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1.
Neurobiol Dis ; 19(1-2): 129-41, 2005.
Article in English | MEDLINE | ID: mdl-15837568

ABSTRACT

Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterized by the accumulation of extracellular depositions of fibrillar beta-amyloid (A beta), which is derived from the alternative processing of beta-amyloid precursor protein (APP). Although APP is thought to function as a cell surface receptor, its mode of action still remains elusive. In this study, we found that the culture medium derived from cortical neurons treated with an anti-APP antibody triggers the death of naive neurons. Biochemical and immunocytochemical analyses revealed the presence, both in the conditioned medium and in neurons, of increased levels of tumor necrosis factor-alpha and monocyte chemoattractant protein-1. Furthermore, the expression of these proinflammatory mediators occurred through a c-Jun N-terminal protein kinase/c-Jun-dependent mechanism. Taken together, our findings provide evidence for a novel mechanism whereby neuronal APP in its full-length configuration induces neuronal death. Such a mechanism might be relevant to neuroinflammatory processes as those observed in AD.


Subject(s)
Amyloid beta-Protein Precursor/immunology , Amyloid beta-Protein Precursor/metabolism , Binding Sites, Antibody/physiology , Cerebral Cortex/metabolism , Chemokine CCL2/biosynthesis , Neurons/metabolism , Tumor Necrosis Factor-alpha/biosynthesis , Amyloid beta-Protein Precursor/pharmacology , Animals , Cell Survival/physiology , Cells, Cultured , Cerebral Cortex/drug effects , Chemokine CCL2/genetics , Culture Media, Conditioned/pharmacology , Mice , Neurons/drug effects , Tumor Necrosis Factor-alpha/genetics
2.
Eur J Neurosci ; 20(8): 2071-8, 2004 Oct.
Article in English | MEDLINE | ID: mdl-15450086

ABSTRACT

A polyclonal antibody (APP-Ab) raised against the extracellular domain of the beta-amyloid precursor protein (APP) triggers a marked neuronal cell death preceded by activation of Ca(2+)-dependent enzymes, neurite degeneration, oxidative stress and nuclear condensation [Mbebi et al. (2002) J. Biol. Chem., 277, 20979-20990]. We have investigated whether activation of APP by this antibody could promote cell death through cellular Ca2+ homeostasis alteration. We carried out time-lapse recordings of intracellular Ca2+ signals in cultured mice cortical neurons by means of a scanning confocal microscope. When applied in the presence of 2 mm external Ca2+, APP-Ab elicited a long-lasting elevation of the intracellular concentration of Ca2+ ([Ca2+]i). Experiments performed in the absence of external Ca2+ showed that APP-Ab triggers the release of Ca2+ from intracellular stores. The re-admission of external Ca2+ provides an additional rise of Ca2+ most likely through store-operated channels. A pretreatment of the cells with pertussis toxin, to inhibit the activity of Gi/Go proteins, or with the phospholipase C inhibitor, 3-nitrocoumarin, prevented both the APP-dependent elevation of Ca2+ as well as the APP-Ab-mediated cell death. Similarly, the store-operated channel inhibitors, 2-APB or SKF-96365 block both the APP-Ab-dependent Ca2+ entry and the APP-Ab-mediated cell death. Altogether, our data provide functional evidence that APP can perturb intracellular Ca2+ homeostasis by emptying intracellular Ca2+ stores and triggering Ca2+ entry through store-operated channels. In response to APP activation, the long-lasting elevation of [Ca2+]i due to an entry of Ca2+ via store-operated channels appears as a major event that leads to neuronal cell death.


Subject(s)
Amyloid beta-Protein Precursor/physiology , Calcium Signaling/physiology , Calcium/metabolism , Cerebral Cortex/metabolism , Neurons/metabolism , Amyloid beta-Protein Precursor/pharmacology , Animals , Biological Transport/drug effects , Biological Transport/physiology , Calcium Signaling/drug effects , Cells, Cultured , Cerebral Cortex/drug effects , Female , Mice , Mice, Inbred C57BL , Neurons/drug effects , Pregnancy
3.
EMBO J ; 22(24): 6537-49, 2003 Dec 15.
Article in English | MEDLINE | ID: mdl-14657026

ABSTRACT

By altering chromatin structure, histone acetyltransferases (HATs) act as transcriptional regulators. We observed in a model of primary neurons that histone acetylation levels decreased at the onset of apoptosis. The CREB-binding protein (CBP) is a HAT of particular interest because it also acts as a co-activator controlling, among others, CREB-dependent transcriptional activity. It has been demonstrated that CREB exerts neuroprotective functions, but the fate of CBP during neuronal apoptosis remained unclear till now. This work provided evidence that CBP is specifically targeted by caspases and calpains at the onset of neuronal apoptosis, and CBP was futher identified as a new caspase-6 substrate. This ultimately impinged on the CBP/p300 HAT activity that decreased with time during apoptosis entry, whereas total cellular HAT activity remained unchanged. Interestingly, CBP loss and histone deacetylation were observed in two different pathological contexts: amyloid precursor protein-dependent signaling and amyotrophic lateral sclerosis model mice, indicating that these modifications are likely to contribute to neurodegenerative diseases. In terms of function, we demonstrated that fine-tuning of CBP HAT activity is necessary to ensure neuroprotection.


