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Ajit K. Satapathy Donald J. Crampton Benjamin B. Beauchamp Charles C. Richardson 《The Journal of biological chemistry》2009,284(21):14286-14295
The multifunctional protein encoded by gene 4 of bacteriophage T7 (gp4)
provides both helicase and primase activity at the replication fork. T7 DNA
helicase preferentially utilizes dTTP to unwind duplex DNA in vitro
but also hydrolyzes other nucleotides, some of which do not support helicase
activity. Very little is known regarding the architecture of the nucleotide
binding site in determining nucleotide specificity. Crystal structures of the
T7 helicase domain with bound dATP or dTTP identified Arg-363 and Arg-504 as
potential determinants of the specificity for dATP and dTTP. Arg-363 is in
close proximity to the sugar of the bound dATP, whereas Arg-504 makes a
hydrogen bridge with the base of bound dTTP. T7 helicase has a serine at
position 319, whereas bacterial helicases that use rATP have a threonine in
the comparable position. Therefore, in the present study we have examined the
role of these residues (Arg-363, Arg-504, and Ser-319) in determining
nucleotide specificity. Our results show that Arg-363 is responsible for dATP,
dCTP, and dGTP hydrolysis, whereas Arg-504 and Ser-319 confer dTTP
specificity. Helicase-R504A hydrolyzes dCTP far better than wild-type
helicase, and the hydrolysis of dCTP fuels unwinding of DNA. Substitution of
threonine for serine 319 reduces the rate of hydrolysis of dTTP without
affecting the rate of dATP hydrolysis. We propose that different nucleotides
bind to the nucleotide binding site of T7 helicase by an induced fit
mechanism. We also present evidence that T7 helicase uses the energy derived
from the hydrolysis of dATP in addition to dTTP for mediating DNA
unwinding.Helicases are molecular machines that translocate unidirectionally along
single-stranded nucleic acids using the energy derived from nucleotide
hydrolysis
(1–3).
The gene 4 protein encoded by bacteriophage T7 consists of a helicase domain
and a primase domain, located in the C-terminal and N-terminal halves of the
protein, respectively (4). The
T7 helicase functions as a hexamer and has been used as a model to study
ring-shaped replicative helicases. In the presence of dTTP, T7 helicase binds
to single-stranded DNA
(ssDNA)3 as a hexamer
and translocates 5′ to 3′ along the DNA strand using the energy of
hydrolysis of dTTP
(5–7).
T7 helicase hydrolyzes a variety of ribo and deoxyribonucleotides; however,
dTTP hydrolysis is optimally coupled to DNA unwinding
(5).Most hexameric helicases use rATP to fuel translocation and unwind DNA
(3). T7 helicase does hydrolyze
rATP but with a 20-fold higher Km as compared with dTTP
(5,
8). It has been suggested that
T7 helicase actually uses rATP in vivo where the concentration of
rATP is 20-fold that of dTTP in the Escherichia coli cell
(8). However, hydrolysis of
rATP, even at optimal concentrations, is poorly coupled to translocation and
unwinding of DNA (9). Other
ribonucleotides (rCTP, rGTP, and rUTP) are either not hydrolyzed or the poor
hydrolysis observed is not coupled to DNA unwinding
(8). Furthermore, Patel et
al. (10) found that the
form of T7 helicase found in vivo, an equimolar mixture of the
full-length gp4 and a truncated form lacking the zinc binding domain of the
primase, prefers dTTP and dATP. Therefore, in the present study we have
restricted our examination of nucleotides to the deoxyribonucleotides.The nucleotide binding site of the replicative DNA helicases, such as T7
gene 4 protein, bind nucleotides at the subunit interface
(Fig. 1) located between two
RecA-like subdomains that bind ATP
(11,
12). The location of the
nucleotide binding site at the subunit interface provides multiple
interactions of residues with the bound NTP. A number of cis- and
trans-acting amino acids stabilize the bound nucleotide in the
nucleotide binding site and also provide for communication between subunits
(13–15).
