Direct regulation of complex I by mitochondrial MEF2D is disrupted in a mouse model of Parkinson disease and in human patients
Hua She, … , Claudia Testa, Zixu Mao
Hua She, … , Claudia Testa, Zixu Mao
Published February 14, 2011
Citation Information: J Clin Invest. 2011;121(3):930-940. https://doi.org/10.1172/JCI43871.
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Research Article Neuroscience

Direct regulation of complex I by mitochondrial MEF2D is disrupted in a mouse model of Parkinson disease and in human patients

Abstract

The transcription factors in the myocyte enhancer factor 2 (MEF2) family play important roles in cell survival by regulating nuclear gene expression. Here, we report that MEF2D is present in rodent neuronal mitochondria, where it can regulate the expression of a gene encoded within mitochondrial DNA (mtDNA). Immunocytochemical, immunoelectron microscopic, and biochemical analyses of rodent neuronal cells showed that a portion of MEF2D was targeted to mitochondria via an N-terminal motif and the chaperone protein mitochondrial heat shock protein 70 (mtHsp70). MEF2D bound to a MEF2 consensus site in the region of the mtDNA that contained the gene NADH dehydrogenase 6 (ND6), which encodes an essential component of the complex I enzyme of the oxidative phosphorylation system; MEF2D binding induced ND6 transcription. Blocking MEF2D function specifically in mitochondria decreased complex I activity, increased cellular H2O2 level, reduced ATP production, and sensitized neurons to stress-induced death. Toxins known to affect complex I preferentially disrupted MEF2D function in a mouse model of Parkinson disease (PD). In addition, mitochondrial MEF2D and ND6 levels were decreased in postmortem brain samples of patients with PD compared with age-matched controls. Thus, direct regulation of complex I by mitochondrial MEF2D underlies its neuroprotective effects, and dysregulation of this pathway may contribute to PD.

Authors

Hua She, Qian Yang, Kennie Shepherd, Yoland Smith, Gary Miller, Claudia Testa, Zixu Mao

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Figure 4

Regulation of mitochondrial gene ND6 by mitochondrial MEF2D.

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Regulation of mitochondrial gene ND6 by mitochondrial MEF2D. (A) Mt2...
(A) Mt2D and Mt2Ddn, which lacks the transactivation domain (TAD). Mito, mitochondrial targeting sequence; MADS, minichromosome maintenance 1, agamous, deficiens, and serum response factor domain. (B) Effects of Mt2D and Mt2Ddn on binding of full-length MEF2D to ND6 gene in mitochondria of SN4741 cells, revealed by ChIP assay (n = 4; **P < 0.01). Control indicates the control vector group. (C) Effects of Mt2D or Mt2Ddn on ND6 expression in SN4741 cells. Overexpression of Mt2Ddn in SN4741 cells reduced ND6, but not PPAR-γ coactivator 1 (PGC1), expression (n = 4; **P < 0.01). Control indicates the control vector group. (D) Effects of overexpression of Mt2D or Mt2Ddn on mRNA levels of mitochondria encoded genes. Real-time PCR results showed specific reduction of ND6 mRNA level by overexpression of Mt2Ddn in SN4741 cells (n = 4; **P < 0.01). Control indicates the control vector group. (E) Effects of Mt2D or Mt2Ddn on mtDNA L-strand transcription initiation in vitro (n = 3; **P < 0.01). A human mtDNA fragment containing mitochondrial L-strand promoter (LSP) and ND6 gene was used in the in vitro transcription assay. Blot shows 32P-UTP–labeled transcripts. (F) Effects of Mt2D or Mt2Ddn on mtDNA de novo transcription in vivo (n = 3; **P < 0.01). Control(-) is without primers. Control(+) indicates the control vector group.