title: POSH acts as a scaffold for a multiprotein complex that mediates JNK activation in apoptosis.
abstract: We report that the multidomain protein POSH (plenty of SH3s) acts as a scaffold for the JNK pathway of neuronal death. This pathway consists of a sequential cascade involving activated Rac1/Cdc42, mixed-lineage kinases (MLKs), MAP kinase kinases (MKKs) 4 and 7, c-Jun N-terminal kinases (JNKs) and c-Jun, and is required for neuronal death induced by various means including nerve growth factor (NGF) deprivation. In addition to binding GTP-Rac1 as described previously, we find that POSH binds MLKs both in vivo and in vitro, and complexes with MKKs 4 and 7 and with JNKs. POSH overexpression promotes apoptotic neuronal death and this is suppressed by dominant-negative forms of MLKs, MKK4/7 and c-Jun, and by an MLK inhibitor. Moreover, a POSH antisense oligonucleotide and a POSH small interfering RNA (siRNA) suppress c-Jun phosphorylation and neuronal apoptosis induced by NGF withdrawal. Thus, POSH appears to function as a scaffold in a multiprotein complex that links activated Rac1 and downstream elements of the JNK apoptotic cascade.
authors.affiliation: Department of Pathology and Center for Neurobiology and Behavior, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
authors.forename: Zhiheng
authors.initials: Z
authors.lastname: Xu
authors.forename: Nickolay V
authors.initials: NV
authors.lastname: Kukekov
authors.forename: Lloyd A
authors.initials: LA
authors.lastname: Greene
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D057846:Cell-Penetrating Peptides; D003546:Cysteine Endopeptidases / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D046911:Macromolecular Substances; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism; D046912:Multiprotein Complexes; D020932:Nerve Growth Factor / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000378:metabolism; D016716:PC12 Cells; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000166:cytology / Q000378:metabolism; D016335:Zinc Fingers; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D057846:Cell-Penetrating Peptides; D003598:Cytoskeletal Proteins; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D046912:Multiprotein Complexes; D016376:Oligonucleotides, Antisense; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; C111370:Sh3md2 protein, mouse; D020932:Nerve Growth Factor; C414409:penetratin; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; D048670:MAP Kinase Kinase 4; C482559:MAP2K4 protein, human; C482562:Map2k4 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D020830:rac1 GTP-Binding Protein