Mitochondrial Dok-4 recruits Src kinase and regulates NF-κB activation in endothelial cells

Seigo Itoh, Serge Lemay, Masaki Osawa, Wenyi Che, Yuntao Duan, Andrew Tompkins, Paul S. Brookes, Shey Shing Sheu, Jun Ichi Abe

Research output: Contribution to journalArticle

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Abstract

The downstream of kinase (Dok) family of adapter proteins consists of at least five members structurally characterized by an NH2-terminal tandem of conserved pleckstrin homology and phosphotyrosine binding domains linked to a unique COOH-terminal region. To determine the role of the novel adapter protein Dok-4 in endothelial cells, we first investigated the cell localization of Dok-4. Most surprisingly, immunofluorescence microscopy, cell fractionation studies, and studies with enhanced green fluorescent protein chimeras showed that wild type Dok-4 (Dok-4-WT) specifically localized in mitochondria. An NH2-terminal deletion mutant of Dok-4 (Dok-4-(ΔN11-29)), which lacks the mitochondrial targeting sequence, could not accumulate in mitochondria. Co-immunoprecipitation revealed an interaction of c-Src with Dok-4-WT in endothelial cells. Most interestingly, overexpression of Dok-4-WT, but not Dok-4-(ΔN1-99), increased mitochondrial c-Src expression, whereas knock-down of endogenous Dok-4 with a small interfering RNA vector greatly inhibited mitochondrial localization of c-Src, suggesting a unique function for Dok-4 as an anchoring protein for c-Src in mitochondria. Dok-4-WT significantly decreased 39-kDa subunit complex I expression. PP2, a specific Src kinase inhibitor, prevented the Dok-4-mediated complex I decrease, suggesting the involvement of Src kinase in regulation of complex I expression. Dok-4-WT enhanced tumor necrosis factor-α (TNF-α)-mediated reactive oxygen species (ROS) production, supporting the functional relevance of a Dok-4-Src-complex I/ROS signaling pathway in mitochondria. Finally, Dok-4 enhanced TNF-alpha;-mediated NF-κB activation, whereas this was inhibited by transfection with Dok-4 small interfering RNA. In addition, Dok-4-induced NF-κB-activation was also inhibited by transfection of a dominant negative form of c-Src. These data suggest a role for mitochondrial Dok-4 as an anchoring molecule for the tyrosine kinase c-Src, and in turn as a regulator of TNF-α-mediated ROS production and NF-κB activation.

Original languageEnglish (US)
Pages (from-to)26383-26396
Number of pages14
JournalJournal of Biological Chemistry
Volume280
Issue number28
DOIs
StatePublished - Jul 15 2005

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src-Family Kinases
Endothelial cells
Phosphotransferases
Endothelial Cells
Chemical activation
Mitochondria
Reactive Oxygen Species
Tumor Necrosis Factor-alpha
Small Interfering RNA
Transfection
Cell Fractionation
Phosphotyrosine
Proteins

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Mitochondrial Dok-4 recruits Src kinase and regulates NF-κB activation in endothelial cells. / Itoh, Seigo; Lemay, Serge; Osawa, Masaki; Che, Wenyi; Duan, Yuntao; Tompkins, Andrew; Brookes, Paul S.; Sheu, Shey Shing; Abe, Jun Ichi.

In: Journal of Biological Chemistry, Vol. 280, No. 28, 15.07.2005, p. 26383-26396.

Research output: Contribution to journalArticle

Itoh, S, Lemay, S, Osawa, M, Che, W, Duan, Y, Tompkins, A, Brookes, PS, Sheu, SS & Abe, JI 2005, 'Mitochondrial Dok-4 recruits Src kinase and regulates NF-κB activation in endothelial cells', Journal of Biological Chemistry, vol. 280, no. 28, pp. 26383-26396. https://doi.org/10.1074/jbc.M410262200
Itoh, Seigo ; Lemay, Serge ; Osawa, Masaki ; Che, Wenyi ; Duan, Yuntao ; Tompkins, Andrew ; Brookes, Paul S. ; Sheu, Shey Shing ; Abe, Jun Ichi. / Mitochondrial Dok-4 recruits Src kinase and regulates NF-κB activation in endothelial cells. In: Journal of Biological Chemistry. 2005 ; Vol. 280, No. 28. pp. 26383-26396.
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AU - Lemay, Serge

AU - Osawa, Masaki

AU - Che, Wenyi

AU - Duan, Yuntao

AU - Tompkins, Andrew

AU - Brookes, Paul S.

AU - Sheu, Shey Shing

AU - Abe, Jun Ichi

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N2 - The downstream of kinase (Dok) family of adapter proteins consists of at least five members structurally characterized by an NH2-terminal tandem of conserved pleckstrin homology and phosphotyrosine binding domains linked to a unique COOH-terminal region. To determine the role of the novel adapter protein Dok-4 in endothelial cells, we first investigated the cell localization of Dok-4. Most surprisingly, immunofluorescence microscopy, cell fractionation studies, and studies with enhanced green fluorescent protein chimeras showed that wild type Dok-4 (Dok-4-WT) specifically localized in mitochondria. An NH2-terminal deletion mutant of Dok-4 (Dok-4-(ΔN11-29)), which lacks the mitochondrial targeting sequence, could not accumulate in mitochondria. Co-immunoprecipitation revealed an interaction of c-Src with Dok-4-WT in endothelial cells. Most interestingly, overexpression of Dok-4-WT, but not Dok-4-(ΔN1-99), increased mitochondrial c-Src expression, whereas knock-down of endogenous Dok-4 with a small interfering RNA vector greatly inhibited mitochondrial localization of c-Src, suggesting a unique function for Dok-4 as an anchoring protein for c-Src in mitochondria. Dok-4-WT significantly decreased 39-kDa subunit complex I expression. PP2, a specific Src kinase inhibitor, prevented the Dok-4-mediated complex I decrease, suggesting the involvement of Src kinase in regulation of complex I expression. Dok-4-WT enhanced tumor necrosis factor-α (TNF-α)-mediated reactive oxygen species (ROS) production, supporting the functional relevance of a Dok-4-Src-complex I/ROS signaling pathway in mitochondria. Finally, Dok-4 enhanced TNF-alpha;-mediated NF-κB activation, whereas this was inhibited by transfection with Dok-4 small interfering RNA. In addition, Dok-4-induced NF-κB-activation was also inhibited by transfection of a dominant negative form of c-Src. These data suggest a role for mitochondrial Dok-4 as an anchoring molecule for the tyrosine kinase c-Src, and in turn as a regulator of TNF-α-mediated ROS production and NF-κB activation.

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