Premium
Overexpression of Muscle Ring Finger 1 Reduces Mitochondrial Volume in Cardiomyocytes
Author(s) -
Parikh Chirag,
Kobayashi Satoru,
Gerdes Martin,
Willis Monte S,
Liang Qiangrong
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.1015.3
Subject(s) - mitophagy , mitochondrion , propidium iodide , microbiology and biotechnology , mitochondrial fission , viability assay , biology , myocyte , mitochondrial fusion , cell , chemistry , mitochondrial dna , apoptosis , programmed cell death , biochemistry , autophagy , gene
Objectives Muscle Ring Finger 1 (MuRF1) is an ubiquitin E3 ligase that participates in atrophy of cardiac myocytes, and when upregulated, increases risk of dilated cardiomyopathy. While many studies have shown the regressive atrophy that MuRF1 participates in, more recent studies also indicate that increased expression of MuRF1 results in broad disruption of metabolic functions in cardiac tissues and in particular, mitochondria. However, it is unclear what role MuRF1 plays with mitochondrial regulation. Since the energy requirement in cardiac muscle cells is high, mitochondrial homeostasis is tightly regulated by multiple processes which include fusion, fission, mitophagy and biogenesis. This study aimed to determine whether MuRF1 plays a role in regulation of these processes by examining the morphological changes of mitochondria and their relationship with cell viability. Methods H9C2 Cardiomyoblast cell line was pretreated with an adenovirus‐encoded mitochondrial‐targeting protein, mtRosella, a construct that results in fluorescence of mitochondria, allowing examination of morphology and mitophagy. Following this, these cells were infected with an adenovirus encoding MuRF1 to increase the protein expression levels of MuRF1. Change in MT morphology was determined with confocal microscopy. Morphological descriptors (count, average size, major and minor axes) were measured using ImageJ analysis software to describe changes in the degree of mitochondria size, fragmentation, and mitophagy. Additionally, propidium iodide staining was used in an identical setup to determine if MuRF1 overexpression affects cell viability. Results Morphometric analysis demonstrated that overexpression of MuRF1 in H9C2 cells did not change the count of mitochondria, but decreased the size of mitochondria. Both major and minor axes were decreased in the overexpression group. In addition, mitophagy levels did not differ in the overexpression group versus the control. Finally, propidium iodide staining did not show an increase in cell death in the overexpression group, a finding that agrees with other study findings. Further study is needed to determine if MuRF1 affects mitochondrial biogenesis to reduce the mitochondrial size. Conclusion Overexpression of MuRF1 is sufficient to reduce mitochondrial size but it does not have an effect on mitochondrial number and mitophagy. The reduced mitochondrial size may reduce the overall capacity of mitochondrial metabolic function and increase the sensitivity of the cardiomyocyte or the heart to pathological stresses such as ischemia and chemotherapy. Support or Funding Information NIH Grant 1R15HL120027‐01A1