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Mitochondrial fusion is increased by the nuclear coactivator PGC-1beta.

Liesa M, Borda-d'Agua B, Medina-Gómez G, Lelliott CJ, Paz JC, Rojo M, Palacín M, Vidal-Puig A, Zorzano A - PLoS ONE (2008)

Bottom Line: Here, we demonstrate that reduced mitochondrial size observed in knock-out mice for the transcriptional regulator PGC-1beta is associated with a selective reduction in Mitofusin 2 (Mfn2) expression, a mitochondrial fusion protein.This PGC-1beta-induced elongation specifically requires Mfn2 as this process is absent in Mfn2-ablated cells.Finally, we show that PGC-1beta increases Mfn2 promoter activity and transcription by coactivating the nuclear receptor Estrogen Related Receptor alpha (ERRalpha).

View Article: PubMed Central - PubMed

Affiliation: Institute for Research in Biomedicine (IRB Barcelona), Barcelona, Spain.

ABSTRACT

Background: There is no evidence to date on whether transcriptional regulators are able to shift the balance between mitochondrial fusion and fission events through selective control of gene expression.

Methodology/principal findings: Here, we demonstrate that reduced mitochondrial size observed in knock-out mice for the transcriptional regulator PGC-1beta is associated with a selective reduction in Mitofusin 2 (Mfn2) expression, a mitochondrial fusion protein. This decrease in Mfn2 is specific since expression of the remaining components of mitochondrial fusion and fission machinery were not affected. Furthermore, PGC-1beta increases mitochondrial fusion and elongates mitochondrial tubules. This PGC-1beta-induced elongation specifically requires Mfn2 as this process is absent in Mfn2-ablated cells. Finally, we show that PGC-1beta increases Mfn2 promoter activity and transcription by coactivating the nuclear receptor Estrogen Related Receptor alpha (ERRalpha).

Conclusions/significance: Taken together, our data reveal a novel mechanism by which mammalian cells control mitochondrial fusion. In addition, we describe a novel role of PGC-1beta in mitochondrial physiology, namely the control of mitochondrial fusion mainly through Mfn2.

