We have just released a new paper from our lab arising from Vicky Miller’s work.
In this paper we show that artificially juxtaposing the ER and mitochondrial membranes is sufficient to drive fragmentation of the mitochondria. Vicky used the rapamycin-dependent knock-sideways system developed by Scottie Robinson in Cambridge to achieve this. Using an engineered ER-localized transmembrane domain tethered to FKBP and a mitochondrially targeted FRB domain she was able to induce close apposition of the two membranes in a rapamycin dependent manner. Two things were immediately evident on doing this – first that there is a rapid sequestration of the mito-YFP-FRB into puncta that presumably represent a sub-domain of the mitochondrial membrane and second, over the course of the next 5-30 minutes, fission of mitochondria was evident. This was shown using fluorescence recovery after photobleaching to show that these fragments were indeed independent of one another. Vicky also showed that these fragments retained their mitochondrial membrane potential.
Our work shows that this artificial “knocking” of the ER to the mitochondria is sufficient to drive fission. We have not explored this phenomenon in further detail as it lies considerably outside of our area of expertise. However, we do believe that this engineered system might have some use in dissecting the mechanisms that control ER-mitochondrial contacts and the consequences of this. Consequently, we have made this work available as a preprint on BiorXiv and have also submitted it for peer review. Constructs will be freely available and when we get the chance we will deposit them with Addgene.
The full PDF is available on BiorXiv here: http://www.biorxiv.org/content/early/2014/05/28/005645
Miller, V.J. and Stephens, D.J. (2014) Artificially inducing close apposition of endoplasmic reticulum and mitochondria induces mitochondrial fragmentation. BiorXiv dx.doi.org/10.1101/005645