Earlier reports revealed that the arginine finger (Arg-522) in T7 helicase is
positioned to interact with the γ-phosphate of the bound nucleotide in
the adjacent subunit (12,
16). However, His-465
(phosphate sensor), Glu-343 (catalytic base), and Asp-424 (Walker motif B)
interacts with the γ-phosphate of the bound nucleotide in the same
subunit (12,
17,
18). The arginine finger and
the phosphate sensor have been proposed to couple NTP hydrolysis to DNA
unwinding. Substitution of Glu-343, the catalytic base, eliminates dTTP
hydrolysis (19), and
substitution of Asp-424 with Asn leads to a severe reduction in dTTP
hydrolysis (20). The conserved
Lys-318 in Walker motif A interacts with the β-phosphate of the bound
nucleotide and plays an important role in dTTP hydrolysis
(21).Open in a separate windowFIGURE 1.Crystal structure of T7 helicase. A, crystal structure of
the hexameric helicase C-terminal domain of gp4
(17). The structure reveals a
ring-shaped molecule with a central core through which ssDNA passes. The
inset shows the interface between two subunits of the helicase with
adenosine 5′-{β,γ-imidol}-triphosphate in the nucleotide
binding site. B, the nucleotide binding site of a monomer of the gp4
with the crucial amino acid residues reported earlier and in the present study
is shown in sticks. The crystal structures of the T7 gene 4 helicase
domain (12) with bound dTTP
(C) and dATP (D). The structures shown are the nucleotide
binding site of T7 helicase as viewed in Pymol by analyzing the PDB files 1cr1
and 1cr2 (12). Arg-504 and
Tyr-535 sandwiches the base of the bound dNTP. Additionally, Arg-504 forms a
hydrogen bridge with dTTP. Arg-363 interacts specifically with the 3-OH group
of bound dATP. AMPPNP, adenosine
5′-(β,γ-imino)triphosphate.Considering the wealth of information on the above residues that are
involved in the hydrolysis of dTTP and the coupling of hydrolysis to
unwinding, it is intriguing that little information is available on nucleotide
specificity. Several crystal structures of T7 helicase in complex with a
nucleotide triphosphate are available. However, most of structures were
crystallized with a non-hydrolyzable analogue of dTTP or the nucleotide was
diffused into the crystal. The crystal structure of the T7 helicase domain
bound with dTTP or dATP was reported by Sawaya et al.
(12). These structures
assisted us in identifying two basic residues (Arg-363 and Arg-504) in close
proximity to the sugar and base of the bound nucleotide whose orientation
suggested that these residues could be involved in nucleotide selection.
Arg-504 together with Tyr-535 sandwich the base of the bound nucleotide at the
subunit interface of the hexameric helicase
(Fig. 1). Arg-504 and Tyr-535
are structurally well conserved in various helicases
(12). However, Arg-504 could
make a hydrogen bridge with the OH group of thymidine, thus suggesting a role
in dTTP specificity. On the other hand, Arg-363 is in close proximity
(∼3.4 Å) to the sugar 3′-OH of bound dATP, whereas in the
dTTP-bound structure this residue is displaced by 7.12 Å
(Fig. 1) from the equivalent
position. Consequently Arg-363 could play a role in dATP binding. The crystal
structures do not provide any information on different interaction of residues
with the phosphates of dATP and dTTP. However, alignment of the residues in
the P-loops of different hexameric helicases reveals that the serine adjacent
to the invariant lysine at position 319 (Ser-319) is conserved in
bacteriophages, whereas bacterial helicases have a conserved threonine in the
equivalent position (supplemental Fig. 1). Bacterial helicases use rATP in the
DNA unwinding reactions. whereas T7 helicase preferentially uses dTTP, and
bacteriophage T4 gene 41 uses rGTP or rATP
(22).Although considerable information is available on the role of residues in
nucleotide binding and dTTP hydrolysis, very little is known on the
determinants of nucleotide specificity. In the present study we made an
attempt to address the role of a few selected residues (Arg-363, Arg-504, and
Ser-319) in determining nucleotide specificity, especially dTTP and dATP, both
of which are hydrolyzed and mediate DNA unwinding. We show that under
physiological conditions T7 helicase uses the energy derived from the
hydrolysis of dATP in addition to dTTP for mediating DNA unwinding. 相似文献
4.
Nidhi Ahuja Dmitry Korkin Rachna Chaba Brent O. Cezairliyan Robert T. Sauer Kyeong Kyu Kim Carol A. Gross 《The Journal of biological chemistry》2009,284(8):5403-5413
The Escherichia coli envelope stress response is controlled by the
alternative sigma factor, σE, and is induced when unfolded
outer membrane proteins accumulate in the periplasm. The response is initiated
by sequential cleavage of the membrane-spanning antisigma factor, RseA. RseB
is an important negative regulator of envelope stress response that exerts its
negative effects onσE activity through its binding to RseA.