Subject(s)
Acetyltransferases/deficiency , Acetyltransferases/genetics , Caspases/metabolism , Cell Cycle Proteins/genetics , Neurons/enzymology , Animals , Apoptosis/physiology , Caspase 6 , Caspases/genetics , Cell Survival , Cells, Cultured , Cerebellum/cytology , Cerebellum/enzymology , Cyclic AMP Response Element-Binding Protein/metabolism , Histone Acetyltransferases , Histones/isolation & purification , Histones/metabolism , Hydrolysis , Kinetics , Mice , Mice, Inbred Strains , Nerve Degeneration/enzymology , Nerve Degeneration/pathology , Neurons/cytology , Neurons/physiology , Recombinant Proteins/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Transcription Factors , p300-CBP Transcription Factors
4.
J Biol Chem ; 277(23): 20979-90, 2002 Jun 07.
Article in English | MEDLINE | ID: mdl-11877414

ABSTRACT

The aberrant metabolism of beta-amyloid precursor protein (APP) and the progressive deposition of its derived fragment beta-amyloid peptide are early and constant pathological hallmarks of Alzheimer's disease. Because APP is able to function as a cell surface receptor, we investigated here whether a disruption of the normal function of APP may contribute to the pathogenic mechanisms in Alzheimer's disease. To this aim, we generated a specific chicken polyclonal antibody directed against the extracellular domain of APP, which is common with the beta-amyloid precursor-like protein type 2. Exposure of cultured cortical neurons to this antibody (APP-Ab) induced cell death preceded by neurite degeneration, oxidative stress, and nuclear condensation. Interestingly, caspase-3-like protease was not activated in this neurotoxic action suggesting a different mode of cell death than classical apoptosis. Further analysis of the molecular mechanisms revealed a calpain- and calcineurin-dependent proteolysis of the neuroprotective calcium/calmodulin-dependent protein kinase IV and its nuclear target protein cAMP responsive element binding protein. These effects were abolished by the G protein inhibitor pertussis toxin, strongly suggesting that APP binding operates via a GTPase-dependent pathway to cause neuronal death.


Subject(s)
Amyloid beta-Protein Precursor/physiology , Calcium-Calmodulin-Dependent Protein Kinases/metabolism , Cell Death/physiology , Neurons/cytology , Signal Transduction , Animals , Calcium-Calmodulin-Dependent Protein Kinase Type 4 , Cells, Cultured , Cyclic AMP Response Element-Binding Protein/metabolism , GTP Phosphohydrolases/metabolism , Mice , Mice, Knockout , Neurons/enzymology , Oxidative Stress
5.
Mol Cell Neurosci ; 19(2): 216-24, 2002 Feb.
Article in English | MEDLINE | ID: mdl-11860274

ABSTRACT

Amyotrophic lateral sclerosis (ALS) is a motor neuron degenerative disorder caused in a proportion of cases by missense mutations in the gene encoding Cu/Zn superoxide dismutase (Cu/Zn-SOD) which result in unknown, lethal enzymatic activity. Based on a differential screening approach, we show here that the gene encoding the cellular prion protein (PrP(C)) was specifically repressed in a transgenic model of ALS overexpressing the mutant G86R Cu/Zn-SOD. Analysis by Northern blot, semiquantitative RT-PCR, and Western blot revealed that PrP(C) down-regulation, which appeared early in the asymptomatic phase of the pathology, occurred preferentially in those tissues primarily affected by the disease (spinal cord, sciatic nerve, and gastrocnemius muscle). This down-regulation was not accompanied by refolding of the aberrant PrP(Sc) isoform, the agent which causes transmissible spongiform encephalopathies. Furthermore, modification of PrP(C) expression was specifically linked to the presence of the G86R mutant since no changes were observed in transgenic mice overexpressing wild-type Cu/Zn-SOD. PrP(C) has been shown to play a role in the protection against oxidative stress, and we therefore propose that its down-regulation may contribute at least in part to ALS pathogenesis.


Subject(s)
Amyotrophic Lateral Sclerosis/genetics , Down-Regulation/genetics , Mutation/genetics , PrPC Proteins/deficiency , Superoxide Dismutase/genetics , Amyotrophic Lateral Sclerosis/metabolism , Amyotrophic Lateral Sclerosis/physiopathology , Animals , DNA Mutational Analysis , Disease Models, Animal , Gene Library , Genetic Testing , Mice , Mice, Transgenic , Molecular Chaperones/genetics , Molecular Chaperones/metabolism , Muscle, Skeletal/metabolism , PrPC Proteins/genetics , Protein Folding , RNA, Messenger/metabolism , Sciatic Nerve/metabolism , Spinal Cord/metabolism , Superoxide Dismutase/metabolism
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