Early ERK1/2 activation promotes DRP1-dependent mitochondrial fission necessary for cell reprogramming.

Javier Prieto,Raquel Ferrer-Lorente,Ramón Sendra,Xavier Ponsoda,Carlos López-García,Marian León,Angel Raya,Roque Bort,Josema Torres

doi:10.1038/ncomms11124

Abstract

During the process of reprogramming to induced pluripotent stem (iPS) cells, somatic cells switch from oxidative to glycolytic metabolism, a transition associated with profound mitochondrial reorganization. Neither the importance of mitochondrial remodelling for cell reprogramming, nor the molecular mechanisms controlling this process are well understood. Here, we show that an early wave of mitochondrial fragmentation occurs upon expression of reprogramming factors. Reprogramming-induced mitochondrial fission is associated with a minor decrease in mitochondrial mass but not with mitophagy. The pro-fission factor Drp1 is phosphorylated early in reprogramming, and its knockdown and inhibition impairs both mitochondrial fragmentation and generation of iPS cell colonies. Drp1 phosphorylation depends on Erk activation in early reprogramming, which occurs, at least in part, due to downregulation of the MAP kinase phosphatase Dusp6. Taken together, our data indicate that mitochondrial fission controlled by an Erk-Drp1 axis constitutes an early and necessary step in the reprogramming process to pluripotency.

Highlights

During the process of reprogramming to induced pluripotent stem cells, somatic cells switch from oxidative to glycolytic metabolism, a transition associated with profound mitochondrial reorganization
Mitochondrial morphology was assessed in mouse embryonic fibroblasts (MEFs), before or after transduction with retroviruses encoding the OSKM reprogramming factors for the indicated times, by immunofluorescence (IF) with anti-Tom[20] antibody (Fig. 1a)
During cell reprogramming, somatic cells undergo a profound reorganization in the number and shape of mitochondria that reflects the transition from a somatic oxidative- into a pluripotent glycolytic-based metabolism[39]

Summary

Introduction

During the process of reprogramming to induced pluripotent stem (iPS) cells, somatic cells switch from oxidative to glycolytic metabolism, a transition associated with profound mitochondrial reorganization. Drp[1] phosphorylation depends on Erk activation in early reprogramming, which occurs, at least in part, due to downregulation of the MAP kinase phosphatase Dusp[6]. Mitochondrial association is promoted by phosphorylation of human DRP1 at serine 616 (S616) by CDK1 during mitosis or by PKCd in neuronal cells under oxidative stress[19,20] On another hand, phosphorylation of serine 637 in human DRP1 by PKA impairs its recruitment to mitochondria, whereas dephosphorylation of this residue by PP2A or calcineurin favours its recruitment to these organelles[21,22,23]. It was shown that phosphorylation of DRP1-S616 by ERK2 promotes mitochondrial fission and mitogen-activated protein kinase (MAPK)-driven tumour growth[28,29]. The DUSP family of protein phosphatases is dedicated to the specific regulation of MAPKs in mammalian cells, with DUSP6, DUSP7 and DUSP9 being the major cytoplasmic phosphatases that dephosphorylate and inactivate ERK1/2 (refs 30,31)

Methods

Results

Conclusion