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1.
Differential Expression and Internal Feedback Regulation
of
1-Aminocyclopropane-1-Carboxylate Synthase,
1-Aminocyclopropane-1-Carboxylate Oxidase, and
Ethylene Receptor
Genes in Tomato Fruit during Development and Ripening 总被引:22,自引:1,他引:21
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Akira Nakatsuka Shiho Murachi Hironori Okunishi Shinjiro Shiomi Ryohei Nakano Yasutaka Kubo Akitsugu Inaba 《Plant physiology》1998,118(4):1295-1305
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5.
Jens Waak Stephanie S. Weber Karin G?rner Christoph Schall Hidenori Ichijo Thilo Stehle Philipp J. Kahle 《The Journal of biological chemistry》2009,284(21):14245-14257
Parkinson disease (PD)-associated genomic deletions and the destabilizing
L166P point mutation lead to loss of the cytoprotective DJ-1 protein. The
effects of other PD-associated point mutations are less clear. Here we
demonstrate that the M26I mutation reduces DJ-1 expression, particularly in a
null background (knockout mouse embryonic fibroblasts). Thus, homozygous M26I
mutation causes loss of DJ-1 protein. To determine the cellular consequences,
we measured suppression of apoptosis signal-regulating kinase 1 (ASK1) and
cytotoxicity for [M26I]DJ-1, and systematically all other DJ-1 methionine and
cysteine mutants. C106A mutation of the central redox site specifically
abolished binding to ASK1 and the cytoprotective activity of DJ-1. DJ-1 was
apparently recruited into the ASK1 signalosome via Cys-106-linked mixed
disulfides. The designed higher order oxidation mimicking [C106DD]DJ-1
non-covalently bound to ASK1 even in the absence of hydrogen peroxide and
conferred partial cytoprotection. Interestingly, mutations of peripheral redox
sites (C46A and C53A) and M26I also led to constitutive ASK1 binding.
Cytoprotective [wt]DJ-1 bound to the ASK1 N terminus (which is known to bind
another negative regulator, thioredoxin 1), whereas [M26I]DJ-1 bound to
aberrant C-terminal site(s). Consequently, the peripheral cysteine mutants
retained cytoprotective activity, whereas the PD-associated mutant [M26I]DJ-1
failed to suppress ASK1 activity and nuclear export of the death
domain-associated protein Daxx and did not promote cytoprotection. Thus,
cytoprotective binding of DJ-1 to ASK1 depends on the central redox-sensitive
Cys-106 and may be modulated by peripheral cysteine residues. We suggest that
impairments in oxidative conformation changes of DJ-1 might contribute to PD
neurodegeneration.Loss-of-function mutations in the DJ-1 gene (PARK7) cause
autosomal-recessive hereditary Parkinson disease
(PD)2
(1). The most dramatic
PD-associated mutation L166P impairs DJ-1 dimer formation and dramatically
destabilizes the protein
(2–7).
Other mutations such as M26I
(8) and E64D
(9) have more subtle defects
with unclear cellular consequences
(4,
7,
10,
11). In addition to this
genetic association, DJ-1 is neuropathologically linked to PD. DJ-1 is
up-regulated in reactive astrocytes, and it is oxidatively modified in brains
of sporadic PD patients
(12–14).DJ-1 protects against oxidative stress and mitochondrial toxins in cell
culture
(15–17)
as well as in diverse animal models
(18–21).
The cytoprotective effects of DJ-1 may be stimulated by oxidation and mediated
by molecular chaperoning (22,
23), and/or facilitation of
the pro-survival Akt and suppression of apoptosis signal-regulating kinase 1
(ASK1) pathways (6,
24,
25). The cytoprotective
activity of DJ-1 against oxidative stress depends on its cysteine residues
(15,
17,
26). Among the three cysteine
residues of DJ-1, the most prominent one is the easiest oxidizable Cys-106
(27) that is in a constrained
conformation (28), but the
other cysteine residues Cys-46 and Cys-53 have been implicated with DJ-1
activity as well (22).
