Published online
doi:10.1083/jcb.200809060
The Journal of Cell Biology, Vol. 184, No. 5, 707-719
The Rockefeller University Press, 0021-9525 $30.00
© Berman et al.
Bcl-xL increases mitochondrial fission, fusion, and biomass in neurons
Sarah B. Berman1,3,5,
Ying-bei Chen4,
Bing Qi1,
J. Michael McCaffery6,
Edmund B. Rucker, III7,
Sandra Goebbels8,
Klaus-Armin Nave8,
Beth A. Arnold5,
Elizabeth A. Jonas9,
Fernando J. Pineda1,2, and
J. Marie Hardwick1,3,4
1 W. Harry Feinstone Department of Molecular Microbiology and Immunology, and 2 Department of Biostatistics, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205
3 Department of Neurology and 4 Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine, Baltimore, MD 21205
5 Department of Neurology, Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA 15260
6 Department of Biology, and the Integrated Imaging Center, Johns Hopkins University, Baltimore, MD 21218
7 Animal Sciences Unit, University of Missouri, Columbia, MO 65211
8 Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, D-37075 Goettingen, Germany
9 Department of Internal Medicine, Yale University, New Haven, CT 06520
Correspondence to J. Marie Hardwick: hardwick{at}jhu.edu
Mitochondrial fission and fusion are linked to synaptic activity in healthy neurons and are implicated in the regulation of apoptotic cell death in many cell types. We developed fluorescence microscopy and computational strategies to directly measure mitochondrial fission and fusion frequencies and their effects on mitochondrial morphology in cultured neurons. We found that the rate of fission exceeds the rate of fusion in healthy neuronal processes, and, therefore, the fission/fusion ratio alone is insufficient to explain mitochondrial morphology at steady state. This imbalance between fission and fusion is compensated by growth of mitochondrial organelles. Bcl-xL increases the rates of both fusion and fission, but more important for explaining the longer organelle morphology induced by Bcl-xL is its ability to increase mitochondrial biomass. Deficits in these Bcl-xL–dependent mechanisms may be critical in neuronal dysfunction during the earliest phases of neurodegeneration, long before commitment to cell death.
Abbreviations used in this paper: cKO, conditional knockout; DIV, days in vitro; dn, dominant negative; DrOF, direct observation of fission/fusion; E, embryonic day; mtPA-GFP, mitochondria-targeted photoactivatable-GFP; mtRFP, mitochondria-targeted red fluorescent protein; VDAC, voltage-dependent anion channel.
© 2009 Berman et al.
This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.jcb.org/misc/terms.shtml). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).

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