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Related in: MedlinePlus

Mfn2 is required for PGC-1β changes in mitochondrial morphology.(A) Representative immunocytochemistry images (performed as in Fig. 3B) from one of three independent cotransfection experiments with an empty vector (Control) or PGC-1β- encoding vector (PGC-1β) and GFP (ratio GFP:PGC-1β 1:10) of wild-type mouse embryonic fibroblasts (MEFs). Transfected cells were visualized by GFP fluorescence (data not shown). Scale bar, 10 µm. (B) Wild type mouse embryonic fibroblasts (MEF) quantification and classification attending to mitochondrial tubule length (50-75 transfected cells counted per independent experiment). Wild type MEFs with a mean mitochondrial tubule length <4 µm were considered “Short” and >4 µm were considered “Long”. “Perinuclear” MEFs displayed most mitochondria surrounding the nucleus (see Figure S4) and almost no “Fragmented” cells (with tiny spherical mitochondria, see Figure S4) were observed in transfected wild type MEFs. Results are mean±SEM and expressed as percentage of total transfected wild type MEFs counted from three independent cotransfection experiments with an empty vector (white bars) or PGC-1β (black bars) with GFP (empty vector/PGC-1β : GFP ratio 10:1). Transfected cells were observed by GFP fluorescence (data not shown). *, statistical difference at p<0.02. (C) Representative immunocytochemistry images (performed as in Fig. 3B) from one of three independent cotransfection experiments with an empty vector (Control) or PGC-1β- encoding vector (PGC-1β) and GFP (ratio GFP:PGC-1β 1:10) of Mfn2 −/−mouse embryonic fibroblasts (MEFs). Transfected cells were visualized by GFP fluorescence (data not shown). Scale bar, 10 µm. (D) Mfn2 −/− mouse embryonic fibroblasts (MEF) quantification and classification attending to mitochondrial tubule length (100–250 transfected cells counted per independent experiment). Mfn2 −/− MEFs with a mean mitochondrial tubule length <4 µm were considered “Short” and >4 µm were considered “Long”. “Perinuclear” MEFs displayed most mitochondria surrounding the nucleus (see Figure S4) and a significant percentage of “Fragmented” cells (with tiny spherical mitochondria, see Figure S4) were observed in transfected Mfn2 −/− MEFs. Results are mean±SEM and expressed as percentage of total transfected Mfn2 −/− MEFs counted from three independent cotransfection experiments with an empty vector (white bars) or PGC-1β (black bars) with GFP (empty vector/PGC-1β : GFP ratio 10:1). Transfected cells were observed by GFP fluorescence (data not shown).
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pone-0003613-g004: Mfn2 is required for PGC-1β changes in mitochondrial morphology.(A) Representative immunocytochemistry images (performed as in Fig. 3B) from one of three independent cotransfection experiments with an empty vector (Control) or PGC-1β- encoding vector (PGC-1β) and GFP (ratio GFP:PGC-1β 1:10) of wild-type mouse embryonic fibroblasts (MEFs). Transfected cells were visualized by GFP fluorescence (data not shown). Scale bar, 10 µm. (B) Wild type mouse embryonic fibroblasts (MEF) quantification and classification attending to mitochondrial tubule length (50-75 transfected cells counted per independent experiment). Wild type MEFs with a mean mitochondrial tubule length <4 µm were considered “Short” and >4 µm were considered “Long”. “Perinuclear” MEFs displayed most mitochondria surrounding the nucleus (see Figure S4) and almost no “Fragmented” cells (with tiny spherical mitochondria, see Figure S4) were observed in transfected wild type MEFs. Results are mean±SEM and expressed as percentage of total transfected wild type MEFs counted from three independent cotransfection experiments with an empty vector (white bars) or PGC-1β (black bars) with GFP (empty vector/PGC-1β : GFP ratio 10:1). Transfected cells were observed by GFP fluorescence (data not shown). *, statistical difference at p<0.02. (C) Representative immunocytochemistry images (performed as in Fig. 3B) from one of three independent cotransfection experiments with an empty vector (Control) or PGC-1β- encoding vector (PGC-1β) and GFP (ratio GFP:PGC-1β 1:10) of Mfn2 −/−mouse embryonic fibroblasts (MEFs). Transfected cells were visualized by GFP fluorescence (data not shown). Scale bar, 10 µm. (D) Mfn2 −/− mouse embryonic fibroblasts (MEF) quantification and classification attending to mitochondrial tubule length (100–250 transfected cells counted per independent experiment). Mfn2 −/− MEFs with a mean mitochondrial tubule length <4 µm were considered “Short” and >4 µm were considered “Long”. “Perinuclear” MEFs displayed most mitochondria surrounding the nucleus (see Figure S4) and a significant percentage of “Fragmented” cells (with tiny spherical mitochondria, see Figure S4) were observed in transfected Mfn2 −/− MEFs. Results are mean±SEM and expressed as percentage of total transfected Mfn2 −/− MEFs counted from three independent cotransfection experiments with an empty vector (white bars) or PGC-1β (black bars) with GFP (empty vector/PGC-1β : GFP ratio 10:1). Transfected cells were observed by GFP fluorescence (data not shown).

Mentions: To study whether the change in mitochondrial morphology induced by PGC-1β was mediated mainly through Mfn2 activity, we used mouse embryonic fibroblasts (MEFs) from wild-type and from Mfn2 or Mfn1 KO mice [29]. Overexpression of PGC-1β led to an increase in mitochondrial length of wild-type (Fig. 4A,B) and Mfn1 KO MEFs (data not shown), similarly as observed in C2C12 myoblasts (Fig. 3B,C). Importantly, PGC-1β gain-of- function was unable to promote mitochondrial elongation in Mfn2 KO MEFs (Fig. 4C,D), in conditions in which ETC subunits Cox4 and Uqcrc2 were increased 1.6- and 1.5-fold respectively (data not shown). These data demonstrate the requirement of Mfn2 expression for PGC-1β-mediated changes in mitochondrial morphology.


