hNOA1 interacts with complex I and DAP3 and regulates mitochondrial respiration and apoptosis.
Mitochondria are dynamic organelles that play key roles in metabolism, energy production, and apoptosis. Coordination of these processes is essential to maintain normal cellular functions. Here we characterized hNOA1, the human homologue of AtNOA1 (Arabidopsis thaliana nitric oxide-associated protein 1), a large mitochondrial GTPase. By immunofluorescence, immunoelectron microscopy, and mitochondrial subfractionation, endogenous hNOA1 is localized within mitochondria where it is peripherally associated with the inner mitochondrial membrane facing the mitochondrial matrix. Overexpression and knockdown of hNOA1 led to changes in mitochondrial shape implying effects on mitochondrial dynamics. To identify the interaction partners of hNOA1 and to further understand its cellular functions, we performed immunoprecipitation-mass spectrometry analysis of endogenous hNOA1 from enriched mitochondrial fractions and found that hNOA1 interacts with both Complex I of the electron transport chain and DAP3 (death-associated protein 3), a positive regulator of apoptosis. Knockdown of hNOA1 reduces mitochondrial O(2) consumption approximately 20% in a Complex I-dependent manner, supporting a functional link between hNOA1 and Complex I. Moreover, knockdown of hNOA1 renders cells more resistant to apoptotic stimuli such as gamma-interferon and staurosporine, supporting a role for hNOA1 in regulating apoptosis. Thus, based on its interactions with both Complex I and DAP3, hNOA1 may play a role in mitochondrial respiration and apoptosis.
Tang
Tingdong
T
Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, California 92093-0651, USA.
Zheng
Bin
B
Chen
Sheng-Hong
SH
Murphy
Anne N
AN
Kudlicka
Krystyna
K
Zhou
Huilin
H
Farquhar
Marilyn G
MG
D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D002522:Chlorocebus aethiops; D042967:Electron Transport Complex I / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D051336:Mitochondrial Membranes / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D016601:RNA-Binding Proteins; D051381:Rats; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology
D000998:Antiviral Agents; D051017:Apoptosis Regulatory Proteins; C097041:DAP3 protein, human; D004791:Enzyme Inhibitors; D024101:Mitochondrial Proteins; D016601:RNA-Binding Proteins; D012269:Ribosomal Proteins; D007371:Interferon-gamma; D020558:GTP Phosphohydrolases; C539734:NOA1 protein, human; D042967:Electron Transport Complex I; D019311:Staurosporine; D010100:Oxygen