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Long OPA1 isoforms mediate a membrane potential‐dependent threshold for mitochondrial fusion in AC16 cardiomyocytes
Author(s) -
Gilkerson Robert,
Maynard Kristen,
De La Torre Patrick,
Keniry Megan
Publication year - 2020
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.2020.34.s1.04672
Subject(s) - mitochondrial fusion , microbiology and biotechnology , atp–adp translocase , mitochondrion , inner mitochondrial membrane , lipid bilayer fusion , translocase of the outer membrane , biology , gene isoform , chemistry , biochemistry , mitochondrial dna , membrane , gene
The bioenergetic function of mitochondria is linked to its organellar structural dynamics by optic atrophy‐1 (OPA1), a nuclear‐encoded protein that mediates fusion of the mitochondrial inner membrane. OPA1‐mediated inner membrane fusion is dependent on the transmembrane potential across the mitochondrial inner membrane (Δψ m ): long (L‐OPA1) isoforms accomplish fusion for an interconnected reticular morphology when Δψ m is intact. Upon loss of Δψ m , L‐OPA1 is cleaved by the OMA1 metalloprotease, causing accumulation of short S‐OPA1 and collapse of mitochondrial fusion to a fragmented morphology. We examined Δψ m ‐sensitive mitochondrial fusion in human AC16 cardiomyocytes treated with carbonyl cyanide m‐chlorophenyl hydrazone (CCCP), an uncoupler of Δψ m . Upon increasing titration with CCCP, mitochondrial fusion collapses at [CCCP] > 2 μM, as determined using blinded ImageJ quantification of mitochondrial morphology. Similarly, OPA1 Western blotting revealed that AC16s show a significant loss of fusion‐active L‐OPA1 at [CCCP] > 2 μM. Taken together, these findings indicate that L‐OPA1 maintains mitochondrial fusion, but that OMA1 is activated at [CCCP] > 2 μM, causing L‐OPA1 cleavage and collapse of mitochondrial fusion. Experiments in progress are examining OMA1 activation at this Δψ m breakpoint, as well as impact of altered OPA1 and OMA1 expression. Support or Funding Information NIGMS 5SC3GM116669 (to R.G.) NIGMS 1SC3GM132053 (to M.K.) UTRGV Presidential Graduate Research Assistantship (to P. D.)