In this study, we analyze the interaction between RseA and RseB. We found that
tight binding of RseB to RseA required intact RseB. Using programs that
performed global and local sequence alignment of RseB and RseA, we found
regions of high similarity and performed alanine substitution mutagenesis to
test the hypothesis that these regions were functionally important. This
protocol is based on the hypothesis that functionally dependent regions of two
proteins co-evolve and therefore are likely to be sequentially conserved. This
procedure allowed us to identify both an N-terminal and C-terminal region in
RseB important for binding to RseA. We extensively analyzed the C-terminal
region, which aligns with a region of RseA coincident with the major RseB
binding determinant in RseA. Both allele-specific suppression analysis and
cysteine-mediated disulfide bond formation indicated that this C-terminal
region of similarity of RseA and RseB identifies a contact site between the
two proteins. We suggest a similar protocol can be successfully applied to
pairs of non-homologous but functionally linked proteins to find specific
regions of the protein sequences that are important for establishing
functional linkage.The Escherichia coli σE-mediated envelope stress
response is the major pathway to ensure homeostasis in the envelope
compartment of the cell
(1-3).
σE regulon members encode periplasmic chaperones and
proteases, the machinery for inserting β-barrel proteins into the outer
membrane and components controlling the synthesis and assembly of LPS
(4-6).
This pathway is highly conserved among γ-proteobacteria
(6).The σE response is initiated when periplasmic protein
folding and assembly is compromised
(7-9).
During steady state growth, σE is inhibited by its antisigma
factor, RseA, a membrane-spanning protein whose cytoplasmic domain binds to
σE with picomolar affinity
(10-13).
Accumulation of unassembled porin monomers serves as a signal to activate the
DegS protease to cleave RseA in its periplasmic domain
(14,
15). This initiates a
proteolytic cascade in which RseP cleaves periplasmically truncated RseA near
or within the cytoplasmic membrane to release the
RseAcytoplasmic-σE complex, and cytoplasmic
ATP-dependent proteases complete the degradation of RseA thereby releasing
active σE
(16-19).RseB, a second negative regulator of the envelope stress response
(11,
20,
21), binds to the periplasmic
domain of RseA with nanomolar affinity. RseB is an important regulator of the
response (2,
22,
23). It prevents RseP from
degrading intact RseA, thereby ensuring that proteolysis is initiated only
when the DegS protease is activated by a stress signal
(21). Additionally, RseB
prevents activated DegS from cleaving RseA, suggesting that interaction of
RseB with RseA must be altered before the signal transduction cascade is
activated (23).The goal of the present studies was to explore how RseB binds to RseA. The
interaction partner of RseB is the unstructured periplasmic domain of RseA
(RseA-peri). Within RseA-peri, amino acids ∼169-186 constitute a major
binding determinant to RseB
(23,
24). This peptide alone binds
RseB with 6 μm affinity, and deleting this region abrogates
binding to RseB (23).
Additional regions of RseA-peri also contribute to RseB binding, as intact
RseA-peri binds with 20 nm affinity to RseB
(23). Much less is known about
the regions of RseB required for interaction with RseA. RseB is homodimeric
two-domain protein, whose large N-terminal domain shares structural homology
with LolA, a protein that transports lipoproteins to outer membrane
(24,
25). The smaller C-terminal
domain is connected to the N-terminal domain by a linker, and the two domains
share a large interface, which may facilitate interdomain signaling.
Glutaraldehyde cross-linking studies indicate that the C-terminal domain
interacts with RseA, but the regions of interaction were not identified
(25).In the present report, we study the interaction of RseB and RseA. We
establish that both domains of RseB interact with RseA-peri. Using a global
sequence alignment, we discovered several regions in RseA and RseB that had
high sequence similarity, despite the low overall sequence similarity between
these two proteins, a finding that was independently confirmed by a local
sequence similarity algorithm. This suggested that these regions were
functionally dependent, and we performed a set of mutagenesis experiments
designed to test this idea. Our studies of the binding properties of these
mutants revealed that regions in both the N terminus and C terminus of RseB
modulate interaction with RseA. Moreover, genetic suppression analysis and
cysteine-mediated disulfide bond formation suggest that the region of RseA/B
with highest similarity (RseA residues 165-191 (major binding determinant in
RseA) and RseB residues 233-258) are interacting partners. 相似文献
5.
