Quantitation of mitochondrial dynamics by photolabeling of individual organelles shows that mitochondrial fusion is blocked during the Bax activation phase of apoptosis

Mariusz Karbowski; Damien Arnoult; Hsiuchen Chen; David C Chan; Carolyn L Smith; Richard J Youle

doi:10.1083/jcb.200309082

Quantitation of mitochondrial dynamics by photolabeling of individual organelles shows that mitochondrial fusion is blocked during the Bax activation phase of apoptosis

J Cell Biol. 2004 Feb 16;164(4):493-9. doi: 10.1083/jcb.200309082. Epub 2004 Feb 9.

Authors

Mariusz Karbowski¹, Damien Arnoult, Hsiuchen Chen, David C Chan, Carolyn L Smith, Richard J Youle

Affiliation

¹ Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.

Abstract

A dynamic balance of organelle fusion and fission regulates mitochondrial morphology. During apoptosis this balance is altered, leading to an extensive fragmentation of the mitochondria. Here, we describe a novel assay of mitochondrial dynamics based on confocal imaging of cells expressing a mitochondrial matrix-targeted photoactivable green fluorescent protein that enables detection and quantification of organelle fusion in living cells. Using this assay, we visualize and quantitate mitochondrial fusion rates in healthy and apoptotic cells. During apoptosis, mitochondrial fusion is blocked independently of caspase activation. The block in mitochondrial fusion occurs within the same time range as Bax coalescence on the mitochondria and outer mitochondrial membrane permeabilization, and it may be a consequence of Bax/Bak activation during apoptosis.

Copyright The Rockefeller University Press

MeSH terms

Amino Acid Chloromethyl Ketones / metabolism
Animals
Apoptosis / physiology*
Biological Assay / methods
Caspase Inhibitors
Caspases / metabolism
Cells, Cultured
Fibroblasts / cytology
Fibroblasts / metabolism
Green Fluorescent Proteins
Humans
Luminescent Proteins / genetics
Luminescent Proteins / metabolism*
Membrane Fusion / physiology*
Mice
Microscopy, Confocal
Mitochondria / metabolism*
Mitochondrial Proteins / genetics
Mitochondrial Proteins / metabolism
Neurons / cytology
Neurons / metabolism
Proto-Oncogene Proteins / metabolism*
Proto-Oncogene Proteins c-bcl-2*
Rats
Recombinant Fusion Proteins / genetics
Recombinant Fusion Proteins / metabolism
bcl-2-Associated X Protein

Substances

Amino Acid Chloromethyl Ketones
BAX protein, human
Bax protein, mouse
Bax protein, rat
Caspase Inhibitors
Luminescent Proteins
Mitochondrial Proteins
Proto-Oncogene Proteins
Proto-Oncogene Proteins c-bcl-2
Recombinant Fusion Proteins
bcl-2-Associated X Protein
benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
Green Fluorescent Proteins
Caspases