Miro proteins coordinate microtubule‐ and actin‐dependent mitochondrial transport and distribution

Abstract

In the current model of mitochondrial trafficking, Miro1 and Miro2 Rho‐GTPases regulate mitochondrial transport along microtubules by linking mitochondria to kinesin and dynein motors. By generating Miro1/2 double‐knockout mouse embryos and single‐ and double‐knockout embryonic fibroblasts, we demonstrate the essential and non‐redundant roles of Miro proteins for embryonic development and subcellular mitochondrial distribution. Unexpectedly, the TRAK1 and TRAK2 motor protein adaptors can still localise to the outer mitochondrial membrane to drive anterograde mitochondrial motility in Miro1/2 double‐knockout cells. In contrast, we show that TRAK2‐mediated retrograde mitochondrial transport is Miro1‐dependent. Interestingly, we find that Miro is critical for recruiting and stabilising the mitochondrial myosin Myo19 on the mitochondria for coupling mitochondria to the actin cytoskeleton. Moreover, Miro depletion during PINK1/Parkin‐dependent mitophagy can also drive a loss of mitochondrial Myo19 upon mitochondrial damage. Finally, aberrant positioning of mitochondria in Miro1/2 double‐knockout cells leads to disruption of correct mitochondrial segregation during mitosis. Thus, Miro proteins can fine‐tune actin‐ and tubulin‐dependent mitochondrial motility and positioning, to regulate key cellular functions such as cell proliferation.

Peroxisomal fission is modulated by the mitochondrial Rho‐GTPases, Miro1 and Miro2

“…Miro has been extensively documented to be critical for mitochondrial distribution through bidirectional microtubule-dependent trafficking in a wide variety of species and cell types [31,[41][42][43][44]. Miro has been extensively documented to be critical for mitochondrial distribution through bidirectional microtubule-dependent trafficking in a wide variety of species and cell types [31,[41][42][43][44].…”

“…To quantify whether Miro is also required to establish peroxisomal distribution, a Sholl-based quantification method was applied [30,31]. Organelle distribution was then measured by concentric circles being drawn from the centre of the cell at 1-lm intervals and the inter-circle organelle marker signal being quantified, and plotted with distance ( Fig EV3A) [31]. Organelle distribution was then measured by concentric circles being drawn from the centre of the cell at 1-lm intervals and the inter-circle organelle marker signal being quantified, and plotted with distance ( Fig EV3A) [31].…”

“…The mitochondrial Rho-GTPases, Miro1 and Miro2, are outer mitochondrial membrane (OMM) proteins critical for mitochondrial trafficking [27][28][29][30][31]. Taking advantage of Miro knockout mouse embryonic fibroblasts (MEFs), we find that in contrast to previous reports, and its role at mitochondria, Miro is not required to establish steady-state peroxisomal distribution through long-range microtubule-dependent trafficking [26,31,34]. Here, we confirm that Miro1 and Miro2 are not strictly localised to mitochondria but are also localised Neuroscience, Physiology and Pharmacology Department, University College London, London, UK *Corresponding author.…”

Mitochondrial-cytoskeletal interactions: dynamic associations that facilitate network function and remodeling

“…Since its initial discovery, Myo19 has been implicated in a range of functions, including targeting mitochondria to stress induced filopodia [38,39] and coordinating mitochondrial inheritance upon cytokinesis [40]. Most recently, Myo19 localization to mitochondria was shown to be dependent on Miro proteins, suggesting that Miro may regulate both actin and microtubule based mitochondrial motility [41]. In addition to Myo19, there is evidence that other myosin motors facilitate mitochondria dynamics.…”

Miro1 – the missing link to peroxisome motility

“…Instead, Covill-Cooke and colleagues observed a decrease in peroxisome oscillatory movement. This type of short-range motility accounts for 85–95% of peroxisome movements in the cell, and although poorly characterized, might rely on diffusive behaviour and interactions with the actin cytoskeleton [27,28]. Although conflicting with the expression and silencing results, it is possible that in the absence of Miro1, other motor complexes enable fast and directed motility of peroxisomes, but also that Miro1 plays additional roles in peroxisome motility.…”