Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P05109 (S100A8)
 1,212 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Smad proteins play a key role in the intracellular signalling of transforming growth factor beta (TGF beta), which elicits a large variety of cellular responses. Upon TGF beta receptor activation, Smad2 and Smad3 become phosphorylated and form heteromeric complexes with Smad4. These complexes translocate to the nucleus where they control expression of target genes. However, the mechanism by which Smads mediate transcriptional regulation is largely unknown. Human plasminogen activator inhibitor-1 (PAI-1) is a gene that is potently induced by TGF beta. Here we report the identification of Smad3/Smad4 binding sequences, termed CAGA boxes, within the promoter of the human PAI-1 gene. The CAGA boxes confer TGF beta and activin, but not bone morphogenetic protein (BMP) stimulation to a heterologous promoter reporter construct. Importantly, mutation of the three CAGA boxes present in the PAI-1 promoter was found to abolish TGF beta responsiveness. Thus, CAGA elements are essential and sufficient for the induction by TGF beta. In addition, TGFbeta induces the binding of a Smad3/Smad4-containing nuclear complex to CAGA boxes. Furthermore, bacterially expressed Smad3 and Smad4 proteins, but not Smad1 nor Smad2 protein, bind directly to this sequence in vitro. The presence of this box in TGF beta-responsive regions of several other genes suggests that this may be a widely used motif in TGF beta-regulated transcription.
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PMID:Direct binding of Smad3 and Smad4 to critical TGF beta-inducible elements in the promoter of human plasminogen activator inhibitor-type 1 gene. 960 91

A panel of 6 human glioma cell lines was examined for TGF-beta1 responsiveness. U-178 MG and U-251 MG AgCl1 were significantly inhibited by TGF-beta1, while U-343 MGa 31L and U-343 MGa 35L were potently stimulated to proliferate. TGF-beta1 induced endogenous PAI-1 protein synthesis, Smad binding element/(CAGA)12-luciferase-reporter activity, as well as mRNA expression of Smad6 and Smad7 in all gliomas. Interestingly, TGF-beta1 differentially stimulated or inhibited the expression of TbetaR-I and TbetaR-II mRNA in the gliomas. Affinity cross-linking studies using 125I-TGF-beta1 revealed that the gliomas expressed TGF-beta-type-I(TbetaR-I) and -type-II(TbetaR-II) receptors, although binding to TbetaR-II in U-343 MGa 31L and U-251 MG AgCl1 was low to undetectable. Smad2 protein was abundantly present in U-178 MG, U-343 MG, and U-343 MGa 35L, while Smad3 was readily detectable in U-178 MG, U-343 MG, U-343 MGa 35L and U-251 MG AgCl1. In all gliomas, TGF-beta1 induced phosphorylation of Smad2. The level to which TGF-beta1 could activate the pathway leading to induction of the (CAGA)12-luciferase reporter seemed to correlate to the expression levels of TGF-beta receptors, Smad3 and Smad4 proteins. However, despite the plethora of data regarding TGF-beta1 signalling in the different glioma cell lines, the mechanism underlying the differential growth effects mediated by TGF-beta1 is still unclear. The results suggest that a complex balance between several components in the TGF-beta signalling pathway controls glioma responsiveness to TGF-beta1, and extend reports indicating that distinct signal transduction pathways are involved in growth inhibition and other cellular responses.
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PMID:Expression of transforming-growth-factor (TGF)-beta receptors and Smad proteins in glioblastoma cell lines with distinct responses to TGF-beta1. 1004 79

Proteins secreted by epidermal keratinocytes are known to engage in functions other than those directly associated with barrier formation. We have used a previously published culture model to collect proteins secreted by adult human epidermal keratinocytes. Electrophoresis and microsequencing allowed us to identify 20 proteins. The list of proteins includes those known to be produced by keratinocytes (beta-2 microglobulin, betaIG-H3, calgranulin A, cathepsin B and D, E-cadherin, gelatinase B, gelsolin, interstitial collagenase, laminin B2t, plasminogen activator inhibitor-1, protein 14-3-3epsilon, SCC antigen, stratifin, and translationally controlled tumor protein) as well as those not previously known to be secreted by keratinocytes (epididymis secretory protein, maspin, and anti-neoplastic urinary protein). In addition, two proteins were identified that are not known to be secreted (glutathione-S-transferase and heat shock protein 27/28 kDa). The varied nature of the proteins identified suggests that epidermal keratinocytes have physiologic functions that have yet to be identified.
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PMID:A partial catalog of proteins secreted by epidermal keratinocytes in culture. 1023 78

