac hypertrophy in the sham surgery group. It was further revealed that both calcineurin protein levels and NFAT transactivation were markedly increased in the mouse hearts with desmin-related cardiomyopathy and severe PFI. Expression of an aggregation-prone mutant desmin also directly increased calcineurin protein levels in cultured cardiomyocytes.


CONCLUSIONS
The calcineurin-NFAT pathway in the heart can be activated by proteasome inhibition and is activated in the heart of a mouse model of desmin-related cardiomyopathy that is characterized by severe PFI. The interplay between PFI and the calcineurin-NFAT pathway may contribute to the pathological remodelling of cardiomyocytes characteristic of congestive heart failure.
Tang
Mingxin
M
Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, 414 East Clark Street, Lee Medical Building, Vermillion, SD 57069, USA.
Li
Jie
J
Huang
Wei
W
Su
Huabo
H
Liang
Qiangrong
Q
Tian
Zongwen
Z
Horak
Kathleen M
KM
Molkentin
Jeffery D
JD
Wang
Xuejun
X
D000818:Animals; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D019703:Calcineurin / Q000502:physiology*; D002478:Cells, Cultured; D003893:Desmin / Q000235:genetics; D006333:Heart Failure / Q000473:pathology / Q000503:physiopathology*; D051379:Mice; D008822:Mice, Transgenic; D023421:Models, Animal; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D050778:NFATC Transcription Factors / Q000235:genetics / Q000502:physiology*; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000502:physiology*; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D013312:Stress, Physiological / Q000502:physiology*
D001897:Boronic Acids; D003893:Desmin; C423917:MG 262; D050778:NFATC Transcription Factors; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011719:Pyrazines; D000069286:Bortezomib; D019703:Calcineurin; D046988:Proteasome Endopeptidase Complex