共查询到20条相似文献,搜索用时 15 毫秒
1.
O'Sullivan JA Zloza A Kohlhapp FJ Moore TV Lacek AT Dulin NO Guevara-Patiño JA 《Cancer immunology, immunotherapy : CII》2011,60(11):1543-1551
While the effects of TCR affinity and TGFβ on CD8+ T-cell function have been studied individually, the manner in which TCR affinity dictates susceptibility to TGFβ-mediated
suppression remains unknown. To address this issue, we utilized OVA altered peptide ligands (APLs) of different affinities
in the OT-I model. We demonstrate that while decreased TCR ligand affinity initially results in weakened responses, such interactions
prime the resultant effector cells to respond more strongly to cognate antigen upon secondary exposure. Despite this, responses
by CD8+ T cells primed with lower-affinity TCR ligands are more effectively regulated by TGFβ. Susceptibility to TGFβ-mediated suppression
is associated with downregulation of RGS3, a recently recognized negative regulator of TGFβ signaling, but not expression
of TGFβ receptors I/II. These results suggest a novel tolerance mechanism whereby CD8+ T cells are discriminately regulated by TGFβ according to the affinity of the ligand on which they were initially primed.
In addition, because of the major role played by TGFβ in tumor-induced immune suppression, these results identify the affinity
of the priming ligand as a primary concern in CD8+ T-cell-mediated cancer immunotherapeutic strategies. 相似文献
2.
Alan M. Holmes Markella Ponticos Xu Shi-wen Christopher P. Denton David J. Abraham 《Journal of cell communication and signaling》2011,5(3):173-177
The ability of TGFβ1 to act as a potent pro-fibrotic mediator is well established, potently inducing the expression of fibrogenic
genes including type I collagen (COL1A2) and CCN2. Previously we have shown elevated expression of the TGFβ accessory receptor,
endoglin on Systemic Sclerosis (SSc) dermal fibroblasts. Here we sought to assess the cell surface expression of the TGFβ
receptor complex on SSc dermal fibroblasts (SDF), and investigate their role in maintaining the elevated expression of CCN2.
SDF exhibited elevated expression of the TGFβ accessory receptors betaglycan/TGFβRIII and endoglin, but not type I or type
II receptors. To determine the effect of altered receptor repertoire on TGFβ responses, we investigated the effect of exogenous
TGFβ on expression of two pro-fibrotic genes. SDF exhibited higher basal expression of COL1A2 and CCN2 compared to healthy
controls. TGFβ induced a marked increase in the expression of these genes in normal dermal fibroblasts, whereas SDF exhibited
only a modest increase. We next sought to determine if higher basal expression in SDF was a result of autocrine expression
of TGFβ. Surprisingly basal expression was not affected by a pan-neutralizing TGFβ antibody. To explore if altered accessory
receptor expression alone could account for these changes, we determined their effects on CCN2 promoter activity. Endoglin
inhibited CCN2 promoter activity in response to TGFβ. TGFβRIII alone or in combination with endoglin was sufficient to enhance
basal CCN2 promoter activity. Thus TGFβ accessory receptors may play a significant role in the altered expression of fibrogenic
genes in SDF. 相似文献
3.
Yuhu Song Fang Liu Dean Tian Xiulan Xue Nanzhi Liu Xiaoli Wu Jusheng Lin Youxin Jin 《中国科学:生命科学英文版》2006,49(1):73-81
Transforming growth factorβ1 (TGFβ1) is known to be intimately involved in many cellular processes. To explore the mechanism of TGFβ1 in these processes, the non-chimeric hammerhead ribozyme and U1 snRNA chimeric ribozyme against TGFβ1 were designed to down-regulate TGFβ1 expression. The activity of non-chimeric ribozyme and U1 snRNA chimeric ribozyme against TGFβ1 in vitro and in activated hepatic stellate cells (HSCs) was detected. Cleavage reactions of both ribozymes in vitro demonstrated that non-chimeric ribozyme possessed better cleavage activity in vitro than U1 snRNA chimeric ribozyme. The further study showed U1 snRNA chimeric ribozyme inhibited TGFβ1 expression more efficiently than non-chimeric ribozyme in transfected HSC cells. So it indicates that the U1 snRNA chimeric ribozyme provides an alternative approach for the research on the precise mechanism of TGFβ1 in many cellular processes and a potential therapeutic candidate for TGFβ1-related diseases. 相似文献
4.