The tissue type plasminogen activator (t-PA) is a serine protease that is involved in neuronal plasticity and cell death induced by excitotoxins and ischemia in the brain. t-PA activity in the central nervous system is regulated through the activation of serine protease inhibitors (serpins) such as the plasminogen activator inhibitor (PAI-1), the protease nexin-1 (PN-1), and neuroserpin (NSP). Recently we demonstrated in vitro that PAI-1 produced by astrocytes mediates the neuroprotective effect of the transforming growth factor-beta1 (TGF-beta1) in NMDA-induced neuronal cell death. To investigate whether serpins may be involved in neuronal cell death after cerebral ischemia, we determined, by using semiquantitative RT-PCR and in situ hybridization, that focal cerebral ischemia in mice induced a dramatic overexpression of PAI-1 without any effect on PN-1, NSP, or t-PA. Then we showed that although the expression of PAI-1 is restricted to astrocytes, PN-1, NSP, and t-PA are expressed in both neurons and astrocytes. Moreover, by using semiquantitative RT-PCR and Western blotting, we observed that only the expression of PAI-1 was modulated by TGF-beta1 treatment via a TGF-beta-inducible element contained in the PAI-1 promoter (CAGA box). Finally, we compared the specificity of TGF-beta1 action with other members of the TGF-beta family by using luciferase reporter genes. These data show that TGF-beta and activin were able to induce the overexpression of PAI-1 in astrocytes, but that bone morphogenetic proteins, glial cell line-derived neutrophic factor, and neurturin did not. These results provide new insights into the regulation of the serpins/t-PA axis and the mechanism by which TGF-beta may be neuroprotective.
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PMID:Transforming growth factor-beta1 as a regulator of the serpins/t-PA axis in cerebral ischemia. 1042 56

Transcription of the alpha2(I) collagen gene (COL1A2) in fibroblasts is potently induced by transforming growth factor-beta (TGF-beta). Smad family proteins function as intracellular signal transducers for TGF-beta that convey information from the cell membrane to the nucleus. In the present study, we establish the functional requirement for endogenous Smad3 and Smad4 in TGF-beta-stimulated COL1A2 transcription in human skin fibroblasts in vitro. Furthermore, using transfections with a series of 5' deletions of the human COL1A2 promoter, we identify a proximal region between -353 and -148 bp, which is required for full stimulation of transcription by a constitutively active TGF-beta type I receptor. This region of the COL1A2 promoter contains a CAGA motif also found in the promoter of the plasminogen activator inhibitor-1. Substitutions disrupting this sequence decreased the binding of nuclear extracts or recombinant Smad3 to the CAGACA oligonucleotide, and markedly reduced the transcriptional response to TGF-beta or overexpressed Smad3 in transient transfection assays. The insertion of tandem repeats of CAGACA conferred TGF-beta stimulation to a heterologous minimal promoter-reporter construct. Inhibition of endogenous Smad expression in fibroblasts by antisense oligonucleotides or cDNA against Smad3 or Smad4, and transfection of COL1A2 promoter constructs into Smad4-deficient breast adenocarcinoma cells, indicated the critical role of Smads for the full TGF-beta response. The importance of Smad binding to the CAGACA box of COL1A2 was further established by transcriptional decoy oligonucleotide competition. Taken together, the results identify a functional Smad-binding element of the COL1A2 promoter harboring a CAGACA consensus sequence that is both necessary and sufficient for stimulation by TGF-beta, and demonstrate that interaction of this Smad-binding element with endogenous Smads is required for the full TGF-beta response in fibroblasts.
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PMID:Interaction of smad3 with a proximal smad-binding element of the human alpha2(I) procollagen gene promoter required for transcriptional activation by TGF-beta. 1079 13

