Opinion
TRENDS in Pharmacological Sciences
Vol.25 No.5 May 2004
Nuclear and mitochondrial
conversations in cell death:
PARP-1 and AIF signaling
Suk Jin Hong1, Ted M. Dawson1,2 and Valina L. Dawson1,2,3
1
Institute for Cell Engineering and Department of Neurology, Johns Hopkins University School of Medicine,
733 North Broadway Street, Suite 731, Baltimore, MD 21205, USA
2
Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
3
Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
Different cell-death mechanisms control many physiological and pathological processes in humans.
Mitochondria play important roles in cell death through
the release of pro-apoptotic factors such as cytochrome
c and apoptosis-inducing factor (AIF), which activate
caspase-dependent and caspase-independent cell
death, respectively. Poly(ADP-ribose) polymerase 1
(PARP-1) is emerging as an important activator of
caspase-independent cell death. PARP-1 generates the
majority of long, branched poly(ADP-ribose) (PAR) polymers following DNA damage. Overactivation of PARP-1
initiates a nuclear signal that propagates to mitochondria and triggers the release of AIF. AIF then shuttles
from mitochondria to the nucleus and induces peripheral chromatin condensation, large-scale fragmentation
of DNA and, ultimately, cytotoxicity. Identification of
the pro-death and pro-survival signals in the PARP-1mediated cell-death program might provide novel
therapeutic targets in human diseases.
A better understanding of the normal regulation of cell
death and cell survival is crucial for the development of
new, successful therapies for preventing and treating
diseases. Cell death occurs by two well-characterized
mechanisms, necrosis [1] and apoptosis [2]. These distinct
forms of cell death have defined morphological and
biochemical features. Following stroke, trauma, neurodegenerative diseases and other insults, the morphology of
dead neurons often meets the criteria for necrosis,
including morphological characteristics and energy
depletion. However, some biochemical changes are consistent with apoptosis, including phosphatidylserine
exposure, mitochondrial release of cytochrome c, caspase
activation and nuclear chromatin condensation (Figure 1).
Thus, neurons might undergo specialized death programs
during chronic neurodegenerative diseases and following
exposure to cytotoxic compounds, hypoxia, ischemia and
viral infection.
In addition to the classically defined cell-death programs of necrosis and apoptosis, it is becoming clear that
there are death programs, which are unique to cell type
Corresponding author: Valina L. Dawson ([email protected]).
and death stimulus that use common death machinery in
specially defined, carefully choreographed programs.
Poly(ADP-ribose) polymerase 1 (PARP-1)-mediated
release of apoptosis-inducing factor (AIF) appears to be
an important, recently identified, cell-death program.
Although the entire cell-death pathway induced by
PARP-1 activation is not yet known, studies using
pharmacological inhibitors of PARP-1 and genetic knockouts of PARP-1 indicate that PARP-1 activation has a key
role in excitotoxic cell death and ischemic injury in the
nervous system [3– 5] and following several other insults
[6]. AIF seems to be a key mediator of cell-death downstream of PARP-1 activation. Here, we review the link
between AIF and PARP-1 in cell-death signaling.
PARP-1
The DNA-repair and protein-modifying enzyme PARP-1,
which is also called poly(ADP-ribose) synthetase and
poly(ADP-ribose) transferase, is an abundant nuclear
protein that is involved in the DNA-base-excision-repair
system. It belongs to a large family of proteins that
includes PARP-2, PARP-3, vault PARP and tankyrases [7].
Each member of the PARP family shares homology on the
C-terminal catalytic domain of PARP-1. On average,
approximately one molecule of PARP-1 is present per
1000 bp of DNA. In response to DNA damage, PARP-1
activity is rapidly increased up to 500-fold upon binding to
DNA strand nicks and breaks. PARP-1 transfers 50 – 200
residues of PAR to itself and to acceptor proteins such as
histones, DNA polymerases, topoisomerases, DNA ligase-2,
high-mobility-group proteins and transcription factors [8,9].
The synthesis and turnover of ADP-ribose polymers is a
dynamic cellular response to DNA damage (Figure 2).
Because of the rapid activation of PARP-1, the intensity of
PARP-1 activation might be a key factor that regulates
whether cells either die or survive following DNA damage.
As a nick sensor, activation of PARP-1 regulates cellular
repair, transcription and replication of DNA, cytoskeletal
organization, protein degradation and other cellular
activities through (ADP-ribosyl)ation of PARP-1 substrates [10 – 13]. However, excessive DNA damage
generates large branched-chained PAR polymers, which
leads to the activation of a unique cell-death program [6].
