Article

Dephosphorylation by calcineurin regulates translocation of Drp1 to mitochondria

Dulbecco-Telethon Institute, Padua, Italy.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 11/2008; 105(41):15803-8. DOI: 10.1073/pnas.0808249105
Source: PubMed

ABSTRACT Changes in mitochondrial morphology that occur during cell cycle, differentiation, and death are tightly regulated by the balance between fusion and fission processes. Excessive fragmentation can be caused by inhibition of the fusion machinery and is a common consequence of dysfunction of the organelle. Here, we show a role for calcineurin-dependent translocation of the profission dynamin related protein 1 (Drp1) to mitochondria in dysfunction-induced fragmentation. When mitochondrial depolarization is associated with sustained cytosolic Ca(2+) rise, it activates the cytosolic phosphatase calcineurin that normally interacts with Drp1. Calcineurin-dependent dephosphorylation of Drp1, and in particular of its conserved serine 637, regulates its translocation to mitochondria as substantiated by site directed mutagenesis. Thus, fragmentation of depolarized mitochondria depends on a loop involving sustained Ca(2+) rise, activation of calcineurin, and dephosphorylation of Drp1 and its translocation to the organelle.

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Available from: Luca Scorrano, Aug 24, 2015
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    • "Please cite this article in press as: Pyakurel et al., Extracellular Regulated Kinase Phosphorylates Mitofusin 1 to Control Mitochondrial Morphology and Apoptosis, Molecular Cell (2015), http://dx.doi.org/10.1016/j.molcel.2015.02.021 RESULTS MFN1 Is Phosphorylated at T562 Whether and how phosphorylation regulates mitochondrial fusion is unclear: we therefore set out to identify if MFNs are phosphorylated. Phosphorylated and non-phosphorylated Flag-tagged MFN1 or MFN2 expressed in untreated mouse embryonic fibroblasts (MEFs) were separated by affinity chromatography on a column that specifically binds phosphorylated residues (Cereghetti et al., 2008). Immunoblotting indicated that both Flag-MFN1 and MFN2 avidly bound to the column (Figure 1A). "
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    Molecular cell 03/2015; 104(2). DOI:10.1016/j.molcel.2015.02.021 · 14.46 Impact Factor
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    • "Drp1 is intimately associated with the apoptotic process (Arnoult, 2007) in which Drp1-mediated mitochondrial fragmentation augments the release of cytochrome C from mitochondria, an early step in apoptosis (Cassidy-Stone et al., 2008). As a major regulator of Drp1 activity, cAMP-dependent protein kinase (PKA) phosphorylates Drp1 and leads to its cytosolic sequestration promoting an elongated mitochondrial network (Cereghetti et al., 2008; Chang and Blackstone, 2007; Cribbs and Strack, 2007). A neuroprotective role of PKA phosphorylation of Drp1 has been suggested as constitutive Drp1 phosphorylation at the consensus PKA site inhibits cytochrome C release and apoptosis in neuronal PC12 cells (Cribbs and Strack, 2007). "
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    • "Overexpression of a mutant form of Drp1 (Drp1- K38A), which acts as a dominant negative (Smirnova et al, 1998), or using the Drp1 inhibitor mdivi-1, significantly attenuated the NMDA-mediated mitochondrial fragmentation during the first hour of NMDA treatment (Fig 2D and E). Excessive calcium uptake by mitochondria in excitotoxicity causes mitochondrial depolarization (Soriano et al, 2006b; Nicholls, 2009), this produces an increase in cytosolic calcium that can activate calcineurin which has been shown to de-phosphorylate Drp1 to promote its recruitment to mitochondria and fission (Cereghetti et al, 2008). We analyzed whether mitochondrial fission preceded or was posterior to mitochondrial depolarization. "
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    ABSTRACT: Mitochondrial fusion and fission is a dynamic process critical for the maintenance of mitochondrial function and cell viability. During excitotoxicity neuronal mitochondria are fragmented, but the mechanism underlying this process is poorly understood. Here, we show that Mfn2 is the only member of the mitochondrial fusion/fission machinery whose expression is reduced in in vitro and in vivo models of excitotoxicity. Whereas in cortical primary cultures, Drp1 recruitment to mitochondria plays a primordial role in mitochondrial fragmentation in an early phase that can be reversed once the insult has ceased, Mfn2 downregulation intervenes in a delayed mitochondrial fragmentation phase that progresses even when the insult has ceased. Downregulation of Mfn2 causes mitochondrial dysfunction, altered calcium homeostasis, and enhanced Bax translocation to mitochondria, resulting in delayed neuronal death. We found that transcription factor MEF2 regulates basal Mfn2 expression in neurons and that excitotoxicity-dependent degradation of MEF2 causes Mfn2 downregulation. Thus, Mfn2 reduction is a late event in excitotoxicity and its targeting may help to reduce excitotoxic damage and increase the currently short therapeutic window in stroke.
    The EMBO Journal 08/2014; 33(20). DOI:10.15252/embj.201488327 · 10.75 Impact Factor
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