Bone morphogenetic protein-7 (BMP7) is expressed in adult kidney and reduces renal fibrogenesis when given exogenously to rodents with experimental chronic nephropathies. In mesangial cells that regulate glomerular fibrosis in vivo, BMP7 inhibits transforming growth factor beta (TGF-beta)-driven fibrogenesis, primarily by preventing the TGF-beta-dependent down-regulation of matrix degradation and up-regulation of PAI-1. The signals and mechanisms of the BMP7 opposition to actions of TGF-beta are unknown. Here we show in mesangial cells that BMP7 reduces nuclear accumulation of Smad3 and blocks the transcriptional up-regulation of the TGF-beta/Smad3 target, CAGA-lux. Smad5 knock-down impairs the ability of BMP7 to interfere with the activation of CAGA-lux and the accumulation of PAI-1 by TGF-beta indicating that Smad5 is required. Smad5 knock-down also reduces the rise in Smad6 upon BMP7. Forced expression of smad5 (found to be the preferred BMP7-induced receptor-activated Smad signal in mesangial cells) or of smad6 mimics BMP7 in opposing the increase in transcriptional activation of PAI-1 and its secretion upon TGF-beta. This suggests a model for the BMP7-induced opposition to TGF-beta-dependent mesangial fibrogenesis requiring Smad5; the model involves the inhibitory Smad6 downstream of Smad5 as well as reduced availability of Smad3 in the nucleus. BMP7 does not require signaling through Erk1/2, p38, or JNK and does not utilize the TGF-beta transcriptional co-repressors Ski or SnoN in mesangial cells. These studies provide first insights into mechanisms through which BMP7 opposes TGF-beta-induced glomerular fibrogenesis.
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PMID:Bone morphogenetic protein-7 signals opposing transforming growth factor beta in mesangial cells. 1504 7

Amadori-modified glycated albumin stimulates extracellular matrix and transforming growth factor-beta (TGF-beta) expression in cultured mesangial cells. Smad proteins transduce the TGF-beta-mediated signal, and Smad-binding CAGA sequences are present in the plasminogen activator inhibitor-1 (PAI-1) promoter. This study examined whether glycated albumin induces PAI-1 transcription in human mesangial cells (HMC) through Smad-binding sites in the PAI-1 promoter. Quiescent HMC were exposed to 200 microg/ml bovine serum albumin (BSA) or glycated BSA (Gly-BSA) for 12-72 h. At 24 h, Gly-BSA stimulated TGF-beta1 and PAI-1 mRNA expression in HMC to 1.8 and 3.2 times that in the BSA-treated control cells. Gly-BSA also activated the PAI-1 promoter luciferase activity 2.3-fold. Gly-BSA-treated cells enhanced Smad2 and Smad3 protein levels 2.5 times the control levels in the nuclei. An electrophoretic mobility shift assay performed using CAGA sequences as a probe showed that Gly-BSA increased DNA/protein complexes. When nuclear extracts were preincubated with 100-fold molar excess of unlabeled CAGA oligonucleotide, the formation of complex was prevented. The DNA-binding protein was shown to be Smad3 by antibody supershift. Transfection of phosphorothioate CAGA oligonucleotide, a CAGA antisense analog, inhibited Gly-BSA-induced PAI-1 mRNA expression. Cotransfection of phosphorothioate CAGA oligonucleotides with PAI-1 reporter vector also blocked Gly-BSA-induced PAI-1 promoter luciferase activity. These results indicate that Gly-BSA increases DNA binding activity of Smad3 and that it stimulates PAI-1 transcription through Smad-binding CAGA sequences in the PAI-1 promoter in HMC. Thus progression of diabetic nephropathy may be promoted by PAI-1 upregulation mediated by the glycated albumin-induced Smad/DNA interactions.
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PMID:Glycated albumin activates PAI-1 transcription through Smad DNA binding sites in mesangial cells. 1519 28