Thor Veen M?rten B. Hjernquist Steven L. Van Wilgenburg Keith A. Hobson Eelke Folmer Laura Font Marcel Klaassen 《PloS one》2014,9(5)
Migratory routes and wintering grounds can have important fitness consequences, which can lead to divergent selection on populations or taxa differing in their migratory itinerary. Collared (Ficedula albicollis) and pied (F. hypoleuca) flycatchers breeding in Europe and wintering in different sub-Saharan regions have distinct migratory routes on the eastern and western sides of the Sahara desert, respectively. In an earlier paper, we showed that hybrids of the two species did not incur reduced winter survival, which would be expected if their migration strategy had been a mix of the parent species'' strategies potentially resulting in an intermediate route crossing the Sahara desert to different wintering grounds. Previously, we compared isotope ratios and found no significant difference in stable-nitrogen isotope ratios (δ
15N) in winter-grown feathers between the parental species and hybrids, but stable-carbon isotope ratios (δ
13C) in hybrids significantly clustered only with those of pied flycatchers. We followed up on these findings and additionally analyzed the same feathers for stable-hydrogen isotope ratios (δ
2H) and conducted spatially explicit multi-isotope assignment analyses. The assignment results overlapped with presumed wintering ranges of the two species, highlighting the efficacy of the method. In contrast to earlier findings, hybrids clustered with both parental species, though most strongly with pied flycatcher. 相似文献
6.
Rogério Bertani 《ZooKeys》2012,(230):1-94
Three aviculariine genera endemic to Brazil are revised. Typhochlaena C. L. Koch, 1850 is resurrected, including five species; Pachistopelma Pocock, 1901 includes two species; and Iridopelma Pocock, 1901, six species. Nine species are newly described: Typhochlaena amma
sp. n., Typhochlaena costae
sp. n., Typhochlaena curumim
sp. n., Typhochlaena paschoali
sp. n., Pachistopelma bromelicola
sp. n., Iridopelma katiae
sp. n., Iridopelma marcoi
sp. n., Iridopelma oliveirai
sp. n. and Iridopelma vanini
sp. n. Three new synonymies are established: Avicularia pulchra Mello-Leitão, 1933 and Avicularia recifiensis Struchen & Brändle, 1996 are junior synonyms of Pachistopelma rufonigrum Pocock, 1901 syn. n., and Avicularia palmicola Mello-Leitão, 1945 is a junior synonym of Iridopelma hirsutum Pocock, 1901 syn. n.
Pachistopelma concolor Caporiacco, 1947 is transferred to Tapinauchenius Ausserer, 1871, making the new combination Tapinauchenius concolor (Caporiacco, 1947)
comb. n. Lectotypes are newly designed for Pachistopelma rufonigrum Pocock, 1901 , Iridopelma hirsutum Pocock, 1901 and Pachistopelma concolor Caporiacco, 1947. Cladistic analyses using both equal and implied weights were carried out with a matrix comprising 62 characters and 38 terminal taxa. The chosen cladogram found with X-Pee-Wee and concavity 6 suggests they are monophyletic. All species are keyed and mapped and information on species habitat and area cladograms are presented. Discussion on biogeography and conservation is provided. 相似文献
7.
Hsiu-Fang Fan 《Biophysical journal》2009,96(5):1875-1883
Escherichia coli RecBCD helicase unwinds blunt-end duplex DNA to repair damaged DNA molecules in the homologous recombination pathway. Previous single-molecule experiments showed that RecBCD recognizes an 8 nt DNA sequence, χ, and lowers its unwinding rate afterward under saturating ATP condition. We have developed a single-molecule force-tethered particle motion (FTPM) method, which is modified from the conventional TPM method, and applied it to study RecBCD motion in detail. In the FTPM experiment, a stretching force is applied to the DNA-bead complex that suppresses the bead's Brownian motion, resulting in an improved spatial resolution at long DNA substrates. Based on the equipartition theorem, the mean-square displacement of the bead's Brownian motion measured by FTPM correlates linearly to DNA extension length with a predicted slope, circumventing the difficulties of conventional TPM experiments, such as nonlinearity and low resolution of long DNA substrates. The FTPM method offers the best resolution in the presence of only a small stretching force (0.20 pN). We used the FTPM method to investigate RecBCD helicase motion along 4.1 kb long χ-containing duplex DNA molecules, and observed that the translocation rate of RecBCD changes after the χ sequence under limited ATP concentrations. This suggests that χ recognition by RecBCD does not require saturating ATP conditions, contrary to what was previously reported. 相似文献
8.