SONG Yuhu LIU Fang TIAN Dean XUE Xiulan LIU Nanzhi WU Xiaoli LIN Jusheng JIN Youxin 《中国科学C辑(英文版)》2006,49(1):73-81
Transforming growth factorβ1 (TGFβ1) is known to be intimately involved in many cellular processes. To explore the mechanism
of TGFβ1 in these processes, the non-chimeric hammer-head ribozyme and U1 snRNA chimeric ribozyme against TGFβ1 were designed
to down-regulate TGFβ1 expression. The activity of non-chimeric ribozyme and U1 snRNA chimeric ribozyme against TGFβ1 in vitro and in activated hepatic stellate cells (HSCs) was detected. Cleavage reactions of both ribozymes in vitro demonstrated that non-chimeric ribozyme possessed better cleavage activity in vitro than U1 snRNA chimeric ribozyme. The further study showed U1 snRNA chimeric ribozyme inhibited TGFβ1 expression more efficiently
than non-chimeric ribozyme in transfected HSC cells. So it indicates that the U1 snRNA chimeric ribozyme provides an alternative
approach for the research on the precise mechanism of TGFβ1 in many cellular processes and a potential therapeutic candidate
for TGFβ1-related diseases. 相似文献
5.
Gardner CR 《Cell and tissue research》2007,330(1):111-121
RANKL, in the presence of M-CSF, induces the development and fusion of TRAP+ osteoclasts in mouse bone marrow cultures at
3–5 days. Early during culture (day 3), most cells are small (up to six nuclei). At lower cell densities, these osteoclasts
exhibit a rounded morphology with cytoplasm extending around the cells but, at higher densities, this changes to a stellate
morphology with the cytoplasm being retracted around the nuclei with numerous localised cytoplasmic extensions. Under optimal
conditions, osteoclast fusion results in conglomerates of many cells, which become large cytoplasmic masses on day 4. PGE2
and TGFβ have both been shown to increase osteoclast development in this model and their effects on the morphology of osteoclasts
during fusion and differentiation have been compared under all these conditions. PGE2 or TGFβ increase osteoclast numbers
and size and also the number of nuclei, indicating increased osteoclast development and fusion. TGFβ increases the size of
rounded osteoclasts (with respect to the number of nuclei) more than PGE2, suggesting that TGFβ increases cytoplasmic extension.
TGFβ increases the size and number of nuclei in stellate cells but particularly increases the number and length of the cytoplasmic
extensions, in contrast to PGE2. Fusion of these extensions with other osteoclasts results in large networks of interconnected
cells. On day 4, spreading cells develop but these are still interconnected by cytoplasmic links, a phenomenon not seen in
control wells or after treatment with PGE2. TGFβ is more effective than PGE2 in increasing fusion in the formation of cell
conglomerates and cytoplasmic masses. PGE2 decreases overall cell density resulting in additional indirect effects on osteoclast
numbers and morphology. However, PGE2 particularly promotes the formation of large mature spreading osteoclasts later during
culture. 相似文献
6.
Akiyoshi Taniguchi Koichi Matsuzaki Katsuya Nakano Mikio Kan Wallace L. Mckeehan 《In vitro cellular & developmental biology. Animal》1998,34(3):232-238
Summary The type III receptor for transforming growth factor beta (TGFβ), which exhibits no kinase activity, binds TGFβ1 and TGFβ2
and is involved in assembly and activity of the multi-subunit TGFβ signal transduction complex. Recently we showed that TGFβ
receptor type III (TβRIII) can participate in a complex composed of the dimeric TGFβ ligand and a type III, II, and I receptor
subunit. The interaction of the TβRIII subunit with TβRII is TGFβ-dependent, whereas interaction with TβRI is TGFβ-independent.
