Making Memories With Mitochondrial Flashes

Mitochondrial flashes in the brain help convert short-term memories into long-term ones.

AsianScientist (July 10, 2017) – A burst of activity from the mitochondria can transform a short-term memory into a long-term one. These findings, by researchers at Peking University, have been published in Nature Communications.

Synaptic plasticity is regarded as the cellular basis of learning and memory. Induced by different patterns of neuronal activities, short-term synaptic plasticity lasts for a few seconds to a few minutes, whereas long-term plasticity lasts for tens of minutes to hours.

Mitochondrial flashes or ‘mitoflashes’ are short bursts of activity from the mitochondria that include membrane depolarization, reactive oxygen species (ROS) production and matrix alkalization. First identified by Professor Cheng Heping, mitoflashes are highly conserved and have been found to exist in functional mitochondria of all cell types examined to date.

Noting that mitochondrial dysfunction has been linked to defective synaptic plasticity, Cheng and his team hypothesized that mitoflashes might be involved in the signaling transduction of synaptic plasticity. To test their hypothesis, the researchers studied the role of mitoflashes in learning and memory using rat hippocampal neurons.

Using a newly developed set of techniques including long-term continuous mitoflash imaging and photon-activation of individual mitoflash events by femtosecond laser pulsers, the team found that long-term potentiation (LTP) was always accompanied by one or more mitoflashes in nearby dendritic mitochondria. Furthermore, artificially-induced mitoflashes were able facilitate the transition from short-term synaptic potentiation to LTP.

The regulatory effect of mitoflashes on synaptic plasticity was only effective within the critical time-window of 30 minutes and a spatial extent of about 2 μm, demonstrating the spatiotemporal precision of this regulatory mechanism. Further study revealed that synaptic calcium and calcium-calmodulin kinase were important for eliciting mitoflash, which in turn released ROS to signal long-term synaptic plasticity.

This study identifies mitoflashes as digital bio-signals that play essential roles in synaptic plasticity. It reveals for the first time the bi-directional interaction between dendritic mitochondria and synapses, and provides novel insight into the biological relevance of mitoflashes. The local and transient ROS burst may provide a subcellular mechanism for ‘burning’ short-term synaptic changes into long-term memory.

The article can be found at: Fu et al. (2017) Dendritic Mitoflash as a Putative Signal for Stabilizing Long-term Synaptic Plasticity.


Source: Peking University.
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