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Opinion
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Vol.25 No.5 May 2004
Receptor pathway
Mitochondrial pathway
Phosphatidylserine
FasL
Fas
p53
FADD
Bid
Mitochondria
Procaspase-8
BH3-domain proteins
tBid
Bax and Bak
APAF-1
Caspase-8
dATP or ATP
Cytochrome c
Procaspase-9
Procaspase-3
Caspase
activation
Caspase-3
Apoptosome
EndoG
AIF
Nucleus
Chromatin condensation
TRENDS in Pharmacological Sciences
Figure 1. Caspase-dependent cell death. Caspases are a family of cysteine-aspartate proteases that are expressed as inactive proenzymes. Apoptotic signals trigger caspase
activation either by activating initiator caspases such as caspase-8 and caspase-10 (the extrinsic, receptor-mediated pathway) or by the release of caspase-activating factors,
including cytochrome c and apoptosis-inducing factor (AIF), from mitochondria (the intrinsic, mitochondrial pathway). In the extrinsic, receptor-mediated pathway, binding
of Fas ligand (FasL) to Fas activates FADD (Fas-associated via death domain), which cleaves procaspase-8. The resulting caspase-8 cleaves Bid to produce truncated Bid
(tBid) and also activates procaspase-3. Activated caspase-3 causes apoptosis by cleaving substrate proteins, whereas tBid translocates into mitochondria where it induces
Bax- and Bak-mediated permeabilization of the outer mitochondrial membrane and the release of cytochrome c and AIF. In the presence of either dATP or ATP cytochrome
c binds first to apoptotic protease-activating factor 1 (APAF-1) and then to procaspase-9 to form an apoptosome, which activates caspase-3. p53 can also activate Bax and
Bak through BH3-domain proteins or activate Bax directly. AIF and endonuclease G (EndoG) are released from mitochrondria in either a caspase-independent or a caspasedependent manner and translocate to the nucleus, resulting in chromatin condensation. Phosphatidylserine is exposed on the outer leaflet of the plasma membrane in a
caspase-dependent or AIF-dependent manner.
The primary structure of the PARP-1 enzyme is highly
conserved between species. It is a 116-kDa protein that
contains three main functional domains: an N-terminal,
DNA-binding domain (42 kDa) that contains a nuclearlocalization signal; a central automodification domain
(16 kDa); and a C-terminal, catalytic domain (55 kDa)
(Figure 3). The DNA-binding domain utilizes two zincfinger motifs that recognize either single or double-strand
breaks in double-stranded DNA [14,15]. The physiological
functions of PARP-1 and the cellular consequence of
poly(ADP-ribosyl)ation are under investigation. PARP-1mediated
poly(ADP-ribosyl)ation
regulates
gene
expression and amplification, cellular differentiation and
malignant transformation, cellular division and DNA
replication, and mitochondrial function and cell death
[11]. PARP-1 can regulate the activity of promoters directly
[16]. PARP-1 activity stimulates transcription in vitro but,
in the presence of NADþ, it also blocks transcription by
modifying unbound transcription factors and preventing
them binding to DNA [11]. Recent studies in Drosophila
reveal that during transient activation of gene expression
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in response to an environmental stimulus (heat shock)
PARP is recruited to condensed chromatin [17]. PARP
induces dissociation of nucleosomes and decondensation of
chromatin, which facilitates the transcription of target
genes. PARP adds ADP-ribose units to transcription
factors, which prevents them rebinding to DNA [17].
PARP-1 forms a complex with nuclear factor kB (NF-kB)
and can activate the expression of NF-kB target genes [18].
Inhibition of PARP activity also interferes with differentiation in several cellular models. As part of the multiprotein replication complex, PARP-1 is also involved
regulating DNA replication in different cells [13]. PARP-1
can interact with centromere proteins and might regulate
centromere function [19]. Under normal physiological
conditions, PARP-1 activity is important for the regulation of cellular homeostasis and the maintenance of
genomic stability.