Here we use coexpression of the three types of TGFβ receptors in baculoviral-infected insect cells to determine which parts
of the unglycosylated TβRIII receptor participate in the binding of TGFβ, the TGFβ-dependent interaction with TβRII and the
TGFβ-independent interaction with TβRI. The results suggest that the first 500 amino acid residues in the aminoterminal portion
of TβRIII exhibit all three properties. 相似文献
7.
Peter M van der Kraan Esmeralda N Blaney Davidson Wim B van den Berg 《Arthritis research & therapy》2010,12(1):201
Transforming growth factor beta (TGFβ) is a growth factor with many faces. In our osteoarthritis (OA) research we have found
that TGFβ can be protective as well as deleterious for articular cartilage. We postulate that the dual effects of TGFβ on
chondrocytes can be explained by the fact that TGFβ can signal via different receptors and related Smad signaling routes.
On chondrocytes, TGFβ not only signals via the canonical type I receptor ALK5 but also via the ALK1 receptor. Notably, signaling
via ALK5 (Smad2/3 route) results in markedly different chondrocyte responses than ALK1 signaling (Smad1/5/8), and we postulate
that the balance between ALK5 and ALK1 expression on chondrocytes will determine the overall effect of TGFβ on these cells.
Importantly, signaling via ALK1, but not ALK5, stimulates MMP-13 expression by chondrocytes. In cartilage of ageing mice and
in experimental OA models we have found that the ALK1/ALK5 ratio is significantly increased, favoring TGFβ signaling via the
Smad1/5/8 route, changes in chondrocyte differentiation and MMP-13 expression. Moreover, human OA cartilage showed a significant
correlation between ALK1 and MMP-13 expression. In this paper we summarize concepts in OA, its link with ageing and disturbed
growth factor responses, and a potential role of TGFβ signaling in OA development. 相似文献
8.
Phenotype transformation of corneal keratocyte to myofibroblast plays an important role in the wound healing process of cornea
and TGFβ is considered to be the most important mediator to induce myofibroblast trans-differentiation. Peroxisome proliferator-activated
receptors-γ (PPAR-γ) activation has been proved to exert anti-fibrotic effect in many tissues. In this study, we investigated
the effect of PPAR-γ agonist, pioglitazone, on myofibroblast transformation, extracellular matrix production and cell proliferation.
The results showed pioglitazone inhibited the TGFβ-driven myofibroblast differentiation, as determined by F-actin fluorescence
staining, α-smooth muscle actin-specific immunocytochemistry and western blot analysis. Pioglitazone also potently attenuated
TGFβ induced type I collagen and fibronectin mRNA and protein production. Moreover, pioglitazone showed inhibitory effect
on TGFβ induced cell proliferation. The irreversible PPAR-γ antagonist GW9662, partially reversed the inhibition of collagen
I and fibronectin expression but not myofibroblast transformation, suggesting both PPAR-γ dependent and PPAR-γ independent
mechanisms were involved in the action of pioglitazone. Therefore, our study indicates pioglitazone has a potential application
in therapy of corneal fibrosis and PPAR-γ might be a promising therapy target. 相似文献
9.
