Assessing Actual Contribution of IF1, Inhibitor of Mitochondrial FoF1, to ATP Homeostasis, Cell Growth, Mitochondrial Morphology, and Cell Viability

Fujikawa, Makoto; Imamura, Hiromi; Nakamura, Junji; Yoshida, Masasuke

doi:10.1074/jbc.m112.345793

Cited by 63 publications

(69 citation statements)

References 28 publications

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“…This work was based on the analysis of cells in which IF 1 was transiently either overexpressed or silenced: in the former case a higher mitochondrial volume was described and the lower mitochondrial volume found in the presence of reduced IF 1 level was ascribed to enhanced autophagy compared with controls. However, Fujikawa et al (32) did not observe any difference between IF 1 knockdown and control HeLa cells. Accordingly, in the present study, the mitochondrial content of This investigation clarifies previous conflicting data concerning the difference between the main bioenergetic parameters of human cancer cells containing high levels of IF 1 protein and stable null IF 1 clones.…”

Section: Discussionmentioning

confidence: 90%

“…According to a recent report (45), when ATP hydrolysis significantly contributes to the maintenance of ⌬ m , the addition of oligomycin results in a ⌬ m collapse even in the presence of IF 1 . The observed higher ⌬ m shown by IF 1 -silenced cells compared with controls appears somehow intriguing because in normoxia IF 1 should not affect F 1 F 0 -ATPase unless uncoupled conditions are considered (32,46), therefore the enhanced ⌬ m seen in IF 1 -silenced cells deserves a different explanation.…”

Section: Discussionmentioning

confidence: 94%

“…In addition, Fujikawa et al (32) reported a nearly 40% ⌬ m increase in IF 1 null cells and proposed that it was the result of an increased ATP hydrolytic activity of the F 1 F 0 -ATPase complex under normoxic conditions. To address these conflicting issues, we first evaluated the respiratory chain activity by assaying the oxygen consumption rate in digitoninpermeabilized cells, and found that removal of IF 1 from cells caused a modest (about 20%) but reproducible decrease in the ADP-induced respiration rate (state 3) (Fig.…”

Section: Shrna-mediatedmentioning

confidence: 99%

See 2 more Smart Citations

The Inhibitor Protein (IF1) of the F1F0-ATPase Modulates Human Osteosarcoma Cell Bioenergetics

Barbato

Sgarbi

Gorini

et al. 2015

Journal of Biological Chemistry

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Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 94%

Section: Shrna-mediatedmentioning

confidence: 99%

See 1 more Smart Citation

The Inhibitor Protein (IF1) of the F1F0-ATPase Modulates Human Osteosarcoma Cell Bioenergetics

Barbato

Sgarbi

Gorini

et al. 2015

Journal of Biological Chemistry

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“…Based on in vitro experiments, we and other researchers showed that silencing of IF1 decreased tumor cell proliferation, while Fujikawa et al [25] indicated that depletion of IF1 did not hamper cell growth. They suggested that the functional role of IF1 in human carcinomas may differ in cancer cells and tumor types.…”

Section: Discussionmentioning

confidence: 93%

Silencing of ATPase Inhibitory Factor 1 Inhibits Cell Growth via Cell Cycle Arrest in Bladder Cancer

Wei¹,

Fukuhara²,

Kawada³

et al. 2015

Pathobiology

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Objective: The role of the ATPase inhibitory factor 1 (IF1) is inhibit the hydrolase activity of F₁F_o-ATPase when oxidative phosphorylation is impaired. It has been demonstrated that IF1 is overexpressed in various carcinomas and mediates tumor cell activities, but the detailed mechanisms of IF1-mediated tumor progression and the link between IF1 and cell cycle progression remain unclear. Herein, we aimed to investigate the potential role of IF1 in cell cycle progression of human bladder cancer (BCa). Methods: The expression of IF1 was analyzed by immunohistochemistry in tumor tissues. Western blot was used to detect protein expression in the cells. Cell proliferation was determined by MTT and colony formation assays. The cell cycle was analyzed using flow cytometry. Results: We firstly showed IF1 was overexpressed in BCa. Silencing of IF1 by small interfering RNA led to a significant decrease in cell proliferation and migration in T24 and UM-UC-3 cells. Importantly, IF1 knockdown caused cell cycle arrest at G₀/G₁ stage and decreased the protein level of cyclin E/cyclin-dependent kinases (cdk) 2 and/or cyclin D/cdk4/cdk6. Conclusion: These results suggest the inhibitory effect of IF1 knockdown on BCa cell proliferation is via the suppression of cyclins and cdks related to G₁/S transition and then induction of G₀/G₁ arrest, and firstly indicate IF1 mediates the tumor cell cycle. We concluded that IF1 may be a novel therapeutic target for BCa.