However, the molecular basis of oxidation-mediated cytoprotective activity of
DJ-1 is not clear. Moreover, the roles of PD-mutated and in vivo
oxidized methionines are not known.Here we have mutagenized all oxidizable residues within DJ-1 and studied
the effects on protein stability and function. The PD-associated mutation M26I
within the DJ-1 dimer interface selectively reduced protein expression as well
as ASK1 suppression and cytoprotective activity in oxidatively stressed cells.
These cell culture results support a pathogenic effect of the clinical M26I
mutation (8). Furthermore,
oxidation-defective C106A mutation abolished binding to ASK1 and
cytoprotective activity of DJ-1, whereas the designed higher order oxidation
mimicking mutant [C106DD]DJ-1 bound to ASK1 even in the absence of
H2O2 and conferred partial cytoprotection. The
peripheral cysteine mutants [C46A]DJ-1 and [C53A]DJ-1 were also cytoprotective
and were incorporated into the ASK1 signalosome even in the basal state. Thus,
DJ-1 may be activated by a complex mechanism, which depends on the redox
center Cys-106 and is modulated by the peripheral cysteine residues.
Impairments of oxidative DJ-1 activation might contribute to the pathogenesis
of PD. 相似文献
6.
7.
8.
Nicholas C. Zitomer Trevor Mitchell Kenneth A. Voss Genevieve S. Bondy Sarah T. Pruett Ethel C. Garnier-Amblard Lanny S. Liebeskind Hyejung Park Elaine Wang M. Cameron Sullards Alfred H. Merrill Jr. Ronald T. Riley 《The Journal of biological chemistry》2009,284(8):4786-4795
Fumonisin B1 (FB1) is a mycotoxin that inhibits
ceramide synthases (CerS) and causes kidney and liver toxicity and other
disease. Inhibition of CerS by FB1 increases sphinganine (Sa), Sa
1-phosphate, and a previously unidentified metabolite. Analysis of the latter
by quadrupole-time-of-flight mass spectrometry assigned an
m/z = 286.3123 in positive ionization mode, consistent with
the molecular formula for deoxysphinganine (C18H40NO).
Comparison with a synthetic standard using liquid chromatography, electrospray
tandem mass spectrometry identified the metabolite as 1-deoxysphinganine
(1-deoxySa) based on LC mobility and production of a distinctive fragment ion
(m/z 44, CH3CH=NH +2) upon
collision-induced dissociation. This novel sphingoid base arises from
condensation of alanine with palmitoyl-CoA via serine palmitoyltransferase
(SPT), as indicated by incorporation of l-[U-13C]alanine
into 1-deoxySa by Vero cells; inhibition of its production in
LLC-PK1 cells by myriocin, an SPT inhibitor; and the absence of
incorporation of [U-13C]palmitate into 1-[13C]deoxySa in
LY-B cells, which lack SPT activity. LY-B-LCB1 cells, in which SPT has been
restored by stable transfection, however, produce large amounts of
1-[13C]deoxySa. 1-DeoxySa was elevated in FB1-treated
cells and mouse liver and kidney, and its cytotoxicity was greater than or
equal to that of Sa for LLC-PK1 and DU-145 cells. Therefore, this
compound is likely to contribute to pathologies associated with fumonisins. In
the absence of FB1, substantial amounts of 1-deoxySa are made and
acylated to N-acyl-1-deoxySa (i.e. 1-deoxydihydroceramides).
Thus, these compounds are an underappreciated category of bioactive sphingoid
bases and “ceramides” that might play important roles in cell
regulation.Fumonisins (FB)2
cause diseases of horses, swine, and other farm animals and are regarded to be
potential risk factors for human esophageal cancer
(1) and, more recently, birth
defects (2). Studies of this
family of mycotoxins, and particularly of the highly prevalent subspecies
fumonisin B1 (FB1) (reviewed in Refs.
