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| Subject Categories: Membranes & Transport | Cellular Metabolism |
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| The EMBO Journal
(2002) 21, 1616–1627, doi: 10.1093/emboj/21.7.1616 |
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| Mitochondria are morphologically and functionally heterogeneous within cells |
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| Tony J. Collins1, Michael J. Berridge1, Peter Lipp1 and Martin D. Bootman1, 2 |
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1 Laboratory of Molecular Signalling, The Babraham Institute, Babraham, Cambridge CB2 4AT UK 2 Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK To whom correspondence should be addressed Tony J. Collins, tony.collins@bbsrc.ac.uk Received 6 December 2001; Revised 30 January 2002; Accepted 6 February 2002. |
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| Abstract |
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| We investigated whether mitochondria represent morphologically continuous and functionally homogenous entities within single intact cells. Physical continuity of mitochondria was determined by three-dimensional reconstruction of fluorescence from mitochondrially targeted DsRed1 or calcein. The mitochondria of HeLa, PAEC, COS-7, HUVEC, hepatocytes, cortical astrocytes and neuronal cells all displayed heterogeneous distributions and were of varying sizes. There was a denser aggregation of mitochondria in perinuclear positions than in the cell periphery, where individual isolated mitochondria could be seen clearly. Using fluorescence-recovery after photobleaching, we observed that DsRed1 and calcein were highly mobile within the matrix of individual mitochondria, and that mitochondria within a cell were not lumenally continuous. Mitochondria were not electrically coupled, since only individual mitochondria were observed to depolarize following irradiation of TMRE-loaded cells. Functional heterogeneity of mitochondria in single cells was observed with respect to membrane potential, sequestration of hormonally evoked cytosolic calcium signals and timing of permeability transition pore opening in response to tert-butyl hydroperoxide. Our data indicate that mitochondria within individual cells are morphologically heterogeneous and unconnected, allowing them to have distinct functional properties. |
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| Keywords: calcium, FRAP, membrane potential, mitochondria, permeability transition |
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