Thursday, 10 July 2014

stationary energy stores are not good

Ohno N, Chiang H, Mahad DJ, Kidd GJ, Liu L, Ransohoff RM, Sheng ZH, Komuro H, Trapp BD. Mitochondrial immobilization mediated by syntaphilin facilitates survival of demyelinated axons. Proc Natl Acad Sci U S A. 2014. pii: 201401155. [Epub ahead of print]


Axonal degeneration is a primary cause of permanent neurological disability in individuals with the CNS demyelinating disease multiple sclerosis. Dysfunction of axonal mitochondria and imbalanced energy demand and supply are implicated in degeneration of chronically demyelinated axons. The purpose of this study was to define the roles of mitochondrial volume and distribution in axonal degeneration following acute CNS demyelination. We show that the axonal mitochondrial volume increase following acute demyelination of WT CNS axons does not occur in demyelinated axons deficient in syntaphilin, an axonal molecule that immobilizes stationary mitochondria to microtubules. These findings were supported by time-lapse imaging of WT and syntaphilin-deficient axons in vitro. When demyelinated, axons deficient in syntaphilin degenerate at a significantly greater rate than WT axons, and this degeneration can be rescued by reducing axonal electrical activity with the Na+ channel blocker flecainide. These results support the concept that syntaphilin-mediated immobilization of mitochondria to microtubules is required for the volume increase of axonal mitochondria following acute demyelination and protects against axonal degeneration in the CNS.


Mitochondria the energy producing units of a cell are ferried back and forth along neuronal axons by the scaffolding of the cell (microtubule) such they can make energy where it is needed. A molecule called syntaphin is a molecular clamp if it is not present this is associated with more nerve damage

3 comments:

  1. MD, is this the type of mechanism that would be behind any action of phenytoin?

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    Replies
    1. Phenytoin acts by blocking sodium channels which are upregulated in demyelinated nerves and increase energy requirements from mitochondria so any effect on mitochondria will be indirect.

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  2. Not really. Phenytoin acts as a blocker of sodium channels which are upregulated on demyelinated nerves and which put an extra burden on the energy reserves of the nerve and thus puts more strain on mitochondria. Thus phenytoin will have an indirect effect on mitochondria in reducing that energy burden rather than the mechanism described above.

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