1 and
2), have established that
FB1, is both toxic and carcinogenic for laboratory animals, with
the liver and kidney being the most sensitive target organs
(3,
4). Other FB are also toxic,
but their carcinogenicity is unknown.FB are potent inhibitors of ceramide synthase(s) (CerS)
(5), the enzymes responsible
for acylation of sphingoid bases using fatty acyl-CoA for sphingolipid
biosynthesis de novo and recycling pathways
(6). As a consequence of this
inhibition, the substrates sphinganine (Sa) and, usually to a lesser extent,
sphingosine (So), accumulate and are often diverted to sphinganine 1-phosphate
(Sa1P) and sphingosine 1-phosphate (S1P), respectively
(7), while the product
N-acylsphinganines (dihydroceramides), N-acylsphingosines
(ceramides, Cer), and more complex sphingolipids decrease
(5,
7). This disruption of
sphingolipid metabolism has been proposed to be responsible for the toxicity,
and possibly carcinogenicity, of FB, based on mechanistic studies with cells
in culture (5,
7–9).
This has been borne out by a number of animal feeding studies that have
correlated the elevation of Sa in blood, urine, liver, and kidney with liver
and kidney toxicity (4,
7,
10,
11).Most of the mechanistic studies have focused on the accumulation of free Sa
and other sphingoid bases, because these compounds are highly cytotoxic,
although the large number of bioactive metabolites in this pathway make it
likely that multiple mediators may participate
(7,
9). Nonetheless, inhibition of
serine palmitoyltransferase (SPT), the initial enzyme of de novo
sphingolipid biosynthesis, reverses the increased apoptosis and altered cell
growth induced by FB1 treatment
(12–19).
Therefore, it is likely that these effects of FB1 are due to the
accumulation of cytotoxic intermediate(s) rather than depletion of downstream
metabolites, because the latter also occurs when SPT is inhibited.In studies of the effects of FB1 on the renal cell line
LLC-PK1
(20),3
we have noted that in addition to the elevation of Sa and So, there is a large
increase in an unidentified species that appears to be a sphingoid base,
because it is extracted by organic solvents, derivatized with
ortho-phthalaldehyde (OPA), and eluted from reverse-phase liquid
chromatography (LC) in the sphingoid base region. Herein we report: (i) the
isolation and characterization of this novel sphingoid base as
1-deoxysphinganine (1-deoxySa); (ii) that its origin is the utilization of
alanine instead of serine by SPT as well as that the
N-acyl-derivatives of 1-deoxySa (1-deoxydihydroceramides
(1-deoxyDHCer)) are normally found in mammalian cells; (iii) that 1-deoxySa
has cytotoxicity comparable to other sphingoid bases elevated by
FB1; and (iv) that 1-deoxySa is not only elevated in cells in
culture but also in tissues of animals exposed to dietary FB and, therefore,
might contribute to diseases caused by these mycotoxins. 相似文献
9.
DNA damage response (DDR) leads to DNA repair, and depending on the extent of the
damage, to further events, including cell death. Evidence suggests that cell
differentiation may also be a consequence of the DDR. During the formation of
the infective hypha in the phytopathogenic fungus Ustilago
maydis, two DDR kinases, Atr1 and Chk1, are required to induce a G2
cell cycle arrest, which in turn is essential to display the virulence program.
However, the triggering factor of DDR in this process has remained elusive. In
this report we provide data suggesting that no DNA damage is associated with the
activation of the DDR during the formation of the infective filament in
U. maydis. We have analyzed bulk DNA
replication during the formation of the infective filament, and we found no
signs of impaired DNA replication. Furthermore, using RPA-GFP fusion as a
surrogate marker of the presence of DNA damage, we were unable to detect any
sign of DNA damage at the cellular level. In addition, neither MRN nor 9-1-1
complexes, both instrumental to transmit the DNA damage signal, are required for
the induction of the above mentioned cell cycle arrest, as well as for
virulence. In contrast, we have found that the claspin-like protein Mrc1, which
in other systems serves as scaffold for Atr1 and Chk1, was required for both
processes. We discuss possible alternative ways to trigger the DDR, independent
of DNA damage, in U. maydis during virulence
program activation. 相似文献
10.