Mitochondrial fusion is increased by the nuclear coactivator PGC-1beta.

Liesa M, Borda-d'Agua B, Medina-Gómez G, Lelliott CJ, Paz JC, Rojo M, Palacín M, Vidal-Puig A, Zorzano A - PLoS ONE (2008)

Mfn2 is required for PGC-1β changes in mitochondrial morphology.(A) Representative immunocytochemistry images (performed as in Fig. 3B) from one of three independent cotransfection experiments with an empty vector (Control) or PGC-1β- encoding vector (PGC-1β) and GFP (ratio GFP:PGC-1β 1:10) of wild-type mouse embryonic fibroblasts (MEFs). Transfected cells were visualized by GFP fluorescence (data not shown). Scale bar, 10 µm. (B) Wild type mouse embryonic fibroblasts (MEF) quantification and classification attending to mitochondrial tubule length (50-75 transfected cells counted per independent experiment). Wild type MEFs with a mean mitochondrial tubule length <4 µm were considered “Short” and >4 µm were considered “Long”. “Perinuclear” MEFs displayed most mitochondria surrounding the nucleus (see Figure S4) and almost no “Fragmented” cells (with tiny spherical mitochondria, see Figure S4) were observed in transfected wild type MEFs. Results are mean±SEM and expressed as percentage of total transfected wild type MEFs counted from three independent cotransfection experiments with an empty vector (white bars) or PGC-1β (black bars) with GFP (empty vector/PGC-1β : GFP ratio 10:1). Transfected cells were observed by GFP fluorescence (data not shown). *, statistical difference at p<0.02. (C) Representative immunocytochemistry images (performed as in Fig. 3B) from one of three independent cotransfection experiments with an empty vector (Control) or PGC-1β- encoding vector (PGC-1β) and GFP (ratio GFP:PGC-1β 1:10) of Mfn2 −/−mouse embryonic fibroblasts (MEFs). Transfected cells were visualized by GFP fluorescence (data not shown). Scale bar, 10 µm. (D) Mfn2 −/− mouse embryonic fibroblasts (MEF) quantification and classification attending to mitochondrial tubule length (100–250 transfected cells counted per independent experiment). Mfn2 −/− MEFs with a mean mitochondrial tubule length <4 µm were considered “Short” and >4 µm were considered “Long”. “Perinuclear” MEFs displayed most mitochondria surrounding the nucleus (see Figure S4) and a significant percentage of “Fragmented” cells (with tiny spherical mitochondria, see Figure S4) were observed in transfected Mfn2 −/− MEFs. Results are mean±SEM and expressed as percentage of total transfected Mfn2 −/− MEFs counted from three independent cotransfection experiments with an empty vector (white bars) or PGC-1β (black bars) with GFP (empty vector/PGC-1β : GFP ratio 10:1). Transfected cells were observed by GFP fluorescence (data not shown).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2570954&req=5