In pathological conditions, PARP-1 acquires new
activities that participate in cytotoxicity. Either deficiency
or inhibition of PARP-1 elicits cytoprotection in several
disease models including ischemia – reperfusion injury,
Opinion
TRENDS in Pharmacological Sciences
261
Vol.25 No.5 May 2004
Excessive damage
Mild damage
Oxyradicals,
peroxinitrite,
alkylating agents,
irradiation
MPT
p53
AIF
Transcription
Damage
EndoG
PARG
Caspase-independent
PARP-1
Repair
PARG
Free PAR polymer
and PAR-bound proteins
Nuclear damage signal
NAD+
Nucleus
ATP
TRENDS in Pharmacological Sciences
Figure 2. Caspase-independent cell death in poly(ADP-ribose) polymerase 1 (PARP-1)-mediated cell death. Cell death can occur independently of caspases [54]. For
example, death-domain receptors induce cell death by necrosis when the caspase cascade is inhibited [55] and p53 induces cell death in apoptotic protease-activating factor 1 (APAF-1)-knockout mice [48]. In PARP-1-mediated cell death, overactivation of PARP-1 by toxic insult induces nuclear cell-death signaling (decreased NADþ and ATP)
and causes apoptosis-inducing factor (AIF) to translocate from mitochondria to the nucleus. The dependence of AIF translocation on PARP-1 activation indicates that PARP
signaling might be involved in the release of AIF from mitochondria. Reactive oxygen species (ROS) and other DNA-damaging agents might activate the mitochondrial permeability transition (MPT), which leads to the release of AIF. MPT generates more ROS from mitochondria in a feed-forward mechanism. It is not known whether endonuclease G (EndoG) translocates in PARP-1-mediated cell death, but it is possible that AIF and EndoG act together to mediate caspase-independent cell death [42]. Poly(ADPribose) glycohydrolase (PARG) degrades poly(ADP-ribose) (PAR) polymers, generating free PAR polymer and ADP-ribose. Mild damage to DNA activates the DNA repair
machinery. However, severe insults that result in massive DNA damage will induce PARP-1 overactivation and cell death.
diabetes, inflammatory-mediated injury, reactive oxygen
species-induced injury, glutamate excitotoxicity and the
1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine injury model
[6,20,21]. Although PARP-1 was first investigated in models
of cell injury, other PARP family members might also play a
role in cell death because overexpression of tankyrase 2
causes cytotoxicity [22].
How overactivation of PARP-1 leads to cell death is
under investigation. Some studies indicate a direct action
on mitochondrial function. Peroxynitrite damages mitochondria, which results in: (i) changes in ultrastructural
integrity; (ii) a reduction in the mitochondrial membrane
potential; (iii) an increase in reactive oxygen generation;
(iv) cardiolipin degradation; and (v) mobilization of
intracellular Ca2þ. Peroxynitrite-induced mitochondrial
changes are not observed in mitochondria from PARP-1deficient thymocytes [23]. A recent report suggests that
PARP-1 localizes to mitochondria and, thus, could directly
mediate these effects [24]. However, other investigations
using carefully controlled subcellular fractions have not
observed mitochondrial localization of PARP-1 [25]. A
more common hypothesis of PARP-1-mediated cell injury
involves the observation that overactivation of PARP-1
and (ADP-ribosyl)ation leads to massive utilization of
DNA-binding domain Automodification domain
Catalytic domain
1
1014
Human NH
2
PARP-1
COOH
BRCT
ZF
ZF
NLS
Active
site
Oxidoreductase domain
1
AIF
613
COOH
NH2
MLS Spacer
NLS
NLS
TRENDS in Pharmacological Sciences
Figure 3. Primary structure of poly(ADP-ribose) polymerase 1 (PARP-1) and apoptosis-inducing factor (AIF). Human PARP-1 contains a DNA-binding domain, an automodification domain and a catalytic domain. AIF has an oxidoreductase domain. Abbreviations: BRCT, BRCA1 C-terminal domain; MLS, mitochondrial localization signal; NLS,
nuclear localization signal; ZF, zinc finger motif.
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262
Opinion
TRENDS in Pharmacological Sciences
NADþ and a rapid loss of cellular NADþ and ATP [26]. This
observation has led to the ‘suicide hypothesis’, in which
rapid catabolism of NADþ by PARP-1 activation affect
cellular energy metabolism and, ultimately, lead to cell
death [27,28]. However, direct evidence that energy
depletion has a role in PARP-1-dependent cell death is
lacking. Following PARP-1 activation, NADþ and ATP
depletion are early events in the nervous system, but
neurons die hours later, which indicates that other
downstream mediators might be required for cell death.
