Abstract
TFEB promotes lysosomal biogenesis, autophagy, and lysosomal exocytosis. The present study characterized the consequence of inducible TFEB overexpression in cardiomyocytes in vivo. We generated cardiomyocyte-specific doxycycline inducible (Tet off) mice to achieve spatial and temporal control of TFEB overexpression, by crossing TFEB transgenic mice with mice harboring the tTA transgene (TFEB/tTA). Two weeks after doxycycline removal, an 8-fold increase in TFEB protein expression was observed in transgenic hearts. Heart weight normalized to tibia length was increased by 2.5-fold following TFEB overexpression (TFEB/tTA), characterized by induction of markers of pathological hypertrophy, such as Nppa, Nppb and Acta1, progressive contractile dysfunction and cardiac dilatation. Overexpression of TFEB resulted in premature death, associated with high degree AV block. Reversal of TFEB overexpression normalized cardiac structure and function. Mitochondrial respiration and ATP levels were preserved after 2-weeks of TFEB induction, despite reduced mitochondrial (OXPHOS) protein expression, mtDNA content, and altered mitochondrial morphology. Signaling through mTOR was induced in TFEB/tTA mice, and when inhibited by rapamycin treatment for 4 weeks, partially offset left ventricular dysfunction. Transcriptome analysis revealed early suppression of mitochondrial metabolic pathways, induction of fibrosis and altered calcium signaling. MCOLN1, a lysosomal calcium release channel, the calcineurin target RCAN1.4, and the mitochondrial calcium uniporter (MCU) were strikingly induced in TFEB/tTA mice. In summary, persistent overexpression of TFEB at high levels (8-fold protein upregulation) in cardiomyocytes promotes pathologic cardiac hypertrophy via suppression of mitochondrial bioenergetic pathways and activation of pro-fibrotic and calcium regulatory pathways.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Correct spelling for the corresponding author
Abbreviations
- AAV
- Adeno-associated viruses
- α-MHC
- alpha- myosin heavy chain
- CMV
- Cytomegalovirus
- CQ
- Chloroquine
- DMSO
- dimethyl sulfoxide
- DTNB 5
- 5-dithio-bis-(2-nitrobenzoic acid
- E-C
- coupling Excitation-Contraction coupling
- EDV
- End-Diastolic Volume
- EF
- Ejection Fraction
- EKG
- electrocardiogram
- ER
- Endoplasmic Reticulum
- ESV
- End-Systolic Volume
- HFrRF
- Heart Failure reduced Ejection Fraction
- LC3B
- Microtubule-associated protein light chain
- LV
- Left ventricle
- MAPK1
- Mitogen-activated protein kinase 1
- MCOLN1
- Mucolipin 1
- MCU
- mitochondrial calcium uniporter
- MFN
- Mitofusin
- Mit/TFE
- microphthalmia/transcription factor E
- NADP+
- nicotinamide adenine dinucleotide phosphate
- OPA1
- Optic atrophy 1
- PFA
- paraformaldehyde
- PGC1α
- Peroxisome proliferator activated receptor-γ coactivator 1α
- PVDF
- Polyvinylidene fluoride or polyvinylidene difluoride
- RIPA
- Radioimmunoprecipitation assay buffer
- SR
- Sarcoplasmic reticulum
- STED
- Stimulated emission depletion
- TAC
- Transaortic constriction
- TetO
- Tetracycline Operator
- TFEB
- Transcription factor EB
- TRE
- Tetracycline response element
- tTA
- Tetracycline
- tTA
- tetracycline-controlled transactivator protein
- UPR
- unfolded protein response
- WGA
- Wheat Germ Agglutinin