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Myocardin Regulated Genetic Pathway Modulates Mitochondrial Permeability Transition Pore Closure to Prevent Cell Death during Cardiac Differentiation
Author(s) -
Mughal Wajihah,
Silva Rosa Simone,
Chapman Donald,
Hai Yan,
DiehlJones William,
Gordon Joseph
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.647.6
Subject(s) - myocardin , microbiology and biotechnology , mitochondrial permeability transition pore , biology , gene knockdown , mitochondrion , programmed cell death , serum response factor , transcription factor , biochemistry , apoptosis , gene
Myocardin is a transcriptional co‐activator required for cardiovascular development and cardiomyocyte differentiation. Recent studies have shown that genetic inhibition of myocardin results in congenital heart defects associated with increased programmed cell death (PCD). In addition to its established role in regulating PCD, the mitochondrial permeability transition pore (PTP) has been implicated in cardiac calcium homeostasis and myocyte maturation during development. Utilizing fluorescent staining and biochemical assays, we demonstrate that myocardin, a modulator of cardiac gene function, regulates mitochondrial PTP closure during myocyte differentiation to oppose pathways of PCD induced by protein kinase‐A (PKA) activating agents. We show that a loss of myocardin function reduces microRNA‐133a (miR‐133a) mRNA levels and induces mitochondrial dysfunction by PTP opening and reducing mitochondrial membrane potential. Furthermore, myocardin knockdown increased mitochondrial oxidative stress and mitochondrial calcium uptake in differentiated myocytes. Conversely, restoring myocardin expression rescued mitochondrial function, concurrent with a decreased expression of a mitochondrial death protein, Nix. Furthermore, miR‐133a protects against PKA‐activating agents while inhibitory molecules opposing miR‐133a increase Nix expression. With the use of genetically encoded and organelle targeted calcium sensors, our data demonstrates that miR‐133a reverses endoplasmic reticulum calcium release and prevents mitochondrial calcium uptake, in a manner dependent on Nix repression. Finally, we provide mechanistic evidence that myocardin‐dependent miR‐133a expression is regulated by histone deactylase‐5 (HDAC5) and the PKA‐regulated salt inducible kinase‐1 (SIK1). These findings support the notion that myocardin opposes PCD through mitochondrial permeability transition by regulating calcium homeostasis; however, this genetic pathway may be attenuated by pathological PKA signaling. Support or Funding Information Supported by Children's Hospital Foundation of Manitoba, Research Manitoba and NSERC Canada.