Whereas inhibitors and genetic deletion of PARP-1
preserve NADþ and ATP levels, recent data indicate that
preservation of energy stores in PARP-1-knockout mice
does not underlie the reduction in infarct volume following
focal ischemic injury [29]. Although PARP-1-knockout
animals have smaller infarct volumes compared with wildtype animals [29], the time-course and severity of the
apparent diffusion coefficient, an in vivo measure of
cellular energy stores, is equivalent between wild-type
and PARP-1-knockout mice. Thus, energy depletion alone
might not be sufficient to mediate PARP-1-dependent cell
death [11].
PAR polymer
Poly(ADP-ribosyl)ated proteins and/or the PAR polymer
itself might also contribute to PARP-1-mediated cell death
(Figure 2). Many cytoplasmic and nuclear proteins are
substrates of PARPs and are, thus, modified covalently by
PAR [30,31]. Poly(ADP-ribosyl)ation of acceptor proteins
by PARP-1 modifies the charge distribution of acceptor
proteins and increases the hindrance of proteins by the
addition of a bulky and complex structure. This modification might inhibit the physiological function of acceptor
proteins and, thus, severe poly(ADP-ribosyl)ation of key
cellular proteins might lead to cell death. Another
possibility is that the PAR polymer might participate
directly in cell-death signaling. Many cellular proteins
bind to the PAR polymer directly and there is a predicted
consensus motif to which the PAR polymer binds [12]. The
binding of PAR polymer to this consensus motif, which is
composed of hydrophobic and basic amino-acid residues, is
remarkably specific and strong [32]. In this regard, specific
interactions between PAR polymer and another macromolecule could lead to additional signaling routes in many
cellular responses. Several proteins interact strongly with
PAR in a non-covalent fashion [31,32]. Many of these
proteins are related to apoptosis, such as p53, p21 and
caspases [32,33]. Thus, PAR polymer might be a novel
signaling molecule that is produced following activation of
PARP. Although cell-death signaling mediated by the PAR
polymer needs to be studied further, it is conceivable that
PAR polymer might activate cell-death effectors and
interfering with PAR polymer signaling might be an
attractive therapeutic target.
AIF
The cell-death pathway initiated by PARP-1 activation
appears to be mediated by AIF [6,25]. PARP-1 activators,
including the DNA-alkylating agent N-methyl-N0 -nitro-Nnitrosoguanidine, hydrogen peroxide (H2O2) and NMDA
induce the translocation of AIF from mitochondria to the
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Vol.25 No.5 May 2004
nucleus, nuclear condensation, annexin-V staining,
dissipation of the mitochondrial membrane potential and
cell death (Figure 2 and Figure 4). Each of these events is
caspase independent because broad-spectrum caspase
inhibitors do not block them. However, each process is
prevented by the presence of PARP-1 inhibitors and in
PARP-1 knockouts. Translocation of AIF occurs quickly
after PARP-1 activation and precedes cytochrome c release
and caspase activation. Although caspases might be
involved in facilitating cell death, they are not required
because broad-spectrum caspase inhibitors do not prevent
PARP-1-mediated cell death. By contrast, neutralizing
antibodies to AIF do block PARP-1-dependent cell death.
Taken together, these results indicate that AIF is an
essential downstream effector of the cell-death program
initiated by PARP-1 [6,25].
AIF translocates from the mitochondria to the nucleus
where it mediates chromatin condensation and large-scale
fragmentation of DNA, possibly by binding to DNA [34,35].
