Electrical coupling and plasticity of the mitochondrial network

F. De Giorgi, L. Lartigue, F. Ichas
Cell Calcium. 2000-11-01; 28(5-6): 365-370
DOI: 10.1054/ceca.2000.0177

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Kinetic fluorescence imaging and the potentiometric probe tetramethylrhodamine
methyl ester (TMRM) were used to evoke and detect changes in membrane potential
(delta Psi(m)) of individual mitochondria in living cells. As a combined effect
of preferential TMRM accumulation in mitochondria, and of TMRM photoactivation,
individual organelles displayed sharp transient depolarizations caused by local
reactive oxygen species (ROS)-mediated gatings of the mitochondrial permeability
transition pore (PTP). In COS-7 cells, such directed repetitive gatings of the
PTP gave rise to stochastic delta Psi(m)flickering at the level of individual
organelles, but also to prominent synchronous delta Psi(m)transitions in whole
subgroups of the mitochondrial population, indicative of the existence of an
underlying electrically coupled mitochondrial network. In single cells, this
network could comprise as much as 65% of the total mitochondrial population, a nd
exhibited a high plasticity with mitochondrial units spontaneously connecting to
and disconnecting from the coupled structure within seconds. These results
indicate that in resting cells, the mitochondrial network is a dynamic
proton-conducting structure capable to commute and coordinate electrical signals
generated by the PTP.


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