To the memory of William Ronald Sendall
Sternaspid polychaetes are common and often abundant in soft bottoms in the world oceans. Some authors suggest that only one species should be recognized, whereas others regard a few species as widely distributed in many seas and variable depths from the low intertidal to about 4400 m. There are some problems with species delineation and the distinctive ventro-caudal shield has been disregarded or barely used for identifying species. In order to clarify these issues, the ventral shield is evaluated in specimens from the same locality and its diagnostic potential is confirmed. On this basis, a revision of Sternaspis Otto, 1821 (Polychaeta: Sternaspidae) is presented based upon type materials, or material collected from type localities. The sternaspid body, introvert hooks and shield show three distinct patterns, two genera have seven abdominal segments and tapered introvert hooks, and one genus has eight abdominal segments and spatulate introvert hooks. The ventro-caudal shield has three different patterns: stiff with ribs, and sometimes concentric lines, stiff with feebly-defined ribs but no concentric lines, and soft with firmly adhered sediment particles. Sternaspis is restricted to include species with seven abdominal segments, falcate introvert hooks, and stiff shields, often exhibiting radial ribs, concentric lines or both. Sternaspis includes, besides the type species, Sternaspis thalassemoides Otto, 1821 from the Mediterranean Sea, Sternaspis affinis Stimpson, 1864 from the Northeastern Pacific, Sternaspis africana Augener, 1918, stat. n. from Western Africa, Sternaspis andamanensis
sp. n. from the Andaman Sea, Sternaspis costata von Marenzeller, 1879 from Japan, Sternaspis fossor Stimpson, 1853 from the Northwestern Atlantic, Sternaspis islandica Malmgren, 1867 from Iceland, Sternaspis maior Chamberlin, 1919 from the Gulf of California, Sternaspis princeps Selenka, 1885 from New Zealand, Sternaspis rietschi Caullery, 1944 from abyssal depths around Indonesia, Sternaspis scutata (Ranzani, 1817) from the Mediterranean Sea, Sternaspis spinosa Sluiter, 1882 from Indonesia, and Sternaspis thorsoni
sp. n. from the Iranian Gulf. Two genera are newly proposed to incorporate the remaining species: Caulleryaspis and Petersenaspis. Caulleryaspis
gen. n. is defined by the presence of falcate introvert hooks, seven abdominal segments, and soft shields with sediment particles firmly adhered on them; it includes two species: Caulleryaspis gudmundssoni
sp. n. from Iceland and Caulleryaspis laevis (Caullery, 1944) comb. n. from Indonesia. Petersenaspis
gen. n. is defined by the presence of spatulate introvert hooks, eight abdominal segments, and stiff shields with poorly defined ribs but no concentric line; it includes Petersenaspis capillata (Nonato, 1966) from Brazil and Petersenaspis palpallatoci
sp. n. from the Philippines. Neotypes are proposed for eight species: Sternaspis thalassemoides, Sternaspis affinis, Sternaspis africana, Sternaspis costata, Sternaspis fossor, Sternaspis maior, Sternaspis scutata and Sternaspis spinosa, to stabilize these species-group names, and a lectotype is designated for Sternaspis laevis which is transferred to Caulleryaspis
gen. n. The geographic range of most species appears to be much smaller than previously indicated, and for some species additional material in good condition is needed to clarify their distributions. Keys to genera and to all species are also included. 相似文献
9.
10.
11.
Multiple Functions of Nuclear DNA Helicase Ⅱ (RNA Helicase A) in Nucleic Acid Metabolism 总被引:6,自引:0,他引:6
Secondary structures of nucleic acids play an importantrole in regulating their transactions as carriers of thegenetic information, including DNA replication, trans-cription, RNA processing, RNA transport, and translation.Resolving double-stranded (ds) DNA or RNA is usually anenergy-dependent process that can be accomplished byproteins termed DNA or RNA helicases, which are presentin all prokaryotic and eukaryotic organisms. Earlier attemptsto find mammalian helicases led to the detect… 相似文献
12.
