Inactivation of Omi/HtrA2 protease leads to the deregulation of mitochondrial Mulan E3 ubiquitin ligase and increased mitophagy.
Omi/HtrA2 is a nuclear encoded mitochondrial serine protease with dual and opposite functions that depend entirely on its subcellular localization. During apoptosis, Omi/HtrA2 is released into the cytoplasm where it participates in cell death. While confined in the inter-membrane space of the mitochondria, Omi/HtrA2 has a pro-survival function that may involve the regulation of protein quality control (PQC) and mitochondrial homeostasis. Loss of Omi/HtrA2's protease activity causes the neuromuscular disorder of the mnd2 (motor neuron degeneration 2) mutant mice. These mice develop multiple defects including neurodegeneration with parkinsonian features. Loss of Omi/HtrA2 in non-neuronal tissues has also been shown to cause premature aging. The normal function of Omi/HtrA2 in the mitochondria and how its deregulation causes neurodegeneration or premature aging are unknown. Here we report that the mitochondrial Mulan E3 ubiquitin ligase is a specific substrate of Omi/HtrA2. During exposure to H(2)O(2), Omi/HtrA2 degrades Mulan, and this regulation is lost in cells that carry the inactive protease. Furthermore, we show accumulation of Mulan protein in various tissues of mnd2 mice as well as in Omi/HtrA2(-/-) mouse embryonic fibroblasts (MEFs). This causes a significant decrease of mitofusin 2 (Mfn2) protein, and increased mitophagy. Our work describes a new stress-signaling pathway that is initiated in the mitochondria and involves the regulation of Mulan by Omi/HtrA2 protease. Deregulation of this pathway, as it occurs in mnd2 mutant mice, causes mitochondrial dysfunction and mitophagy, and could be responsible for the motor neuron disease and the premature aging phenotype observed in these animals.
Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL32826, USA.
Lucia
L
Cilenti
Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL32826, USA.
Camilla T
CT
Ambivero
Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL32826, USA.
Nathan
N
Ward
Center for Apoptosis Research, Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, PA19107, USA.
Emad S
ES
Alnemri
Tisch Cancer Institute, Division of Hematology/Oncology, Mount Sinai School of Medicine, New York, NY 10129, USA.
Doris
D
Germain
Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL32826, USA. Electronic address: Antonis.Zervos@ucf.edu.
Antonis S
AS
Zervos
D019588:Aging, Premature / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D020558:GTP Phosphohydrolases / Q000172:deficiency / Q000235:genetics*; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D000074923:High-Temperature Requirement A Serine Peptidase 2; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism* / Q000473:pathology; D024101:Mitochondrial Proteins / Q000172:deficiency / Q000235:genetics*; D063306:Mitophagy / Q000235:genetics*; D016472:Motor Neuron Disease / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018384:Oxidative Stress; D021381:Protein Transport; D012697:Serine Endopeptidases / Q000172:deficiency / Q000235:genetics*; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism
D024101:Mitochondrial Proteins; D044767:Ubiquitin-Protein Ligases; D012697:Serine Endopeptidases; C000615914:HTRA2 protein, human; D000074923:High-Temperature Requirement A Serine Peptidase 2; C000615915:Htra2 protein, mouse; D020558:GTP Phosphohydrolases; C488751:Mfn2 protein, mouse
Apoptosis; Mitophagy; Mulan E3 ubiquitin ligase; Omi/HtrA2; Oxidative stress; mnd2 mouse