Abstract
Neurons are extremely polarized structures with long axons and dendrites, which require proper distribution of mitochondria and maintenance of mitochondrial dynamics for neuronal functions and survival. Indeed, recent studies show that various neurological disorders are linked to mitochondrial transport in neurons. Mitochondrial anterograde transport is believed to deliver metabolic energy to synaptic terminals where energy demands are high, while mitochondrial retrograde transport is required to repair or remove damaged mitochondria in axons. It has been suggested that Ca2+ plays a key role in regulating mitochondrial transport by altering the configuration of mitochondrial protein, miro. However, molecular mechanisms that regulate mitochondrial transport in neurons still are not well characterized. In this review, we will discuss the roles of miro in mitochondrial transport and how the recently identified components of the mitochondrial calcium uniporter add to our current model of mitochondrial mobility regulation.
Highlights
Mitochondria are vital organelles that provide ATP, maintain Ca2+ homeostasis, and regulate apoptosis in all eukaryotic cells
To further test if Ca2+ content in mitochondrial matrix regulates mitochondrial transport, Chang et al (2011) used drugs that inhibit or activate the mitochondrial calcium uniporter (MCU) complex and investigated the mobility of mitochondria. They found that blocking MCU complex in the presence of high cytoplasmic Ca2+ preserved mitochondrial movement, suggesting that Ca2+ influx into the mitochondrial matrix plays an obligatory role for mitochondrial movement arrest (Figure 1, c)
The MCU complex contains three distinct proteins: MCU, mitochondrial calcium uptake1 (MICU1), and mitochondria calcium uniporter regulator 1 (MCUR1), which regulates the influx of calcium into the mitochondrial matrix
Summary
Mitochondria are vital organelles that provide ATP, maintain Ca2+ homeostasis, and regulate apoptosis in all eukaryotic cells. Mitochondrial transport is known to be mediated by interactions between the mitochondrial adaptor proteins to kinesin and dynein motors, as well as the binding of the motor proteins to the cytoskeleton track (Pilling et al, 2006; Russo et al, 2009; reviewed in Saxton and Hollenbeck, 2012). In spite of this widely held point of view, it still remains unclear whether internal parameters in mitochondria provide another level of regulation that increases the efficiency of mitochondrial transport in axons. It contains a single transmembrane domain on the Frontiers in Cellular Neuroscience www.frontiersin.org
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