Duvalius (sg. Neoduvalius) gejzadunayi
sp. n. from Pećina u Dubokom potoku cave ( Donje Biševo village near Rožaje, Montenegro), the first known representative of this subgenus from the territory of Montenegro is described, illustrated and compared with the related species of the subgenus Neoduvalius Müller, 1913. This new species is characterised by depigmented, medium sized body, totally reduced eyes, deep and complete frontal furrows, 3–4 pairs of discal setae in third elytral stria, as well as by the shape of aedeagus. Data on the distribution and the ecology of this remarkable species, as well as a check-list of the subgenus Neoduvalius are also provided. Recently described genera Serboduvalius Ćurčić, S. B. Pavićević & Ćurčić, B.P.M., 2001, Rascioduvalius Ćurčić, S. B. Brajković, Mitić & Ćurčić, B.P.M., 2003, Javorella Ćurčić, S. B. Brajković, Ćurčić, B.P.M. & Mitić, 2003 and Curcicia Ćurčić, S. B. & Brajković, 2003 are regarded as junior synonyms of the genus Duvalius Delarouzée. 相似文献
13.
Kaliyamurthi Venkatachalam Balachandar Venkatesan Anthony J. Valente Peter C. Melby Sailesh Nandish Jane E. B. Reusch Robert A. Clark Bysani Chandrasekar 《The Journal of biological chemistry》2009,284(21):14414-14427
WNT1-inducible signaling pathway protein-1 (WISP1), a member of the
CYR61/CTGF/Nov family of growth factors, can mediate cell growth,
transformation, and survival. Previously we demonstrated that WISP1 is
up-regulated in post-infarct heart, stimulates cardiac fibroblast
proliferation, and is induced by the proinflammatory cytokine tumor necrosis
factor-α (TNF-α). Here we investigated (i) the localization of
TNF-α and WISP1 in post-infarct heart, (ii) the mechanism of
TNF-α-mediated WISP1 induction in primary human cardiac fibroblasts
(CF), (iii) the role of WISP1 in TNF-α-mediated CF proliferation and
collagen production, and (iv) the effects of WISP1 on TNF-α-mediated
cardiomyocyte death. TNF-α and WISP1 expressions were increased in the
border zones and non-ischemic remote regions of the post-ischemic heart. In
CF, TNF-α potently induced WISP1 expression in cyclic AMP response
element-binding protein (CREB)-dependent manner. TNF-α induced CREB
phosphorylation in vitro and DNA binding and reporter gene activities
in vivo. TNF-α induced CREB activation via ERK1/2, and
inhibition of ERK1/2 and CREB blunted TNF-α-mediated WISP1 induction.
Most importantly, WISP1 knockdown attenuated TNF-α stimulated collagen
production and CF proliferation. Furthermore, WISP1 attenuated
TNF-α-mediated cardiomyocyte death, thus demonstrating pro-mitogenic and
pro-survival effects for WISP1 in myocardial constituent cells. Our results
suggest that a TNF-α/WISP1 signaling pathway may contribute to
post-infarct cardiac remodeling, a condition characterized by fibrosis and
progressive cardiomyocyte loss.Acute myocardial infarction
(MI)2 is a major cause
of morbidity and mortality worldwide. After acute MI, the two principal
determinants of patient outcome are myocardial infarct size and the extent of
left ventricular (LV) remodeling
(1–3).
Infarct size is determined during the acute phase immediately post-MI. LV
remodeling on the other hand is a continuous and maladaptive process
characterized by progressive left ventricular hypertrophy, fibrosis,
ventricular dilatation, and by the gradual deterioration of cardiac
performance, leading ultimately to congestive heart failure
(1–3).Numerically, fibroblasts are the major cell type in the heart, but they
constitute a smaller total volume compared with cardiomyocytes
(4). Fibroblasts are associated
primarily with modulation of extracellular matrix and tissue healing/repair
(4–6).
Fibroblasts secrete collagens, fibrillins, fibronectin, laminin, and matrix
metalloproteinases and, thus, are responsible for the maintenance of
connective tissue homeostasis
(4–7).