Ivana I. Knezevic Sanda A. Predescu Radu F. Neamu Matvey S. Gorovoy Nebojsa M. Knezevic Cordus Easington Asrar B. Malik Dan N. Predescu 《The Journal of biological chemistry》2009,284(8):5381-5394
It is known that platelet-activating factor (PAF) induces severe
endothelial barrier leakiness, but the signaling mechanisms remain unclear.
Here, using a wide range of biochemical and morphological approaches applied
in both mouse models and cultured endothelial cells, we addressed the
mechanisms of PAF-induced disruption of interendothelial junctions (IEJs) and
of increased endothelial permeability. The formation of interendothelial gaps
filled with filopodia and lamellipodia is the cellular event responsible for
the disruption of endothelial barrier. We observed that PAF ligation of its
receptor induced the activation of the Rho GTPase Rac1. Following PAF
exposure, both Rac1 and its guanine nucleotide exchange factor Tiam1 were
found associated with a membrane fraction from which they
co-immunoprecipitated with PAF receptor. In the same time frame with
Tiam1-Rac1 translocation, the junctional proteins ZO-1 and VE-cadherin were
relocated from the IEJs, and formation of numerous interendothelial gaps was
recorded. Notably, the response was independent of myosin light chain
phosphorylation and thus distinct from other mediators, such as histamine and
thrombin. The changes in actin status are driven by the PAF-induced localized
actin polymerization as a consequence of Rac1 translocation and activation.
Tiam1 was required for the activation of Rac1, actin polymerization,
relocation of junctional associated proteins, and disruption of IEJs. Thus,
PAF-induced IEJ disruption and increased endothelial permeability requires the
activation of a Tiam1-Rac1 signaling module, suggesting a novel therapeutic
target against increased vascular permeability associated with inflammatory
diseases.The endothelial barrier is made up of endothelial cells
(ECs)4 connected to
each other by interendothelial junctions (IEJs) consisting of protein
complexes organized as tight junctions (TJs) and adherens junctions (AJs). In
addition, the focal adhesion complex located at the basal plasma membrane
enables firm contact of ECs with the underlying basement membrane and also
contributes to the barrier function
(1-3).
The glycocalyx, the endothelial monolayer, and the basement membrane all
together constitute the vascular barrier.The structural integrity of the ECs along with their proper functionality
are the two most important factors controlling the tightness of the
endothelial barrier. Changes affecting these factors cause loss of barrier
restrictiveness and leakiness. Therefore, defining and understanding the
cellular and molecular mechanisms controlling these processes is of paramount
importance. Increased width of IEJs in response to permeability-increasing
mediators (4) regulates the
magnitude of transendothelial exchange of fluid and solutes. Disruption of
IEJs and the resultant barrier leakiness contribute to the genesis of diverse
pathological conditions, such as inflammation
(5), metastasis
(6,
7), and uncontrolled
angiogenesis (8,
9).Accumulated evidence demonstrated that IEJs changes are responsible for
increased or decreased vascular permeability, and the generally accepted
mechanism responsible for them was the myosin light chain (MLC)-mediated
contraction of ECs (5,
10). However, published
evidence showed that an increase in vascular permeability could be obtained
without a direct involvement of any contractile mechanism
(11-16).The main component of the vascular barrier, the ECs, has more than 10% of
their total protein represented by actin
(17), which under
physiological salt concentrations subsists as monomers (G-actin) and assembled
into filaments (F-actin). A large number of actin-interacting proteins may
modulate the assembly, disassembly, and organization of G-actin and of actin
filaments within a given cell type. Similar to the complexity of
actin-interacting proteins found in other cell types, the ECs utilize their
actin binding proteins to stabilize the endothelial monolayer in order to
efficiently function as a selective barrier
(11). In undisturbed ECs, the
actin microfilaments are organized as different networks with distinctive
functional and morphological characteristics: the peripheral filaments also
known as peripheral dense band (PDB), the cytoplasmic fibers identified as
stress fibers (SF), and the actin from the membrane cytoskeleton
(18). The peripheral web,