The mechanism responsible for PARP-1-dependent release
of AIF from mitochondria remains to be identified, but it
might involve PAR signaling (Figure 2 and Figure 4). In
addition to caspase activation [36], disruption of mitochondrial membrane potential, activation and oligomerization of Bax and Bak, mitochondrial permeability
transition and mitochondrial fission might induce the
release of AIF. Therefore AIF release from mitochondria
can be independent and dependent on caspase. There are
Glutamate
Ca2+
NMDA receptor
Mitochondria
Energy
production
ROS
Ca2+
nNOS
Respiration
NO
O2 •−
ONOO−
AIF
ONOO−
Nucleus
DNA damage
DNA fragmentation,
nuclear condensation
PARP
Poly-ADP ribosylation
PARG
Nicotinamide
NAD+
Energy depletion
+4ATP
TRENDS in Pharmacological Sciences
Figure 4. The roles of poly(ADP-ribose) polymerase 1 (PARP-1) and apoptosis-inducing factor (AIF) in glutamate-induced excitotoxicity. Excitotoxic concentrations of
glutamate increase Ca2þ influx through the NMDA receptor, which leads to the
activation of neuronal nitric oxide synthase (nNOS) and production of nitric oxide
(NO). Mitochondrial uptake of Ca2þ, and peroxynitrite (ONOO2), which is generated from the interaction of NO and superoxide anion (Oz2
2 ), both block mitochondrial respiration, which results in the generation of reactive oxygen species (ROS)
and inhibits energy production. Diffusion of peroxynitrite into the nucleus induces
DNA damage followed by PARP-1 activation. Overactivation of PARP-1 consumes
NADþ in the process of poly(ADP-ribosyl)ation. Because ATP is used for recycling
nicotinamide, this reaction depletes cellular energy. Overactivation of PARP-1 triggers a poly(ADP-ribosyl)ation-dependent mechanism that relocates AIF from mitochondria to the nucleus. In the nucleus, AIF promotes DNA fragmentation and
nuclear condensation. Abbreviation: PARG, poly(ADP-ribose) glycohydrolase.
Opinion
TRENDS in Pharmacological Sciences
no known inhibitors of AIF. The broad-spectrum cytoprotective molecules Bcl-2 and a member of the heat shock
protein 70 family [37,38] can delay or prevent AIFmediated toxicity, but their mechanism of action is
unknown. Pharmacological agents that hinder the
translocation of AIF or inhibit the promotion of DNA
fragmentation induced by AIF might have tremendous
therapeutic potential.
Mammalian AIF is a 67-kDa protein that contains a
flavin adenine dinucleotide (FAD)-binding domain that is
similar to bacterial oxidoreductases (Figure 1) [35]. AIF
has both NAD(P)H oxidase and monodehydroascorbate
reductase activity [39]. The amino acid sequences that
interact with FAD and NADH have been mapped [40].
Mutational analysis reveals that AIF induces apoptosis
exclusive of the FAD binding activity [39,41], which
indicates that the oxidoreductase activity of AIF is not
required for its apoptogenic property. There is a strong,
positive, electrostatic potential at the surface of AIF
protein, which indicates that this domain might bind to
DNA [40], and mutants of AIF that are defective in DNA
binding fail to induce cell death, which indicates that the
DNA-binding activity of AIF is necessary for cell death
activity [34]. The mechanism of AIF-mediated chromatin
condensation and DNA fragmentation in cell death is
unclear, but AIF might bind to DNA and recruit proteases
and nucleases that cause chromatin condensation.
Another possibility is that AIF could have a concealed
nuclease activity. In Caenorhabditis elegans, WAH1, a
homolog of AIF, associates with CPS-6, the homolog of
mammalian endonuclease G. This association enhances
the nuclease activity of CPS-6 and results in apoptotic
DNA degradation [42]. Recently, WAH1 and CPS-6 have
been shown to join with nucleases such as CRN1 in a
nuclear complex (the degradasome) to influence nuclease
activity [43].
Although the mitochondrial function of AIF is unknown
currently, structural similarity to flavoproteins indicates
that AIF might act as an oxidoreductase in mitochondrial
electron transport [44]. Cerebellar granule cells from
Harlequin (Hq) mice in which AIF expression is reduced
markedly are susceptible to oxidative stress [45]. The
mitochondrial localization, sensitivity to oxidative stress
in Hq mice and NADH oxidase activity of AIF indicates
that AIF might be involved in scavenging reactive oxygen
species in normal cells. Although AIF might function as a
free-radical scavenger to prevent apoptosis under normal
physiological circumstances, it is also evident that AIF is
an important factor for apoptosis. Cortical neurons from
Hq and wild-type mice are equally sensitive to hydrogen
peroxide-induced injury. Although the translocation of AIF
was not determined, there is sufficient AIF in Hq neurons
to mediate AIF-dependent cell death. From genetic
studies, embryonic stem cells that are deficient in AIF
are resistant to apoptosis induced by either serum
deprivation or menadione (reactive oxygen species stress)
[46]. The suitable removal of cells during embryogenesis is
defective in embryos of AIF-null mice, which results in
embryonic lethality at gastrulation [46]. Parallels can be
drawn between and AIF and cytochrome c: both are
important for cell viability when they are located in
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263
mitochondria, but when either is released from the
mitochondria, they activate death programs.
AIF induces caspase-independent cell death primarily.