Robert Olaso Catherine Pairault José-Maria Saez R. Habert 《Histochemistry and cell biology》1999,112(3):247-254
The localization of transforming growth factor β3 (TGFβ3) in the fetal and neonatal testis (from fetal day 13.5 to postnatal
day 6) was investigated by immunohistochemical staining with a specific polyclonal antibody raised against a synthetic peptide
corresponding to residues 50–75 of TGFβ3. This antibody recognized 0.5 ng TGFβ3 in western blot analysis, but did not detect
25 ng TGFβ1 or TGFβ2. The immunolocalization of TGFβ3 in the fetal and neonatal testis changed throughout development. Immunostaining
was present in the gonocytes by fetal day 13.5, persisted until postnatal day 3, and was heterogeneous in spermatogonia on
postnatal day 6. The Sertoli cells contained no immunoreactivity at any age. The fetal-type Leydig cells were first immunostained
for TGFβ3 on day 16.5 and staining became very intense from day 18.5 onward. Staining disappeared when the antibody was presaturated
with the synthetic peptide, but persisted when the antibody was presaturated with a tenfold excess of the corresponding peptide
from TGFβ2. Furthermore, we researched whether TGFβ3 could act as a local regulator of fetal Leydig cell function. In a dispersed
fetal testicular cell system, TGFβ3 inhibited the LH-stimulated testosterone production by Leydig cells from 20.5-day-old
fetuses. The inhibitory effect of TGFβ3 was equal to that observed with TGFβ1 or TGFβ2. When compared with our previous studies
showing the immunolocalization of TGFβ1 and TGFβ2, the present study shows that TGFβ3 may have a specific role in the developing
rat testis, but may also overlap the action of TGFβ1 and TGFβ2.
Accepted: 8 June 1999 相似文献
10.
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12.
Hasem Habelhah Futoshi Okada Kazumoto Nakai Sung Ki Choi Jun-ichi Hamada Masanobu Kobayashi M. Hosokawa 《Cancer immunology, immunotherapy : CII》1998,46(6):338-344
Previously we reported the malignant progression of QR-32, a regressor-type tumor clone, following co-implantation with foreign
bodies (gelatin sponge or plastic plate) in normal syngeneic C57BL/6 mice. We also reported that the progression of QR-32
cells by a gelatin sponge was significantly inhibited in the mice administered polysaccharide K (PSK) and that PSK induced
an increase of radical scavengers, especially manganese superoxide dismutase (Mn-SOD), locally at the site of tumor tissues.
In this study, to reveal the possible mechanism by which PSK induced Mn-SOD in the tumor tissues, we examined the mRNA expression
and protein levels of inflammatory cytokines in the tissues. We found that mRNAs of tumor necrosis factor α (TNFα) and interleukin-1α
(IL-1α) were considerably expressed in both PSK-treated and phosphate-buffered-saline-treated tumors, and that the mRNA expression
and protein level of interferon γ (IFNγ) increased in the tumor tissues treated with PSK. In vitro treatment of QR-32 cells
with IFNγ did not significantly increase the production of Mn-SOD; however, the combination of IFNγ with TNFα increased the
Mn-SOD production more effectively than did any of the cytokines used singly. Furthermore, we observed the down-regulation
of the mRNA expression and protein level of transforming growth factor β (TGFβ) in the tumor tissues treated with PSK, and
that in vitro treatment of QR-32 cells with TGFβ decreased the production of Mn-SOD. These results suggest that PSK suppresses
the progression of QR-32 cells by increasing Mn-SOD via the modulation of inflammatory cytokines; that is, by decreasing TGF-β
and increasing IFN-γ.
Received: 7 October 1997 / Accepted: 31 March 1998 相似文献
13.
Esmeralda N Blaney Davidson Elly L Vitters Wim B van den Berg Peter M van der Kraan 《Arthritis research & therapy》2006,8(3):R65-8
Cartilage damage in osteoarthritis (OA) is considered an imbalance between catabolic and anabolic factors, favoring the catabolic
side. We assessed whether adenoviral overexpression of transforming growth factor-β (TGFβ) enhanced cartilage repair and whether
TGFβ-induced fibrosis was blocked by local expression of the intracellular TGFβ inhibitor Smad7. We inflicted cartilage damage
by injection of interleukin-1 (IL-1) into murine knee joints. After 2 days, we injected an adenovirus encoding TGFβ. On day
4, we measured proteoglycan (PG) synthesis and content. To examine whether we could block TGFβ-induced fibrosis and stimulate
cartilage repair simultaneously, we injected Ad-TGFβ and Ad-Smad7. This was performed both after IL-1-induced damage and in
a model of primary OA. In addition to PG in cartilage, synovial fibrosis was measured by determining the synovial width and
the number of procollagen I-expressing cells. Adenoviral overexpression of TGFβ restored the IL-1-induced reduction in PG
content and increased PG synthesis. TGFβ-induced an elevation in PG content in cartilage of the OA model. TGFβ-induced synovial
fibrosis was strongly diminished by simultaneous synovial overexpression of Smad7 in the synovial lining. Of great interest,
overexpression of Smad7 did not reduce the repair-stimulating effect of TGFβ on cartilage. Adenoviral overexpression of TGFβ
stimulated repair of IL-1- and OA-damaged cartilage. TGFβ-induced synovial fibrosis was blocked by locally inhibiting TGFβ
signaling in the synovial lining by simultaneously transfecting it with an adenovirus overexpressing Smad7. 相似文献
14.