We and others have shown that primary cardiac fibroblasts also produce various
cytokines, chemokines, and growth factors
(4–6,
8,
9), which tightly regulate the
physiological function of the cells. Under pathological conditions, however,
where the expression of cytokines and growth factors is significantly altered,
the fibroblasts can undergo differentiation, migration, and proliferation,
resulting in pathological fibrosis because of excessive accumulation of
collagens and other ECM proteins
(4–6).The six members of the CCN (CYR61/CTGF/Nov) family of
growth factors (Cyr61 (cysteine-rich 61, CCN1), CTGF (connective tissue growth
factor, CCN2), Nov (nephroblastoma-overexpressed, CCN3), WISP1 (WNT1-inducible
signaling pathway protein-1, CCN4), WISP2 (CCN5), and WISP3 (CCN6)) are
involved in a number of cellular processes, including adhesion, migration, and
proliferation
(10–12).
Although their roles in angiogenesis and oncogenesis are well characterized,
with the exception of CTGF, their precise contribution to myocardial
remodeling is unknown. Recently we demonstrated that whereas WISP1 is
expressed in the heart at low basal levels, permanent occlusion of the left
anterior descending coronary artery significantly up-regulates its expression
in the non-ischemic myocardium
(13). Furthermore, we have
found that WISP1 exerts both pro-hypertrophic and pro-mitogenic effects in
vitro, stimulating Akt-dependent cardiomyocyte growth, as well as
collagen synthesis and fibroblast proliferation
(13). Because cardiomyocyte
hypertrophy and fibroblast proliferation play central roles in remodeling and
WISP1 regulates these two critical processes, it is plausible that WISP1 also
mediates cardiac remodeling after myocardial ischemia, infarction, and
inflammation. However, the mechanisms involved in the induction and regulation
of WISP1 under these conditions have not been well characterized.The proinflammatory cytokine tumor necrosis factor (TNF)-α is
expressed at low basal levels in the normal myocardium but is significantly
up-regulated after infection, inflammation, and injury
(14,
15). Although low levels are
considered cytoprotective (16,
17), aberrant expression of
TNF-α during myocardial ischemic injury and inflammation induces
cardiomyocyte death, hypertrophy of surviving cardiomyocytes, contractile
dysfunction, fibroblast proliferation, fibrosis, and adverse remodeling
(14–17).
TNF-α exerts its biological effects via two cell surface receptors,
TNFR1 (55 kDa) and TNFR2 (75 kDa)
(18). TNFR1, which is more
abundantly expressed in the heart, appears to be the main signaling receptor
for TNF-α and is implicated in transmitting its deleterious effects
(18). On the other hand,
signaling through TNFR2 appears to exert a protective effect in the heart
(18,
19). Of note, all myocardial
constituent cells, including fibroblasts, express both TNFR1 and TNFR2 and,
therefore, are targets of TNF-α.We have recently demonstrated that TNF-α induces WISP1 expression in
cardiomyocytes (13). However,
neither its localization in post-infarct myocardium, its role in
TNF-α-mediated cardiac fibroblast (CF) proliferation and collagen
production, nor its effects on TNF-α-mediated cardiomyocyte death are
known. Our results show that both TNF-α and WISP1 are localized in the
border zone and the non-infarct remote region in post-infarct myocardium.
Furthermore, TNF-α induces WISP1 expression in CF via a
TNFR2/MEK1/ERK1/2/CREB pathway and stimulates fibroblast collagen production
in part via WISP1. In addition, WISP1 exerts pro-survival effects in
cardiomyocytes, antagonizing TNF-α-mediated cardiomyocyte death.
Collectively, these results indicate that WISP1 exerts pro-mitogenic and
pro-survival effects in cardiac cell type-specific manner, and
TNF-α/WISP1 signaling may be an important contributing mechanism in
post-infarct cardiac remodeling. 相似文献
14.