pone-0003613-g004: Mfn2 is required for PGC-1β changes in mitochondrial morphology.(A) Representative immunocytochemistry images (performed as in Fig. 3B) from one of three independent cotransfection experiments with an empty vector (Control) or PGC-1β- encoding vector (PGC-1β) and GFP (ratio GFP:PGC-1β 1:10) of wild-type mouse embryonic fibroblasts (MEFs). Transfected cells were visualized by GFP fluorescence (data not shown). Scale bar, 10 µm. (B) Wild type mouse embryonic fibroblasts (MEF) quantification and classification attending to mitochondrial tubule length (50-75 transfected cells counted per independent experiment). Wild type MEFs with a mean mitochondrial tubule length <4 µm were considered “Short” and >4 µm were considered “Long”. “Perinuclear” MEFs displayed most mitochondria surrounding the nucleus (see Figure S4) and almost no “Fragmented” cells (with tiny spherical mitochondria, see Figure S4) were observed in transfected wild type MEFs. Results are mean±SEM and expressed as percentage of total transfected wild type MEFs counted from three independent cotransfection experiments with an empty vector (white bars) or PGC-1β (black bars) with GFP (empty vector/PGC-1β : GFP ratio 10:1). Transfected cells were observed by GFP fluorescence (data not shown). *, statistical difference at p<0.02. (C) Representative immunocytochemistry images (performed as in Fig. 3B) from one of three independent cotransfection experiments with an empty vector (Control) or PGC-1β- encoding vector (PGC-1β) and GFP (ratio GFP:PGC-1β 1:10) of Mfn2 −/−mouse embryonic fibroblasts (MEFs). Transfected cells were visualized by GFP fluorescence (data not shown). Scale bar, 10 µm. (D) Mfn2 −/− mouse embryonic fibroblasts (MEF) quantification and classification attending to mitochondrial tubule length (100–250 transfected cells counted per independent experiment). Mfn2 −/− MEFs with a mean mitochondrial tubule length <4 µm were considered “Short” and >4 µm were considered “Long”. “Perinuclear” MEFs displayed most mitochondria surrounding the nucleus (see Figure S4) and a significant percentage of “Fragmented” cells (with tiny spherical mitochondria, see Figure S4) were observed in transfected Mfn2 −/− MEFs. Results are mean±SEM and expressed as percentage of total transfected Mfn2 −/− MEFs counted from three independent cotransfection experiments with an empty vector (white bars) or PGC-1β (black bars) with GFP (empty vector/PGC-1β : GFP ratio 10:1). Transfected cells were observed by GFP fluorescence (data not shown).
Mentions: To study whether the change in mitochondrial morphology induced by PGC-1β was mediated mainly through Mfn2 activity, we used mouse embryonic fibroblasts (MEFs) from wild-type and from Mfn2 or Mfn1 KO mice [29]. Overexpression of PGC-1β led to an increase in mitochondrial length of wild-type (Fig. 4A,B) and Mfn1 KO MEFs (data not shown), similarly as observed in C2C12 myoblasts (Fig. 3B,C). Importantly, PGC-1β gain-of- function was unable to promote mitochondrial elongation in Mfn2 KO MEFs (Fig. 4C,D), in conditions in which ETC subunits Cox4 and Uqcrc2 were increased 1.6- and 1.5-fold respectively (data not shown). These data demonstrate the requirement of Mfn2 expression for PGC-1β-mediated changes in mitochondrial morphology.

Bottom Line: Here, we demonstrate that reduced mitochondrial size observed in knock-out mice for the transcriptional regulator PGC-1beta is associated with a selective reduction in Mitofusin 2 (Mfn2) expression, a mitochondrial fusion protein.This PGC-1beta-induced elongation specifically requires Mfn2 as this process is absent in Mfn2-ablated cells.Finally, we show that PGC-1beta increases Mfn2 promoter activity and transcription by coactivating the nuclear receptor Estrogen Related Receptor alpha (ERRalpha).

View Article: PubMed Central - PubMed

Affiliation: Institute for Research in Biomedicine (IRB Barcelona), Barcelona, Spain.

ABSTRACT

Background: There is no evidence to date on whether transcriptional regulators are able to shift the balance between mitochondrial fusion and fission events through selective control of gene expression.

Methodology/principal findings: Here, we demonstrate that reduced mitochondrial size observed in knock-out mice for the transcriptional regulator PGC-1beta is associated with a selective reduction in Mitofusin 2 (Mfn2) expression, a mitochondrial fusion protein. This decrease in Mfn2 is specific since expression of the remaining components of mitochondrial fusion and fission machinery were not affected. Furthermore, PGC-1beta increases mitochondrial fusion and elongates mitochondrial tubules. This PGC-1beta-induced elongation specifically requires Mfn2 as this process is absent in Mfn2-ablated cells. Finally, we show that PGC-1beta increases Mfn2 promoter activity and transcription by coactivating the nuclear receptor Estrogen Related Receptor alpha (ERRalpha).

Conclusions/significance: Taken together, our data reveal a novel mechanism by which mammalian cells control mitochondrial fusion. In addition, we describe a novel role of PGC-1beta in mitochondrial physiology, namely the control of mitochondrial fusion mainly through Mfn2.

Show MeSH
Related in: MedlinePlus