title: NAIP interacts with hippocalcin and protects neurons against calcium-induced cell death through caspase-3-dependent and -independent pathways.
abstract: Inhibitor-of-apoptosis proteins (IAPs), including neuronal apoptosis inhibitory protein (NAIP), inhibit cell death. Other IAPs inhibit key caspase proteases which effect cell death, but the mechanism by which NAIP acts is unknown. Here we report that NAIP, through its third baculovirus inhibitory repeat domain (BIR3), binds the neuron-restricted calcium-binding protein, hippocalcin, in an interaction promoted by calcium. In neuronal cell lines NSC-34 and Neuro-2a, over-expression of the BIR domains of NAIP (NAIP-BIR1-3) counteracted the calcium-induced cell death induced by ionomycin and thapsigargin. This protective capacity was significantly enhanced when NAIP-BIR1-3 was co-expressed with hippocalcin. Over-expression of the BIR3 domain or hippocalcin alone did not substantially enhance cell survival, but co-expression greatly increased their protective effects. These data suggest synergy between NAIP and hippocalcin in facilitating neuronal survival against calcium-induced death stimuli mediated through the BIR3 domain. Analysis of caspase activity after thapsigargin treatment revealed that caspase-3 is activated in NSC-34, but not Neuro-2a, cells. Thus NAIP, in conjunction with hippocalcin, can protect neurons against calcium-induced cell death in caspase-3-activated and non-activated pathways.
authors.affiliation: Department of Neuroscience, Neurobiology, Box 587, Biomedical Centre, Uppsala University, S-751 23 Uppsala, Sweden.
authors.forename: E A
authors.initials: EA
authors.lastname: Mercer
authors.forename: L
authors.initials: L
authors.lastname: Korhonen
authors.forename: Y
authors.initials: Y
authors.lastname: Skoglösa
authors.forename: P A
authors.initials: PA
authors.lastname: Olsson
authors.forename: J P
authors.initials: JP
authors.lastname: Kukkonen
authors.forename: D
authors.initials: D
authors.lastname: Lindholm
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D051597:Hippocalcin; D006801:Humans; D017403:In Situ Hybridization; D009046:Motor Neurons / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051616:Neuronal Apoptosis-Inhibitory Protein; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection; D020798:Two-Hybrid System Techniques
chemical_list: D002135:Calcium-Binding Proteins; D061945:Caspase Inhibitors; C496691:HPCA protein, human; C496693:Hpca protein, rat; C496800:NAIP protein, human; C496803:Naip6 protein, rat; D009419:Nerve Tissue Proteins; D051616:Neuronal Apoptosis-Inhibitory Protein; D012333:RNA, Messenger; D051597:Hippocalcin; D019284:Thapsigargin; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D019311:Staurosporine; D002118:Calcium