Ming Ding James J. Potter Xiaopu Liu Michael S. Torbenson Esteban Mezey 《Biological trace element research》2010,133(1):83-97
Oxidative stress stimulates fibrogenesis, and selenium (Se) has antioxidant properties. This study determined whether Se supplementation
affects CCl4-induced liver injury and fibrosis. Mice were administered CCl4 over 4 weeks, while controls received olive oil. Se was provided as sodium selenite in the drinking water. Se increased liver
Se-dependent glutathione peroxidase activity and decreased liver malondialdehyde after CCl4. Se decreased liver inflammation but not necrosis caused by CCl4. Se increased hepatocyte apoptosis after CCl4 and the pro-apoptotic BAX and Bcl Xs/l proteins. Stellate cell apoptosis occurred only after CCl4 in Se-supplemented mice. Se decreased stellate cell number and fibrosis after CCl4. Liver matrix metalloproteinase-9 increased after CCl4 with Se supplementation. In conclusion, Se supplementation decreased hepatic fibrosis after CCl4 in the setting of decreased inflammation but increased apoptosis. The principal mechanisms for the decreased fibrosis are
a lower number of collagen-producing stellate cells and increased collagen degradation. 相似文献
15.
Cytochrome P450 2E1-derived reactive oxygen species mediate paracrine stimulation of collagen I protein synthesis by hepatic stellate cells. 总被引:3,自引:0,他引:3
Natalia Nieto Scott L Friedman Arthur I Cederbaum 《The Journal of biological chemistry》2002,277(12):9853-9864
To evaluate possible fibrogenic effects of CYP2E1-dependent generation of reactive oxygen species, a model was developed using co-cultures of HepG2 cells, which do (E47 cells) or do not (C34 cells) express cytochrome P450 2E1 (CYP2E1) with stellate cells. There was an increase in intra- and extracellular H(2)O(2), lipid peroxidation, and collagen type I protein in stellate cells co-cultured with E47 cells compared with stellate cells alone or co-cultured with C34 cells. The increase in collagen was prevented by antioxidants and a CYP2E1 inhibitor. CYP3A4 did not mimic the stimulatory effects found with CYP2E1. Collagen mRNA levels remained unchanged, and pulse-chase analysis indicated similar half-lives of collagen I protein between both co-cultures. However, collagen protein synthesis was increased in E47 co-culture. Hepatocytes from pyrazole-treated rats (with high levels of CYP2E1) induced collagen protein in primary stellate cells, and antioxidants and CYP2E1 inhibitors blocked this effect. These results suggest that increased translation of collagen mRNA by CYP2E1-derived reactive oxygen species is responsible for the increase in collagen protein produced by the E47 co-culture. These co-culture models may be useful for understanding the impact of CYP2E1-derived ROS on stellate cell function and activation. 相似文献
16.
