title: Eiger-induced cell death relies on Rac1-dependent endocytosis.
abstract: Signaling via tumor necrosis factor receptor (TNFR) superfamily members regulates cellular life and death decisions. A subset of mammalian TNFR proteins, most notably the p75 neurotrophin receptor (p75NTR), induces cell death through a pathway that requires activation of c-Jun N-terminal kinases (JNKs). However the receptor-proximal signaling events that mediate this remain unclear. Drosophila express a single tumor necrosis factor (TNF) ligand termed Eiger (Egr) that activates JNK-dependent cell death. We have exploited this model to identify phylogenetically conserved signaling events that allow Egr to induce JNK activation and cell death in vivo. Here we report that Rac1, a small GTPase, is specifically required in Egr-mediated cell death. rac1 loss of function blocks Egr-induced cell death, whereas Rac1 overexpression enhances Egr-induced killing. We identify Vav as a GEF for Rac1 in this pathway and demonstrate that dLRRK functions as a negative regulator of Rac1 that normally acts to constrain Egr-induced death. Thus dLRRK loss of function increases Egr-induced cell death in the fly. We further show that Rac1-dependent entry of Egr into early endosomes is a crucial prerequisite for JNK activation and for cell death and show that this entry requires the activity of Rab21 and Rab7. These findings reveal novel regulatory mechanisms that allow Rac1 to contribute to Egr-induced JNK activation and cell death.
authors.affiliation: Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
authors.forename: W
authors.initials: W
authors.lastname: Ruan
authors.affiliation: Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Srinivasan
authors.affiliation: Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Lin
authors.affiliation: Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
authors.forename: k-I
authors.initials: kI
authors.lastname: Kara
authors.affiliation: Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.|Department of Biology, The University of British Columbia, Okanagan Campus, Kelowna, British Columbia, Canada.
authors.forename: P A
authors.initials: PA
authors.lastname: Barker
mesh_terms: D000818:Animals; D017209:Apoptosis; D004330:Drosophila / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051567:Proto-Oncogene Proteins c-vav / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D020800:Receptor, Nerve Growth Factor / Q000378:metabolism; D015398:Signal Transduction; D020744:rac GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: C090145:Cdc42 protein, Drosophila; D029721:Drosophila Proteins; D008565:Membrane Proteins; D051567:Proto-Oncogene Proteins c-vav; D034741:RNA, Small Interfering; C090146:Rac1 protein, Drosophila; D020800:Receptor, Nerve Growth Factor; C464573:egr protein, Drosophila; C543697:LRRK protein, Drosophila; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins