Mitochondria modulate Ca 2+ signals by taking up, buffering, and releasing Ca 2+ at key
locations near Ca 2+ release or influx channels. The role of such local interactions between
channels and organelles is difficult to establish in living cells because mitochondria form an
interconnected network constantly remodeled by coordinated fusion and fission reactions.
To study the effect of a controlled disruption of the mitochondrial network on Ca 2+
homeostasis, we took advantage of hFis1, a protein that promotes mitochondrial fission by …