A bacterium (strain HC1) capable of assimilating rice bran hemicellulose was isolated from a soil and identified as belonging
to the genus Paenibacillus through taxonomical and 16S rDNA sequence analysis. Strain HC1 cells grown on rice bran hemicellulose as a sole carbon source
inducibly produced extracellular xylanase and intracellular glycosidases such as β-d-glucosidase and β-d-arabinosidase. One of them, β-d-glucosidase was further analyzed. A genomic DNA library of the bacterium was constructed in Escherichia coli and gene coding for β-d-glucosidase was cloned by screening for β-d-glucoside-degrading phenotype in E. coli cells. Nucleotide sequence determination indicated that the gene for the enzyme contained an open reading frame consisting
of 1,347 bp coding for a polypeptide with a molecular mass of 51.4 kDa. The polypeptide exhibits significant homology with
other bacterial β-d-glucosidases and belongs to glycoside hydrolase family 1. β-d-Glucosidase purified from E. coli cells was a monomeric enzyme with a molecular mass of 50 kDa most active at around pH 7.0 and 37°C. Strain HC1 glycosidases
responsible for degradation of rice bran hemicellulose are expected to be useful for structurally determining and molecularly
modifying rice bran hemicellulose and its derivatives. 相似文献
17.
After having established the specificity of the antibodies for the rat testis by western blot analysis, the potential target
cells for transforming growth factors (TGFβs) were identified by immunohistochemical detection of both type I (TβRI) and type
II (TβRII) transducing receptors for TGFβs in the adult rat testis in situ. Leydig cells showed a strong TβRII immunoreactivity
whereas the TβRI staining was weak. Only TβRII was detectable in Sertoli cells. In germ cells, staining for TβRI was stronger
than for TβRII and the expression of both receptors depended on the seminiferous cycle stage. TβRI first appeared in pachytene
spermatocytes and was absent in elongated spermatids from stage XIV onwards. Labelling for TβRII was observed as early as
the spermatogonia stage; it increased in pachytene spermatocytes at the onset of TβRI and disappeared in elongating spermatids
from stage XI onwards. These results show that TGFβs can affect somatic cells functions and suggest that these factors are
involved in the control of meiosis and early spermiogenesis, exerting a direct effect on germ cells.
Accepted: 18 June 1998 相似文献
18.
Matsuzaki K 《Cell and tissue research》2012,347(1):225-243
Hepatocellular carcinoma (HCC) usually arises from hepatic fibrosis caused by chronic inflammation. In chronic liver damage,
hepatic stellate cells undergo progressive activation to myofibroblasts (MFB), which are important extracellular-matrix-producing
mesenchymal cells. Concomitantly, perturbation of transforming growth factor (TGF)-β signaling by pro-inflammatory cytokines
in the epithelial cells of the liver (hepatocytes) promotes both fibrogenesis and carcinogenesis (fibro-carcinogenesis). Insights
into fibro-carcinogenic effects on chronically damaged hepatocytes have come from recent detailed analyses of the TGF-β signaling
process. Smad proteins, which convey signals from TGF-β receptors to the nucleus, have intermediate linker regions between
conserved Mad homology (MH) 1 and MH2 domains. TGF-β type I receptor and pro-inflammatory cytokine-activated kinases differentially
phosphorylate Smad2 and Smad3 to create phosphoisoforms phosphorylated at the COOH-terminal, linker, or both (L/C) regions.
After acute liver injury, TGF-β-mediated pSmad3C signaling terminates hepatocytic proliferation induced by the pro-inflammatory
cytokine-mediated mitogenic pSmad3L pathway; TGF-β and pro-inflammatory cytokines synergistically enhance collagen synthesis
by activated hepatic stellate cells via pSmad2L/C and pSmad3L/C pathways. During chronic liver disease progression, pre-neoplastic
hepatocytes persistently affected by TGF-β together with pro-inflammatory cytokines come to exhibit the same carcinogenic
(mitogenic) pSmad3L and fibrogenic pSmad2L/C signaling as do MFB, thereby accelerating liver fibrosis while increasing risk
of HCC. This review of Smad phosphoisoform-mediated signals examines similarities and differences between epithelial and mesenchymal
cells in acute and chronic liver injuries and considers Smad linker phosphorylation as a potential target for the chemoprevention
of fibro-carcinogenesis. 相似文献
19.