Following AIF translocation, classic apoptotic features,
such as phosphatidylserine exposure, partial chromatin
condensation and nuclear condensation, occur in the
absence of caspase activation [25,41,47,48]. AIF appears
to play an important role in the acute neurotoxicity
induced by trauma, hypoglycemia, transient ischemia and
chronic neurodegenerative diseases. AIF translocates in
several experimental models of neurodegeneration,
including the death of photoreceptors induced by retinal
detachment [49], the in vivo neuronal death induced by
brain trauma [50] and cerebral ischemia [51], the death of
cortical neurons induced in vitro by exposure to heatinactivated Streptococcus pneumoniae [52], hydrogen
peroxide, peroxynitrite [50], the topoisomerase I inhibitor
camptothecin, infection with a p53-expressing adenovirus
[48], the striatal cytotoxicity model of Huntington’s disease
[53], and the excitotoxin NMDA [25]. Under excitotoxic
conditions, the NMDA-induced mitochondrial release of
AIF is PARP-1-dependent and caspase-independent and
neutralization of AIF by an AIF-specific antibody
prevents cell death (Figure 4) [25] (H.M. Wang et al.,
unpublished).
Other forms of cell death also involve AIF. In classic
apoptotic paradigms, such as p53 overexpression and
topoisomerase I inhibition, cell death is delayed in the
presence of broad-spectrum inhibitors of caspase and in
cells that lack apoptotic protease activating factor 1, the
core machinery for caspase-dependent cell death [48].
Under these conditions, cells die via an AIF-dependent
mechanism [48]. Thus, therapeutic strategies might need
to block both caspase-dependent and independent pathways to be fully protective against some toxic insults.
Concluding remarks
It appears that the mitochondria and nucleus have crucial
roles in cell death. Understanding the signaling between
these two organelles during cell death might lead to more
options to develop new therapeutic targets for several
diseases that are associated with cell death induced by
mitochondrial dysfunction and nuclear DNA damage. The
molecular mechanisms responsible for PARP-1-dependent
cell death involve the release of AIF from mitochondria
and translocation to the nucleus. Poly(ADP-ribosyl)ation
of cellular proteins might activate the relocation of AIF.
However, the factors and the mechanisms of mitochondrial
AIF expulsion remain to be elucidated. The identification
of the AIF-binding factors that trigger relocation from the
mitochondria to the nucleus and contribute to chromatin
condensation in the nucleus might be particularly important in the development of new pharmaceutical targets.
PARP-1-dependent cell death was noted first in the CNS,
but was followed rapidly by the appreciation that this
program also operated in many other organ systems.
Although the role of PARP-1– AIF interactions has been
appreciated largely in the nervous system to date, we
suspect that soon the importance of this interaction will be
observed in many different organ systems.
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Acknowledgements
This work was supported by grants from the National Institutes of Health,
the Robert Packard Center for ALS Research at Johns Hopkins Medical
Institutions, the American Heart Association and the Mary Lou
McIlhaney Scholar Award.
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References
1 Walker, N.I. et al. (1988) Patterns of cell death. Methods Achiev. Exp.
Pathol. 13, 18 – 54
2 Kerr, J.F. et al. (1972) Apoptosis: a basic biological phenomenon with
wide-ranging implications in tissue kinetics. Br. J. Cancer 26, 239– 257
3 Eliasson, M.J. et al. (1997) Poly(ADP-ribose) polymerase gene disruption
renders mice resistant to cerebral ischemia. Nat. Med. 3, 1089–1095
4 Endres, M. et al. (1997) Ischemic brain injury is mediated by the
activation of poly(ADP-ribose)polymerase. J. Cereb. Blood Flow Metab.
17, 1143 – 1151
5 Zhang, J. et al. (1994) Nitric oxide activation of poly(ADP-ribose)
synthetase in neurotoxicity. Science 263, 687 – 689
6 Yu, S.W. et al. Poly(ADP-ribose) polymerase-1 and apoptosis inducing
factor in neurotoxicity. Neurobiol. Dis. (in press)
7 Smith, S. (2001) The world according to PARP. Trends Biochem. Sci. 26,
174 – 179
8 Smulson, M.E. et al. (2000) Roles of poly(ADP-ribosyl)ation and PARP
in apoptosis, DNA repair, genomic stability and functions of p53 and
E2F-1. Adv. Enzyme Regul. 40, 183 – 215
9 Shall, S. and de Murcia, G. (2000) Poly(ADP-ribose) polymerase-1:
what have we learned from the deficient mouse model? Mutat. Res.