localized immediately under the membrane, is associated with (i) the luminal
plasmalemma (on the apical side), (ii) the IEJ complexes on the lateral
surfaces, and (iii) the focal adhesion complexes on the abluminal side (the
basal part) of polarized ECs. The SF reside inside the endothelial cytoplasm
and are believed to be directly connected with the plasmalemma proper on the
luminal as well as on the abluminal side of the cell. As described, the
endothelial actin cytoskeleton (specifically the SF) seems to be a stable
structure helping the cells to remain flat under flow
(19). It is also established
that the actin fibers participate in correct localization of different
junctional complexes while keeping them in place
(20). However, it was
suggested that the dynamic equilibrium between F- and G-actin might modulate
the tightness of endothelial barrier in response to different challenges
(13).Mediators effective at nanomolar concentrations or less that disrupt the
endothelial barrier and increase vascular permeability include C2 toxin of
Clostridium botulinum, vascular permeability factor, better known as
vascular endothelial growth factor, and PAF
(21). C2 toxin increases
endothelial permeability by ribosylating monomeric G-actin at Arg-177
(22). This results in the
impairment of actin polymerization
(23), followed by rounding of
ECs (16) and the disruption of
junctional integrity. Vascular permeability factor was shown to open IEJs by
redistribution of junctional proteins
(24,
25) and by interfering with
the equilibrium of actin pools
(26). PAF
(1-O-alkyl-2-acetyl-sn-glycero-3-phosphocoline), a naturally
synthesized phospholipid is active at 10-10 m or less
(27). PAF is synthesized by
and acts on a variety of cell types, including platelets
(28), neutrophils
(29), monocytes
(30), and ECs
(31). PAF-mediated activation
of ECs induced cell migration
(32), angiogenesis
(7), and vascular
hyperpermeability (33)
secondary to disassembly of IEJs
(34). The effects of PAF on
the endothelium are initiated through a G protein-coupled receptor (PAF-R)
localized at the plasmalemma, in a large endosomal compartment inside the cell
(34), and also in the nuclear
membrane (35). In ECs, PAF-R
was shown to signal through Gαq and downstream activation of
phospholipase C isozymes (PLCβ3 and PLCγ1),
and via cSrc (32,
36). Studies have shown that
PAF challenge induced endothelial actin cytoskeletal rearrangement
(37) and marked vascular
leakiness (38); however, the
signaling pathways have not been elucidated.Therefore, in the present study, we carried out a systematic analysis of
PAF-induced morphological and biochemical changes of endothelial barrier
in vivo and in cultured ECs. We found that the opening of endothelial
barrier and the increased vascular leakiness induced by PAF are the result of
a shift in actin pools without involvement of EC contraction, followed by a
redistribution of tight junctional associated protein ZO-1 and adherens
junctional protein VE-cadherin. 相似文献
11.
Soybean Lipoxygenase-1 Oxidizes 3Z-Nonenal
: A Route to
4S-Hydroperoxy-2E-Nonenal and Related
Products
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In previous work with soybean (Glycine max), it was reported that the initial product of 3Z-nonenal (NON) oxidation is 4-hydroperoxy-2E-nonenal (4-HPNE). 4-HPNE can be converted to 4-hydroxy-2E-nonenal by a hydroperoxide-dependent peroxygenase. In the present work we have attempted to purify the 4-HPNE-producing oxygenase from soybean seed. Chromatography on various supports had shown that O2 uptake with NON substrate consistently coincided with lipoxygenase (LOX)-1 activity. Compared with oxidation of LOX's preferred substrate, linoleic acid, the activity with NON was about 400- to 1000-fold less. Rather than obtaining the expected 4-HPNE, 4-oxo-2E-nonenal was the principal product of NON oxidation, presumably arising from the enzyme-generated alkoxyl radical of 4-HPNE. In further work a precipitous drop in activity was noted upon dilution of LOX-1 concentration; however, activity could be enhanced by spiking the reaction with 13S-hydroperoxy-9Z,11E-octadecadienoic acid. Under these conditions the principal product of NON oxidation shifted to the expected 4-HPNE. 4-HPNE was demonstrated to be 83% of the 4S-hydroperoxy-stereoisomer. Therefore, LOX-1 is also a 3Z-alkenal oxygenase, and it exerts the same stereospecificity of oxidation as it does with polyunsaturated fatty acids. Two other LOX isozymes of soybean seed were also found to oxidize NON to 4-HPNE with an excess of 4S-hydroperoxy-stereoisomer. 相似文献
12.
