title: Lifeguard Inhibits Fas Ligand-mediated Endoplasmic Reticulum-Calcium Release Mandatory for Apoptosis in Type II Apoptotic Cells.
abstract: Death receptors are members of the tumor necrosis factor receptor superfamily involved in the extrinsic apoptotic pathway. Lifeguard (LFG) is a death receptor antagonist mainly expressed in the nervous system that specifically blocks Fas ligand (FasL)-induced apoptosis. To investigate its mechanism of action, we studied its subcellular localization and its interaction with members of the Bcl-2 family proteins. We performed an analysis of LFG subcellular localization in murine cortical neurons and found that LFG localizes mainly to the ER and Golgi. We confirmed these results with subcellular fractionation experiments. Moreover, we show by co-immunoprecipitation experiments that LFG interacts with Bcl-XL and Bcl-2, but not with Bax or Bak, and this interaction likely occurs in the endoplasmic reticulum. We further investigated the relationship between LFG and Bcl-XL in the inhibition of apoptosis and found that LFG protects only type II apoptotic cells from FasL-induced death in a Bcl-XL dependent manner. The observation that LFG itself is not located in mitochondria raises the question as to whether LFG in the ER participates in FasL-induced death. Indeed, we investigated the degree of calcium mobilization after FasL stimulation and found that LFG inhibits calcium release from the ER, a process that correlates with LFG blockage of cytochrome c release to the cytosol and caspase activation. On the basis of our observations, we propose that there is a required step in the induction of type II apoptotic cell death that involves calcium mobilization from the ER and that this step is modulated by LFG.
authors.affiliation: From the Cell Signaling and Apoptosis Group and the Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Urresti
authors.affiliation: Laboratory of Experimental Cardiology, Institut de Recerca de l'Hospital Universitari de la Vall d'Hebron, 08035 Barcelona, Spain.
authors.forename: Marisol
authors.initials: M
authors.lastname: Ruiz-Meana
authors.affiliation: From the Cell Signaling and Apoptosis Group and.
authors.forename: Elena
authors.initials: E
authors.lastname: Coccia
authors.affiliation: the Department of Cell Biology and Pathology, Instituto de Neurociencias de Castilla y León, Universidad de Salamanca, Salamanca 37007, Spain, and the Institute of Biomedical Research of Salamanca, Salamanca 37007, Spain.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Arévalo
authors.affiliation: Laboratory of Experimental Cardiology, Institut de Recerca de l'Hospital Universitari de la Vall d'Hebron, 08035 Barcelona, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Castellano
authors.affiliation: Laboratory of Experimental Cardiology, Institut de Recerca de l'Hospital Universitari de la Vall d'Hebron, 08035 Barcelona, Spain.
authors.forename: Celia
authors.initials: C
authors.lastname: Fernández-Sanz
authors.affiliation: From the Cell Signaling and Apoptosis Group and.
authors.forename: Koen M O
authors.initials: KM
authors.lastname: Galenkamp
authors.affiliation: From the Cell Signaling and Apoptosis Group and the Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Planells-Ferrer
authors.affiliation: From the Cell Signaling and Apoptosis Group and.
authors.forename: Rana S
authors.initials: RS
authors.lastname: Moubarak
authors.affiliation: From the Cell Signaling and Apoptosis Group and.
authors.forename: Núria
authors.initials: N
authors.lastname: Llecha-Cano
authors.affiliation: From the Cell Signaling and Apoptosis Group and.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Reix
authors.affiliation: Laboratory of Experimental Cardiology, Institut de Recerca de l'Hospital Universitari de la Vall d'Hebron, 08035 Barcelona, Spain.
authors.forename: David
authors.initials: D
authors.lastname: García-Dorado
authors.affiliation: From the Cell Signaling and Apoptosis Group and the Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain, bruna.barneda@vhir.org.
authors.forename: Bruna
authors.initials: B
authors.lastname: Barneda-Zahonero
authors.affiliation: From the Cell Signaling and Apoptosis Group and the Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain, joan.comella@vhir.org.
authors.forename: Joan X
authors.initials: JX
authors.lastname: Comella
mesh_terms: D000818:Animals; D017209:Apoptosis; D020013:Calcium Signaling; D002460:Cell Line; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D053222:Fas Ligand Protein / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D005260:Female; D006056:Golgi Apparatus / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D034622:RNA Interference; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; C523971:lifeguard protein, mouse
keywords: CD95 (APO-1/Fas); apoptosis; calcium; endoplasmic reticulum (ER); neuron