Cell death can be divided into the anti-inflammatory process of apoptosis and the
pro-inflammatory process of necrosis. Necrosis, as apoptosis, is a regulated form of cell
death, and Poly-(ADP-Ribose) Polymerase-1 (PARP-1) and Receptor-Interacting Protein (RIP)
1/3 are major mediators. We previously showed that absence or inhibition of PARP-1
protects mice from nephritis, however only the male mice. We therefore hypothesized that
there is an inherent difference in the cell death program between the sexes. We show here
that in an immune-mediated nephritis model, female mice show increased apoptosis compared
to male mice. Treatment of the male mice with estrogens induced apoptosis to levels
similar to that in female mice and inhibited necrosis. Although PARP-1 was activated in
both male and female mice, PARP-1 inhibition reduced necrosis only in the male mice. We
also show that deletion of RIP-3 did not have a sex bias. We demonstrate here that male
and female mice are prone to different types of cell death. Our data also suggest that
estrogens and PARP-1 are two of the mediators of the sex-bias in cell death. We therefore
propose that targeting cell death based on sex will lead to tailored and better treatments
for each gender. 相似文献
15.
Sinularia leptoclados (Ehrenberg, 1834) is re-described. Sinularia leptoclados var. gonatodes Kolonko, 1926 is synonymized with Sinularia maxima Verseveldt, 1977. Two new species of Sinularia with digitiform lobules, leptoclados-type surface clubs and unbranched interior spindles, are described. An updated maximum likelihood tree of Sinularia species with leptoclados-type clubs (clade 5C) based on two mitochondrial genes (mtMutS, COI) and a nuclear gene (28S rDNA) is presented. 相似文献
16.
A new genus of Isotomidae, Bellisotoma
gen. n., is described. The new genus is a member of the Proisotoma genus complex and is characterized by a combination of having a bidentate mucro with wide dorsal lamellae that join clearly before the end of mucronal axis without forming a tooth and one strong ventral rib with basal notch that articulates with dens; having abundant chaetotaxy on both faces of dens; and abundant tergal sensilla. Bellisotoma gen. n. shows a furcula adapted to a neustonic mode of life, and may be a Isotopenola-like derivative adapted to neustonic habitats. Subisotoma joycei Soto-Adames & Giordano, 2011 and Ballistura ewingi James, 1933 are transferred to the new genus. 相似文献
17.
Six species of Gastrocopta have been identified from the Pilbara region, Western Australia, by means of comparative analyses of shell and mtDNA variation. Three of these species, Gastrocopta hedleyi, Gastrocopta larapinta and Gastrocopta servilis, have been recorded in the Pilbara for the first time. Gastrocopta sp. CW1 is probably new to science and might be endemic to the region. By contrast, Gastrocopta hedleyi, Gastrocopta larapinta and Gastrocopta mussoni are shown to be widespread. 相似文献
18.
Wilfredo A. Matamoros Jacob F. Schaefer Carmen L. Hernández Prosanta?Chakrabarty 《ZooKeys》2012,(227):49-62
A new species of Profundulus, Profundulus kreiseri (Cyprinodontiformes: Profundulidae), is described from the Chamelecón and Ulúa Rivers in the northwestern Honduran highlands. Based on a phylogenetic analysis using cytochrome b and the presence of synapomorphic characters (dark humeral spot, a scaled preorbital region and between 32-34 vertebrae), this new species is placed in the subgenus Profundulus, which also includes Profundulus (Profundulus) oaxacae, Profundulus (Profundulus) punctatus and Profundulus (Profundulus) guatemalensis. Profundulus kreiseri can be distinguished from other members of the subgenus Profundulus by having less than half of its caudal fin densely scaled. Profundulus kreiseri can further be differentiated from Profundulus (Profundulus) oaxacae and Profundulus (Profundulus) punctatus by the absence of rows of dark spots on its flanks. The new species can further be differentiated from Profundulus (Profundulus) guatemalensis by the presence of fewer caudal- and pectoral-fin rays. The new species is distinguished from congeners of the profundulid subgenus Tlaloc (viz., Profundulus (Tlaloc) hildebrandi, Profundulus (Tlaloc) labialis, Profundulus (Tlaloc) candalarius and Profundulus (Tlaloc) portillorum) by having a scaled preorbital region and a dark humeral spot. Profundulus kreiseri and Profundulus portillorum are the only two species of Profundulus that are endemic to the region south of the Motagua River drainage in southern Guatemala and northwestern Honduras. 相似文献
19.
Two new species Dacne (Xenodacne) tangliangi
sp. n. andDacne (Xenodacne) hujiayaoi
sp. n. are described from China. A key to Chinese species and subspecies of genus Dacne Latreille is provided. 相似文献