Published online August 20, 2007
doi:10.1083/jcb.200704110
The Journal of Cell Biology, Vol. 178, No. 5, 749-755
The Rockefeller University Press, 0021-9525 $30.00
© 2007 Song et al.
OPA1 processing controls mitochondrial fusion and is regulated by mRNA splicing, membrane potential, and Yme1L
Zhiyin Song1,
Hsiuchen Chen1,
Maja Fiket2,
Christiane Alexander2, and
David C. Chan1
1 Division of Biology, California Institute of Technology, Pasadena, CA 91125
2 Department of Neuroscience, Max Delbrück Center for Molecular Medicine, 13092 Berlin, Germany
Correspondence to David C. Chan: dchan{at}caltech.edu
OPA1, a dynamin-related guanosine triphosphatase mutated in dominant optic atrophy, is required for the fusion of mitochondria. Proteolytic cleavage by the mitochondrial processing peptidase generates long isoforms from eight messenger RNA (mRNA) splice forms, whereas further cleavages at protease sites S1 and S2 generate short forms. Using OPA1-null cells, we developed a cellular system to study how individual OPA1 splice forms function in mitochondrial fusion. Only mRNA splice forms that generate a long isoform in addition to one or more short isoforms support substantial mitochondrial fusion activity. On their own, long and short OPA1 isoforms have little activity, but, when coexpressed, they functionally complement each other. Loss of mitochondrial membrane potential destabilizes the long isoforms and enhances the cleavage of OPA1 at S1 but not S2. Cleavage at S2 is regulated by the i-AAA protease Yme1L. Our results suggest that mammalian cells have multiple pathways to control mitochondrial fusion through regulation of the spectrum of OPA1 isoforms.
Abbreviations used in this paper: CCCP, carbonyl cyanide m-chlorophenyl hydrazone; MEF, mouse embryonic fibroblast; MPP, mitochondrial processing peptidase; PARL, presenilin-associated rhomboid-like; PEG, polyethylene glycol; shRNA, short hairpin RNA.

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