13.
Interaction of Cryptochrome 1, Phytochrome, and Ion Fluxes in
Blue-Light-Induced Shrinking of Arabidopsis
Hypocotyl
Protoplasts 总被引:6,自引:1,他引:5
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Protoplasts isolated from red-light-adapted Arabidopsis hypocotyls and incubated under red light exhibited rapid and transient shrinking within a period of 20 min in response to a blue-light pulse and following the onset of continuous blue light. Long-persisting shrinkage was also observed during continuous stimulation. Protoplasts from a hy4 mutant and the phytochrome-deficient phyA/phyB double mutant of Arabidopsis showed little response, whereas those from phyA and phyB mutants showed a partial response. It is concluded that the shrinking response itself is mediated by the HY4 gene product, cryptochrome 1, whereas the blue-light responsiveness is strictly controlled by phytochromes A and B, with a greater contribution by phytochrome B. It is shown further that the far-red-absorbing form of phytochrome (Pfr) was not required during or after, but was required before blue-light perception. Furthermore, a component that directly determines the blue-light responsiveness was generated by Pfr after a lag of 15 min over a 15-min period and decayed with similar kinetics after removal of Pfr by far-red light. The anion-channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoic acid prevented the shrinking response. This result, together with those in the literature and the kinetic features of shrinking, suggests that anion channels are activated first, and outward-rectifying cation channels are subsequently activated, resulting in continued net effluxes of Cl− and K+. The postshrinking volume recovery is achieved by K+ and Cl− influxes, with contribution by the proton motive force. External Ca2+ has no role in shrinking and the recovery. The gradual swelling of protoplasts that prevails under background red light is shown to be a phytochrome-mediated response in which phytochrome A contributes more than phytochrome B. 相似文献
14.
Tiane Martin de Moura Ana Paula Vaz Cassenego Fabrício Souza Campos Andrea Machado Leal Ribeiro Ana Cláudia Franco Pedro Alves d'Azevedo Jeverson Frazzon Ana Paula Guedes Frazzon 《Memórias do Instituto Oswaldo Cruz》2013,108(4):453-456
Here we report the presence and expression levels of the vanC
1 and vanC 2/3 genes in vancomycin-susceptible strains of Enterococcus
faecalis. The vanC 1 and vanC 2/3 genes were located in the plasmid DNA and on the chromosome,
respectively. Specific mRNA of the vanC 1 gene was detected in one of these strains. Additionally, analysis of
the vanC gene sequences showed that these genes are related to
the vanC genes of Enterococcus gallinarum and
Enterococcus casseliflavus. The presence of
vanC genes is useful for the identification of E.
gallinarum and E. casseliflavus. Moreover, this is
the first report of vanC mRNA in E.
faecalis. 相似文献
15.
