Thursday, 19 February 2015

Trans-mitochondrial coordination of cristae at regulated membrane junctions

Martin Picard, Meagan J. McManus, György Csordás et al.

The existence of junctions which electrically couple adjacent mitochondria through their outer mitochondrial membranes, called inter-mitochondrial junctions (IMJs), has been known for almost three decades.  IMJs do not necessarily form when mitochondria come into contact, and the phenomenon is distinct from mitochondrial fusion, since the inner/outer mitochondrial membranes remain distinct when an IMJ is formed. Indeed, the authors note that the presence of IMJs tend to correlate with how dependent the cell is on oxidative phosphorylation. They are dynamically regulated, and can form on addition of electron donors to generate membrane potential.

The authors investigated the influence of IMJs on cristae structure, and found that cristae align themselves perpendicularly to IMJs, and at a higher density than other regions. Even after genetic perturbations to interfere with cristae structure, the cristae continued to align with IMJs. They observed that cristae would bend a great deal, so they could participate in IMJs, which suggests biological regulation. The authors present a novel drug-inducible system which can physically tether adjacent mitochondria. They show that both cristae and IMJ formation can be induced with this system, by stable juxtaposition of mitochondria. Their data suggest that such structures exist to promote information transfer inside the cytoplasm of eukaryotic cells.

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