460, 1 – 15
10 Bouchard, V.J. et al. (2003) PARP-1, a determinant of cell survival in
response to DNA damage. Exp. Hematol. 31, 446 – 454
11 Chiarugi, A. (2002) Poly(ADP-ribose) polymerase: killer or conspirator?
The ‘suicide hypothesis’ revisited. Trends Pharmacol. Sci. 23, 122–129
12 Gagne, J.P. et al. (2003) A proteomic approach to the identification of
heterogeneous nuclear ribonucleoproteins as a new family of poly
(ADP-ribose)-binding proteins. Biochem. J. 371, 331– 340
13 Virag, L. and Szabo, C. (2002) The therapeutic potential of poly(ADPRibose) polymerase inhibitors. Pharmacol. Rev. 54, 375 – 429
14 de Murcia, G. and Menissier de Murcia, J. (1994) Poly(ADP-ribose)
polymerase: a molecular nick-sensor. Trends Biochem. Sci. 19, 172–176
15 Lindahl, T. et al. (1995) Post-translational modification of poly(ADPribose) polymerase induced by DNA strand breaks. Trends Biochem.
Sci. 20, 405 – 411
16 Soldatenkov, V.A. et al. (2002) Transcriptional repression by binding of
poly(ADP-ribose) polymerase to promoter sequences. J. Biol. Chem.
277, 665 – 670
17 Tulin, A. and Spradling, A. (2003) Chromatin loosening by poly(ADP)ribose polymerase (PARP) at Drosophila puff loci. Science 299, 560–562
18 Ullrich, O. et al. (2001) Regulation of microglial expression of integrins
by poly(ADP-ribose) polymerase-1. Nat. Cell Biol. 3, 1035 – 1042
19 Saxena, A. et al. (2002) Centromere proteins Cenpa, Cenpb, and Bub3
interact with poly(ADP-ribose) polymerase-1 protein and are poly
(ADP-ribosyl)ated. J. Biol. Chem. 277, 26921 – 26926
20 Szabo, C. and Dawson, V.L. (1998) Role of poly(ADP-ribose) synthetase
in inflammation and ischaemia- reperfusion. Trends Pharmacol. Sci.
19, 287 – 298
21 Wang, H. et al. (2003) Apoptosis inducing factor and PARP-mediated
injury in the MPTP mouse model of Parkinson’s disease. Ann. New
York Acad Sci 991, 132 – 139
22 Kaminker, P.G. et al. (2001) TANK2, a new TRF1-associated poly(ADPribose) polymerase, causes rapid induction of cell death upon
overexpression. J. Biol. Chem. 276, 35891 – 35899
23 Virag, L. et al. (1998) Poly(ADP-ribose) synthetase activation mediates
mitochondrial injury during oxidant-induced cell death. J. Immunol.
161, 3753 – 3759
24 Du, L. et al. (2003) Intra-mitochondrial poly(ADP-ribosylation)
contributes to NAD þ depletion and cell death induced by oxidative
stress. J. Biol. Chem. 278, 18426 – 18433
25 Yu, S.W. et al. (2002) Mediation of poly(ADP-ribose) polymerase-1dependent cell death by apoptosis-inducing factor. Science 297, 259–263
26 Ha, H.C. and Snyder, S.H. (2000) Poly(ADP-ribose) polymerase-1 in
the nervous system. Neurobiol. Dis. 7, 225 – 239
27 Berger, S.J. et al. (1986) Metabolic consequences of DNA damage: DNA
damage induces alterations in glucose metabolism by activation of
www.sciencedirect.com
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poly(ADP-ribose) polymerase. Biochem. Biophys. Res. Commun. 134,
227–232
Berger, N.A. et al. (1983) Poly(ADP-ribose) polymerase mediates the
suicide response to massive DNA damage: studies in normal and DNArepair defective cells. Princess Takamatsu Symp. 13, 219– 226
Goto, S. et al. (2002) Poly(ADP-ribose) polymerase impairs early and
long-term experimental stroke recovery. Stroke 33, 1101 – 1106
Du, X. et al. (2003) Inhibition of GAPDH activity by poly(ADP-ribose)
polymerase activates three major pathways of hyperglycemic damage
in endothelial cells. J. Clin. Invest. 112, 1049 – 1057
D’Amours, D. et al. (1999) Poly(ADP-ribosyl)ation reactions in the
regulation of nuclear functions. Biochem. J. 342, 249 – 268.