Farah H. Bardai Valerie Price Marcus Zaayman Lulu Wang Santosh R. D'Mello 《The Journal of biological chemistry》2012,287(42):35444-35453
Both neuroprotective and neurotoxic roles have previously been described for histone deacetylase-1 (HDAC1). Here we report that HDAC1 expression is elevated in vulnerable brain regions of two mouse models of neurodegeneration, the R6/2 model of Huntington disease and the Ca2+/calmodulin-dependent protein kinase (CaMK)/p25 double-transgenic model of tauopathic degeneration, suggesting a role in promoting neuronal death. Indeed, elevating HDAC1 expression by ectopic expression promotes the death of otherwise healthy cerebellar granule neurons and cortical neurons in culture. The neurotoxic effect of HDAC1 requires interaction and cooperation with HDAC3, which has previously been shown to selectively induce the death of neurons. HDAC1-HDAC3 interaction is greatly elevated under conditions of neurodegeneration both in vitro and in vivo. Furthermore, the knockdown of HDAC3 suppresses HDAC1-induced neurotoxicity, and the knockdown of HDAC1 suppresses HDAC3 neurotoxicity. As described previously for HDAC3, the neurotoxic effect of HDAC1 is inhibited by treatment with IGF-1, the expression of Akt, or the inhibition of glycogen synthase kinase 3β (GSK3β). In addition to HDAC3, HDAC1 has been shown to interact with histone deacetylase-related protein (HDRP), a truncated form of HDAC9, whose expression is down-regulated during neuronal death. In contrast to HDAC3, the interaction between HDRP and HDAC1 protects neurons from death, an effect involving acquisition of the deacetylase activity of HDAC1 by HDRP. We find that elevated HDRP inhibits HDAC1-HDAC3 interaction and prevents the neurotoxic effect of either of these two proteins. Together, our results suggest that HDAC1 is a molecular switch between neuronal survival and death. Its interaction with HDRP promotes neuronal survival, whereas interaction with HDAC3 results in neuronal death. 相似文献
16.
17.
In the current study, we tested the in vivo effects of Yy1 gene dosage on the Peg3 imprinted domain with various breeding schemes utilizing two sets of mutant alleles. The results indicated that a half dosage of Yy1 coincides with the up-regulation of Peg3 and Zim1, suggesting a repressor role of Yy1 in this imprinted domain. This repressor role of Yy1 is consistent with the observations derived from previous in vitro studies. The current study also provided an unexpected observation that the maternal allele of Peg3 is also normally expressed, and thus the expression of Peg3 is bi-allelic in the specific areas of the brain, including the choroid plexus, the PVN (Paraventricular Nucleus) and the SON (Supraoptic Nucleus) of the hypothalamus. The exact roles of the maternal allele of Peg3 in these cell types are currently unknown, but this new finding confirms the previous prediction that the maternal allele may be functional in specific cell types based on the lethality associated with the homozygotes for several mutant alleles of the Peg3 locus. Overall, these results confirm the repressor role of Yy1 in the Peg3 domain and also provide a new insight regarding the bi-allelic expression of Peg3 in mouse brain. 相似文献
18.
Wanfen Xiong Rebecca Knispel Jason MacTaggart Timothy C. Greiner Stephen J. Weiss B. Timothy Baxter 《The Journal of biological chemistry》2009,284(3):1765-1771
During arterial aneurysm formation, levels of the membrane-anchored matrix
metalloproteinase, MT1-MMP, are elevated dramatically. Although MT1-MMP is
expressed predominately by infiltrating macrophages, the roles played by the
proteinase in abdominal aortic aneurysm (AAA) formation in vivo
remain undefined. Using a newly developed chimeric mouse model of AAA, we now
demonstrate that macrophage-derived MT1-MMP plays a dominant role in disease
progression. In wild-type mice transplanted with MT1-MMP-null marrow, aneurysm
formation induced by the application of CaCl2 to the aortic surface
was almost completely ablated. Macrophage infiltration into the aortic media
was unaffected by MT1-MMP deletion, and AAA formation could be reconstituted
when MT1-MMP+/+ macrophages, but not MT1-MMP+/+
lymphocytes, were infused into MT1-MMP-null marrow recipients. In
vitro studies using macrophages isolated from either
WT/MT1-MMP-/- chimeric mice, MMP-2-null mice, or MMP-9-null mice
demonstrate that MT1-MMP alone plays a dominant role in macrophage-mediated
elastolysis. These studies demonstrate that destruction of the elastin fiber
network during AAA formation is dependent on macrophage-derived MT1-MMP, which
unexpectedly serves as a direct-acting regulator of macrophage proteolytic
activity.Development and progression of abdominal aortic aneurysm
(AAA)2 is a complex
process that, untreated, can lead to tissue failure, hemorrhage, and death
(1). Destruction of the orderly
elastin lamellae of the vessel wall is considered the sine qui non of arterial
aneurysm formation (2) as adult
tissues cannot regenerate normal elastin fibers
(3). Moreover, the elastin
degradation products are chemotactic for inflammatory cells and serve to
amplify the local injury (4).