CD105 (endoglin) is an important component of the transforming growth factor-beta (TGF-beta) receptor complex and is highly expressed in endothelial cells in tissues undergoing angiogenesis such as healing wounds, infarcts and in a wide range of tumours. In an attempt to understand the molecular mechanism by which CD105 exerts its effects on angiogenesis by modulating TGF-beta1 signalling, in this preliminary communication, CD105 transfected rat myoblasts were utilized as an in vitro model. Overexpression of CD105 in these transfectants antagonised TGF-beta1-mediated inhibition of cell proliferation and reduced TGF-beta1-mediated p3TP-Lux (PAI-1 promoter) luciferase activity. It also reduced (CAGA)12-Luc luciferase activity in response to TGF-beta1. The CAGA sequence is specific for Smad3/4 binding, implying that CD105 is involved in inhibition of TGF-beta1/Smad3 signalling. Furthermore, CD105 overexpression reduced serine phosphorylation of Smad3 and inhibited subsequent nuclear translocation of Smad3. CD105 resulted in high phosphorylation of JNK1, which is able to activate c-Jun. c-Jun is known to inhibit Smad3 transcriptional activity on CAGA sites, suggesting that CD105 may also inhibit Smad3 signalling through JNK1.
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PMID:CD105 inhibits transforming growth factor-beta-Smad3 signalling. 1527 93

Transforming growth factor-beta (TGF-beta) signaling is facilitated by scaffold proteins such as SARA (Smad anchor for receptor activation). Endofin, a member of the FYVE domain protein family, has been suggested to regulate membrane trafficking. In this study, we report that endofin functions as a scaffold protein to facilitate TGF-beta signaling. Overexpression of endofin FYVE domain-deletion mutants inhibited TGF-beta-induced expression of CAGA-luciferase. Knockdown of endogenous endofin expression by RNA interference specifically led to reduction of the transcriptional responses of TGF-beta, but had no effect on BMP- or Wnt1-induced reporter expression. Furthermore, in endofin small interfering RNA-expressing stable cells, TGF-beta-mediated expression of plasminogen activator inhibitor-1 and p21(Cip1) was significantly reduced, and TGF-beta-promoted apoptosis was also impaired. We further showed that endofin could interact with Smad4 and TGF-beta type I receptors. Reduction of endogenous endofin expression resulted in a decrease of TGF-beta-induced Smad2 phosphorylation and Smad2-Smad4 complex formation. Together, our findings suggest that endofin facilitates TGF-beta signaling as a scaffold protein to promote the R-Smad-Smad4 complex formation by bringing Smad4 to the proximity of the receptor complex.
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PMID:Endofin, a FYVE domain protein, interacts with Smad4 and facilitates transforming growth factor-beta signaling. 1727 73

Oxidized low-density lipoprotein (Ox-LDL) activates transforming growth factor-beta (TGF-beta)/Smad signaling to stimulate plasminogen activator inhibitor-1 (PAI-1) expression in mesangial cells. Smad-binding sequences, termed CAGA boxes, are present in the promoter of human PAI-1 gene, and they mediate TGF-beta transcriptional induction. However, the functional role of each CAGA box in the Ox-LDL-induced PAI-1 promoter activation is unknown. In this study, mutation of 1 of the 3 CAGA boxes located at -730, -580, and -280 of the PAI-1 promoter decreased the Ox-LDL-induced luciferase activity by 40 to 58%, whereas mutations in 2 sites reduced it over 75% or completely abolished it. Overexpression of Smad3 in N-terminal tagged Smad3-transfected cells increased the Ox-LDL-induced transcriptional activation of the PAI-1 promoter, whereas mutation of Smad3 abolished it. Electrophoretic mobility shift assay showed that the labeled -280, -580, and -730 CAGA box probes detected DNA/protein complexes induced by Ox-LDL, whereas mutant probes did not. When nuclear extracts were preincubated with a 100-fold of an unlabeled -280, -580, and -730 CAGA oligonucleotide, the formation of complexes was prevented but not with mutant CAGA box competitors. The addition of anti-Smad3 to the reaction with the labeled -280 or -580 CAGA box probe resulted in a supershift, but not with the -730 CAGA box probe. These results suggest that the 3 CAGA elements in the PAI-1 promoter mediate the Ox-LDL-induced PAI-1 transcription to a different degree, of which the -280 and -580 CAGA regions directly bind to Smad3.
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PMID:Role of CAGA boxes in the plasminogen activator inhibitor-1 promoter in mediating oxidized low-density lipoprotein-induced transcriptional activation in mesangial cells. 1776 71


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