Pleschke, J.M. et al. (2000) Poly(ADP-ribose) binds to specific domains
in DNA damage checkpoint proteins. J. Biol. Chem. 275, 40974 – 40980
Vaziri, H. et al. (1997) ATM-dependent telomere loss in aging human
diploid fibroblasts and DNA damage lead to the post-translational
activation of p53 protein involving poly(ADP-ribose) polymerase.
EMBO J. 16, 6018 – 6033
Ye, H. et al. (2002) DNA binding is required for the apoptogenic action
of apoptosis inducing factor. Nat. Struct. Biol. 9, 680 – 684
Susin, S.A. et al. (1999) Molecular characterization of mitochondrial
apoptosis-inducing factor. Nature 397, 441 – 446
Arnoult, D. et al. (2003) Mitochondrial release of AIF and EndoG
requires caspase activation downstream of Bax/Bak-mediated permeabilization. EMBO J. 22, 4385 – 4399
Ravagnan, L. et al. (2001) Heat-shock protein 70 antagonizes
apoptosis-inducing factor. Nat. Cell Biol. 3, 839 – 843
Ruchalski, K. et al. (2003) HSP72 inhibits apoptosis-inducing factor
release in ATP depleted renal epithelial cells. Am. J. Physiol. Cell
Physiol. 285, 1483 – 1493
Miramar, M.D. et al. (2001) NADH oxidase activity of mitochondrial
apoptosis-inducing factor. J. Biol. Chem. 276, 16391 – 16398
Mate, M.J. et al. (2002) The crystal structure of the mouse apoptosisinducing factor AIF. Nat. Struct. Biol. 9, 442 – 446
Loeffler, M. et al. (2001) Dominant cell death induction by extramitochondrially targeted apoptosis-inducing factor. FASEB J. 15, 758–767
Wang, X. et al. (2002) Mechanisms of AIF-mediated apoptotic DNA
degradation in Caenorhabditis elegans. Science 298, 1587 – 1592
Parrish, J.Z. et al. (2003) CRN-1, a Caenorhabditis elegans FEN-1
homologue, cooperates with CPS-6/EndoG to promote apoptotic DNA
degradation. EMBO J. 22, 3451 – 3460
Lipton, S.A. and Bossy-Wetzel, E. (2002) Dueling activities of AIF in cell
death versus survival: DNA binding and redox activity. Cell 111, 147–150
Klein, J.A. et al. (2002) The harlequin mouse mutation downregulates
apoptosis-inducing factor. Nature 419, 367 – 374
Joza, N. et al. (2001) Essential role of the mitochondrial apoptosisinducing factor in programmed cell death. Nature 410, 549 – 554
Susin, S.A. et al. (2000) Two distinct pathways leading to nuclear
apoptosis. J. Exp. Med. 192, 571 – 580
Cregan, S.P. et al. (2002) Apoptosis-inducing factor is involved in the
regulation of caspase-independent neuronal cell death. J. Cell Biol.
158, 507 – 517
Hisatomi, T. et al. (2002) Critical role of photoreceptor apoptosis in
functional damage after retinal detachment. Curr. Eye Res. 24, 161–172
Zhang, X. et al. (2002) Intranuclear localization of apoptosis-inducing
factor (AIF) and large scale DNA fragmentation after traumatic brain
injury in rats and in neuronal cultures exposed to peroxynitrite.
J. Neurochem. 82, 181 – 191
Zhu, C. et al. (2003) Involvement of apoptosis-inducing factor in
neuronal death after hypoxia-ischemia in the neonatal rat brain.
J. Neurochem. 86, 306 – 317
Braun, J.S. et al. (2001) Apoptosis-inducing factor mediates microglial
and neuronal apoptosis caused by pneumococcus. J. Infect. Dis. 184,
1300– 1309
Wang, X. et al. (2003) Minocycline inhibits caspase-independent
and -dependent mitochondrial cell death pathways in models of
Huntington’s disease. Proc. Natl. Acad. Sci. U. S. A. 100,
10483 – 10487
Leist, M. and Jaattela, M. (2001) Four deaths and a funeral: from
caspases to alternative mechanisms. Nat. Rev. Mol. Cell Biol. 2, 589–598
Denecker, G. et al. (2001) Death receptor-induced apoptotic and
necrotic cell death: differential role of caspases and mitochondria. Cell
Death Differ. 8, 829– 840