Although several types of elastolytic proteases are elevated in AAA tissue
(5-9),
studies using murine models of AAA and targeted protease deletion suggest that
matrix metalloproteinases (MMPs), particularly the secreted proteases, MMP-2
and MMP-9, play key roles in the pathologic remodeling of the elastin lamellae
that lead to AAA (7,
8).Membrane-type 1 MMP (MT1-MMP) is the prototypical member of a family of
membrane-tethered MMPs (10).
Recent studies indicate that MT1-MMP expression is elevated in human AAA
tissues and that infiltrating macrophages are the primary source of the
proteinase in aortic lesions
(11-13).
Although indirect evidence suggests that MT1-MMP may participate in the
control of monocyte/macrophage motile responses as well as interactions with
the vessel wall during transmigration
(14,
15), the role(s) played by
MT1-MMP in regulating macrophage proteolytic activity or AAA formation in
vivo remains undefined.Using a murine model of AAA and mice with a targeted deletion of MT1-MMP in
myelogenous cell populations, we now demonstrate that macrophage-derived
MT1-MMP is required for elastin degradation and aneurysm formation.
Importantly, macrophages are not dependent on MT1-MMP for infiltrating aortic
tissues but instead use the protease to directly regulate their elastolytic
potential in an MMP-2- and MMP-9-independent fashion. These studies define a
new and unexpected role for MT1-MMP in controlling macrophage elastolytic
activity in the in vitro and in vivo settings. 相似文献
19.
Nitrogen is one of the most important limiting factors for plant growth. However, as ammonium is readily converted into ammonia (NH3) when soil pH rises above 8.0, this activity depletes the availability of ammonium (NH4
+) in alkaline soils, consequently preventing the growth of most plant species. The perennial wild grass Puccinellia tenuiflora is one of a few plants able to grow in soils with extremely high salt and alkaline pH (>9.0) levels. Here, we assessed how this species responds to ammonium under such conditions by isolating and analyzing the functions of a putative ammonium transporter (PutAMT1;1). PutAMT1;1 is the first member of the AMT1 (ammonium transporter) family that has been identified in P. tenuiflora. This gene (1) functionally complemented a yeast mutant deficient in ammonium uptake (2), is preferentially expressed in the anther of P. tenuiflora, and (3) is significantly upregulated by ammonium ions in both the shoot and roots. The PutAMT1;1 protein is localized in the plasma membrane and around the nuclear periphery in yeast cells and P. tenuiflora suspension cells. Immunoelectron microscopy analysis also indicated that PutAMT1;1 is localized in the endomembrane. The overexpression of PutAMT1;1 in A. thaliana enhanced plant growth, and increased plant susceptibility to toxic methylammonium (MeA). Here, we confirmed that PutAMT1;1 is an ammonium-inducible ammonium transporter in P. tenuiflora. On the basis of the results of PutAMT1;1 overexpression in A. thaliana, this gene might be useful for improving the root to shoot mobilization of MeA (or NH4
+). 相似文献
20.
Claire Amiable Sylvie Pochet André Padilla Gilles Labesse Pierre Alexandre Kaminski 《PloS one》2013,8(11)
The gene dnph1 (or rcl) encodes a hydrolase that cleaves the 2’-deoxyribonucleoside 5’-monophosphate (dNMP) N-glycosidic bond to yield a free nucleobase and 2-deoxyribose 5-phosphate. Recently, the crystal structure of rat DNPH1, a potential target for anti-cancer therapies, suggested that various analogs of AMP may inhibit this enzyme. From this result, we asked whether N
6-substituted AMPs, and among them, cytotoxic cytokinin riboside 5’-monophosphates, may inhibit DNPH1. Here, we characterized the structural and thermodynamic aspects of the interactions of these various analogs with DNPH1. Our results indicate that DNPH1 is inhibited by cytotoxic cytokinins at concentrations that inhibit cell growth. 相似文献