title: Death receptors and caspases but not mitochondria are activated in the GDNF- or BDNF-deprived dopaminergic neurons.
abstract: Neurotrophic factors, including glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF), promote survival of midbrain dopaminergic neurons, but the death pathways activated in the dopaminergic neurons by deprivation of these factors are poorly studied. We show here that deprivation of GDNF or BDNF triggers a novel mitochondria-independent death pathway in the cultured embryonic dopaminergic neurons: cytochrome c was not released from the mitochondria to cytosol, proapoptotic protein Bax was not activated, and overexpressed Bcl-xL did not block the death. Caspases were critically required, because the death was completely blocked by caspase inhibitor BAF [boc-aspartyl(OMe)-fluoromethylketone] and overexpression of dominant-negative mutants of caspase-9, -3, and -7 significantly blocked the death. Also, the death receptor pathway was involved, because blockage of caspase-8 or FADD (Fas-associated protein with death domain), an adapter required for caspase-8 activation, inhibited death induced by GDNF or BDNF deprivation. Ligation of Fas by agonistic anti-Fas antibody induced apoptosis in the GDNF- or BDNF-maintained neurons, and inhibition of Fas by Fas-Fc chimera blocked the death of GDNF- or BDNF-deprived neurons, whereas FAIM(L) (long isoform of Fas apoptosis inhibitory molecule) could control the activity of Fas in the dopaminergic neurons.
authors.affiliation: Institute of Biotechnology, University of Helsinki, FIN-00014 Helsinki, Finland.
authors.forename: Li-ying
authors.initials: LY
authors.lastname: Yu
authors.forename: Mart
authors.initials: M
authors.lastname: Saarma
authors.forename: Urmas
authors.initials: U
authors.lastname: Arumäe
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D034961:Antigens, Nuclear / Q000378:metabolism; D019208:Brain-Derived Neurotrophic Factor / Q000172:deficiency* / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000172:deficiency* / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism; D047468:Immunoprecipitation; D000072200:Ku Autoantigen; D008636:Mesencephalon / Q000166:cytology*; D051379:Mice; D008928:Mitochondria / Q000502:physiology*; D009474:Neurons / Q000378:metabolism*; D053218:Receptors, Death Domain / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection / Q000379:methods; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D034961:Antigens, Nuclear; D019208:Brain-Derived Neurotrophic Factor; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D051100:Glial Cell Line-Derived Neurotrophic Factor; D018398:Homeodomain Proteins; D053218:Receptors, Death Domain; D014157:Transcription Factors; D051020:bcl-X Protein; C103192:butyloxycarbonyl-O-methyl-aspartyl-fluoromethyl ketone; C485184:enhanced green fluorescent protein; C433629:homeobox protein PITX3; D049452:Green Fluorescent Proteins; D014446:Tyrosine 3-Monooxygenase; D020169:Caspases; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen; D019311:Staurosporine; D004298:Dopamine