title: Suppression of death receptor signaling in cerebellar Purkinje neurons protects neighboring granule neurons from apoptosis via an insulin-like growth factor I-dependent mechanism.
abstract: Neuronal apoptosis contributes to the progression of neurodegenerative disease. Primary cerebellar granule neurons are an established in vitro model for investigating neuronal death. After removal of serum and depolarizing potassium, granule neurons undergo apoptosis via a mechanism that requires intrinsic (mitochondrial) death signals; however, the role of extrinsic (death receptor-mediated) signals is presently unclear. Here, we investigate involvement of death receptor signaling in granule neuron apoptosis by expressing adenoviral, AU1-tagged, dominant-negative Fas-associated death domain (Ad-AU1-deltaFADD). Ad-AU1-deltaFADD decreased apoptosis of granule neurons from 65 +/- 5 to 27 +/- 2% (n = 7, p < 0.01). Unexpectedly, immunocytochemical staining for AU1 revealed that <5% of granule neurons expressed deltaFADD. In contrast, deltaFADD was expressed in >95% of calbindin-positive Purkinje neurons ( approximately 2% of the cerebellar culture). Granule neurons in proximity to deltaFADD-expressing Purkinje cells demonstrated markedly increased survival. Both granule and Purkinje neurons expressed insulin-like growth factor-I (IGF-I) receptors, and deltaFADD-mediated survival of granule neurons was inhibited by an IGF-I receptor blocking antibody. These results demonstrate that the selective suppression of death receptor signaling in Purkinje neurons is sufficient to rescue neighboring granule neurons that depend on Purkinje cell-derived IGF-I. Thus, the extrinsic death pathway has a profound but indirect effect on the survival of cerebellar granule neurons.
authors.affiliation: Department of Pharmacology, University of Colorado Health Sciences Center and the Denver Veterans Affairs Medical Center, Denver, Colorado 80220, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Linseman
authors.forename: Maria L
authors.initials: ML
authors.lastname: McClure
authors.forename: Ron J
authors.initials: RJ
authors.lastname: Bouchard
authors.forename: Tracey A
authors.initials: TA
authors.lastname: Laessig
authors.forename: Ferogh A
authors.initials: FA
authors.lastname: Ahmadi
authors.forename: Kim A
authors.initials: KA
authors.lastname: Heidenreich
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000256:Adenoviridae; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D064026:Calbindins; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D002531:Cerebellum / Q000502:physiology*; D053200:Fas-Associated Death Domain Protein; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology* / Q000502:physiology; D011689:Purkinje Cells / Q000166:cytology* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000032:analysis; D015398:Signal Transduction; D014162:Transfection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D064026:Calbindins; D002352:Carrier Proteins; C505535:Fadd protein, rat; D053200:Fas-Associated Death Domain Protein; D011994:Recombinant Proteins; D064030:S100 Calcium Binding Protein G; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1