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“…The primary biological role suggested for IF 1 is to act as an emergency protein that intervenes to inhibit ATP hydrolysis by F 1 F o -ATPase when the proton motive force collapses, for example during anoxia. Experimental support for this role is that human cells where expression of IF 1 has been suppressed have reduced ATP levels relative to untreated cells (19). However, mice in which the gene for IF 1 had been disrupted were viable, suggesting that IF 1 is required only under restricted conditions (20).…”

Section: Discussionmentioning

confidence: 99%

Pathway of binding of the intrinsically disordered mitochondrial inhibitor protein to F ₁ -ATPase

Bason

Montgomery

Leslie

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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The hydrolysis of ATP by the ATP synthase in mitochondria is inhibited by a protein called IF 1. Bovine IF 1 has 84 amino acids, and its N-terminal inhibitory region is intrinsically disordered. In a known structure of bovine F 1-ATPase inhibited with residues 1-60 of IF 1 , the inhibitory region from residues 1-50 is mainly α-helical and buried deeply at the α DP β DP-catalytic interface, where it forms extensive interactions with five of the nine subunits of F 1-ATPase but mainly with the β DP-subunit. As described here, on the basis of two structures of inhibited complexes formed in the presence of large molar excesses of residues 1-60 of IF 1 and of a version of IF 1 with the mutation K39A, it appears that the in-trinsically disordered inhibitory region interacts first with the α E β E-catalytic interface, the most open of the three catalytic interfaces , where the available interactions with the enzyme allow it to form an α-helix from residues 31-49. Then, in response to the hydrolysis of an ATP molecule and the associated partial closure of the interface to the α TP β TP state, the extent of the folded α-helical region of IF 1 increases to residues 23-50 as more interactions with the enzyme become possible. Finally, in response to the hydrolysis of a second ATP molecule and a concomitant 120° rotation of the γ-subunit, the interface closes further to the α DP β DP-state, allowing more interactions to form between the enzyme and IF 1. The structure of IF 1 now extends to its maximally folded state found in the previously observed inhibited complex. rotary catalysis | inhibitory path | folding | binding site A small basic protein, known as IF 1 , found in the matrix of mitochondria, is a potent inhibitor of hydrolysis of ATP by mitochondrial F 1-ATPase (1). This protein also inhibits the ATP hydrolytic activity of the intact mitochondrial F 1 F o-ATPase, but not its ability to synthesize ATP in the presence of a proton motive force (2). Hence, IF 1 is a unidirectional inhibitor of ATP hydrolysis only. Bovine IF 1 is 84 amino acids long (3), and the active form is a homodimer held together by an antiparallel coiled-coil of α-helices from residues 49-81. Its N-terminal region from residues 1-45 provides the inhibitory part of the protein, and the dimeric inhibitor binds to two F 1-ATPase complexes simultaneously (4). A monomeric form of IF 1 comprising residues 1-60 is also an effective inhibitor, and in a structure (known as F 1-I1-60His) of bovine F 1-ATPase inhibited by this monomeric form, the inhibitor is buried deeply in a complex binding site in which the inhibitor interacts with five of the nine constituent subunits of F 1-ATPase (5). The structure of the bound inhibitor protein is dominated by an α-helix from residues 21-50, referred to as the long α-helix, and in the inhibited complex this α-helix occupies a deep groove at one of the three catalytic interfaces of F 1-ATPase, namely the one between the α DP-and β DP-subunits. This groove is lined with residues from α-helices and loops in the C-termina...

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Assessing Actual Contribution of IF1, Inhibitor of Mitochondrial FoF1, to ATP Homeostasis, Cell Growth, Mitochondrial Morphology, and Cell Viability

Cited by 63 publications

References 28 publications

The Inhibitor Protein (IF1) of the F1F0-ATPase Modulates Human Osteosarcoma Cell Bioenergetics

The Inhibitor Protein (IF1) of the F1F0-ATPase Modulates Human Osteosarcoma Cell Bioenergetics

Silencing of ATPase Inhibitory Factor 1 Inhibits Cell Growth via Cell Cycle Arrest in Bladder Cancer

Pathway of binding of the intrinsically disordered mitochondrial inhibitor protein to F ₁ -ATPase

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Assessing Actual Contribution of IF1, Inhibitor of Mitochondrial FoF1, to ATP Homeostasis, Cell Growth, Mitochondrial Morphology, and Cell Viability

Cited by 63 publications

References 28 publications

The Inhibitor Protein (IF1) of the F1F0-ATPase Modulates Human Osteosarcoma Cell Bioenergetics

The Inhibitor Protein (IF1) of the F1F0-ATPase Modulates Human Osteosarcoma Cell Bioenergetics

Silencing of ATPase Inhibitory Factor 1 Inhibits Cell Growth via Cell Cycle Arrest in Bladder Cancer

Pathway of binding of the intrinsically disordered mitochondrial inhibitor protein to F 1 -ATPase

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Product

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Pathway of binding of the intrinsically disordered mitochondrial inhibitor protein to F ₁ -ATPase