title: Novel pro-survival functions of the Kruppel-like transcription factor Egr2 in promotion of macrophage colony-stimulating factor-mediated osteoclast survival downstream of the MEK/ERK pathway.
abstract: Determining the underlying mechanisms of macrophage colony-stimulating factor (M-CSF)-mediated osteoclast survival may be important in identifying novel approaches for treating excessive bone loss. This study investigates M-CSF-mediated MEK/ERK activation and identifies a downstream effector of this pathway. M-CSF activates MEK/ERK and induces MEK-dependent expression of the immediate early gene Egr2. Inhibition of either MEK1/2 or inhibition of Egr2 increases osteoclast apoptosis. In contrast, wild-type Egr2 or an Egr2 point mutant unable to bind the endogenous repressors Nab1/2 (caEgr2) suppresses basal osteoclast apoptosis and rescues osteoclasts from apoptosis induced by MEK1/2 or Egr2 inhibition. Mechanistically, Egr2 induces pro-survival Blc2 family member Mcl1 while stimulating proteasome-mediated degradation of pro-apoptotic Bim. In addition, Egr2 increased the expression of c-Cbl, the E3 ubiquitin ligase that catalyzes Bim ubiquitination. M-CSF, therefore, promotes osteoclast survival through MEK/ERK-dependent induction of Egr2 to control the Mcl1/Bim ratio, documenting a novel function of Egr2 in promoting survival.
authors.affiliation: Department Biochemistry and Molecular Biology.
authors.forename: Elizabeth W
authors.initials: EW
authors.lastname: Bradley
authors.forename: Ming M
authors.initials: MM
authors.lastname: Ruan
authors.forename: Merry J
authors.initials: MJ
authors.lastname: Oursler
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D051767:Early Growth Response Protein 2 / Q000096:biosynthesis*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D051741:Kruppel-Like Transcription Factors / Q000096:biosynthesis*; D048369:MAP Kinase Kinase 1 / Q000378:metabolism*; D048370:MAP Kinase Kinase 2 / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D054875:Ubiquitination / Q000187:drug effects / Q000502:physiology
chemical_list: D051767:Early Growth Response Protein 2; C497327:Egr2 protein, mouse; D051741:Kruppel-Like Transcription Factors; C579094:Mcl1 protein, mouse; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D025801:Ubiquitin; D016173:Macrophage Colony-Stimulating Factor; D044767:Ubiquitin-Protein Ligases; D048049:Extracellular Signal-Regulated MAP Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482127:Map2k1 protein, mouse; C482129:Map2k2 protein, mouse; D046988:Proteasome Endopeptidase Complex