Koichi Matsuzaki Mikio Kan Wallace L. McKeehan 《In vitro cellular & developmental biology. Animal》1996,32(6):345-360
Summary Two transmembrane serine-threonine kinases (type I and II receptors), a membrane-anchored proteoglycan (type III), and a homodimeric
ligand participate in the transforming growth factor beta type on (TGFβ1) signal transduction complex. The expression of recombinant
receptors in insect cells co-infected with up to three recombinant baculoviruses was employed to study interactions among
the ectodomains of the three types of receptors and the TGFβ1 ligand in absence of uncontrollable extrinsic factors in mammalian
cells. Multi-subunit complexes were assembled in intact cells and purified on glutathione-conjugated beads for analysis by
tagging one of the subunits with glutathione S-transferase (GST). Intrinsic ligand-independent interactions were observed
among receptor subunits as follows: type III–III type I–I, type III-I, and type II-I. The homeotypic complex of type II–II
receptors and the heterotypic type III-II interaction was ligand dependent. The type I, but not the type III, subunit displaced
about 50% of the type II component in either ligand-dependent homomeric type II-type II complexes or heteromeric type III-type
II complexes to form type II-I or type III-II-I oligomers, respectively. The type II subunit displaced type I subunits in
oligomers of the type I subunit. Specificity of type I receptors may result from differential affinity for the type II receptor
rather than specificity for ligand. A monomeric subunit of the TGFβ1 ligand bound concurrently to type III and type II or
type III and type I receptors, but failed to concurrently bind to the type II and type I subunits. The binding of TGFβ1 to
the type I kinase subunit appears to require an intact disulfide-linked ligand dimer in the absence of a type III subunit.
The combined results suggest a pentameric TGFβ signal transduction complex in which one unit each of the type III, type II,
and type I components is assembled around the two subunits of the dimeric TGFβ1 ligand. An immobilized GST-tagged subunit
of the receptor complex was utilized to assemble multi-subunit complexesin vitro and to study the phosphorylation events among subunits in the absence of extrinsic cell-derived kinases. The results revealed
that (a) a low level of ligand-independent autophosphorylation occurs in the type I kinase; (b) a high level of autophosphorylation
occurs in the type II kinase; (c) both the type III and type I subunits aretrans-phosphorylated by the type II subunit; and (d) the presence of both type I and II kinases complexed with the type III subunit
and dimeric TGFβ1 ligand in a pentameric complex causes maximum phosphorylation of all three receptor subunits. 相似文献
20.
We present the results obtained with an in vitro model system that resembles the in vivo tumour microenvironment, where malignant
cells are in close contact with the infiltrating lymphocytes. Unmanipulated blood lymphocytes were cytotoxic against the autologous
ex vivo tumour cells in 3/19 patients and this function was generated in 6-day mixed cultures in five additional cases. Production
of transforming growth factor β (TGFβ) by the freshly separated tumour cells was determined in parallel. Cytotoxicity was
generated by a small number of tumour cells (2–5/100 lymphocytes), while a large number (10–20/100 lymphocytes) inhibited
not only the generation but also the existing lytic activity. The presence of a neutralising TGFβ-specific mAb (2G7) potentiated
the activation of lymphocytes and suspended the suppression inflicted by the tumour cells. In those tumours, which expressed
relatively high levels of MHC class I and ICAM-1 molecules, the quantity of secreted TGFβ interfered with the ability of tumour
cells to generate cytotoxic lymphocytes. In the tumours with low expression of class I, such a correlation was not detected,
indicating the primordial role of MHC class I expression in the regulation of autologous tumour recognition. Our results demonstrate
the involvement of TGFβ in the impaired lymphocyte-mediated reactivity against immunogenic tumours and support a mechanism
that contrasts the tolerance or anergy. Since presence of TGFβ in the microenvironment of tumours counteracts the function
of cytotoxic T lymphocytes, production of this cytokine can contribute to the failure of immunotherapy.
Received: 19 June 1997 / Accepted: 14 August 1997 相似文献