Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transforming growth factor-beta (TGF-beta), an ubiquitous regulatory peptide, has diverse effects on the differentiation and behavior of vascular smooth muscle cells (VSMC). However, the molecular mechanism through which TGF-alpha exerts its effects remains obscure. We investigated the phosphoinositide/protein kinase C [PKC] signaling pathway in the action of TGF-beta on cultured embryonic avian VSMC of differing lineage: a) thoracic aorta, derived from the neural crest; and b) abdominal aorta, derived from mesenchyme. The second messenger responsible for activation of PKC is sn-1,2-diacylglycerol [DAG]; TGF-beta increased the mass amounts of DAG in the membranes of neural crest-derived VSMC concurrent with translocation of PKC from the soluble to the membrane fraction, but TGF-beta had no effect on the DAG or PKC of mesenchyme-derived VSMC. TGF-beta potentiated the growth of platelet-derived growth factor (PDGF)-treated, neural crest-derived VSMC; but abolished PDGF-induced growth of mesenchymal cells. It is concluded that molecular and functional responses of VSMC to TGF-beta are heterogeneous and are functions of the embryonic lineage of the VSMC.
 ...
PMID:Transforming growth factor-beta: signal transduction via protein kinase C in cultured embryonic vascular smooth muscle cells. 844 47

Transforming growth factor alpha (TGF-alpha) is biosynthesized as a membrane-bound precursor protein, pro-TGF-alpha, that undergoes sequential endoproteolytic cleavages to release a soluble form of the factor. In the present study, we have analyzed the biosynthesis and regulation of TGF-alpha production in human tumor-derived cell lines that endogenously express pro-TGF-alpha and the epidermal growth factor (EGF) receptor. These cells biosynthesized membrane-anchored forms of the TGF-alpha that accumulated on the cell surface. Membrane-bound pro-TGF-alpha interacted with the EGF receptor, and complexes of receptor and pro-TGF-alpha contained tyrosine-phosphorylated receptor. Activation of the EGF receptor by soluble EGF or TGF-alpha had a dual effect on TGF-alpha production: an increase in pro-TGF-alpha mRNA levels and an increase in pro-TGF-alpha cleavage. These effects were largely prevented by preincubation with an anti-EGF receptor monoclonal antibody that blocked ligand binding. Growth factor autoinduction of cleavage could be stimulated by several second messenger pathways that are activated by the EGF receptor, including protein kinase C and intracellular calcium, and by other alternative mechanisms. EGF-stimulated cleavage of pro-TGF-alpha could be partially blocked by inhibition of these second messenger pathways. These results suggest that juxtacrine stimulation takes place in human tumor cells that coexpress both the EGF receptor and membrane-anchored TGF-alpha and that TGF-alpha is able to induce its own endoproteolytic cleavage by activating the EGF receptor.
 ...
PMID:Autocrine regulation of membrane transforming growth factor-alpha cleavage. 862 31

Although regulated ectodomain shedding is a well known process that affects a large group of transmembrane molecules, it is not clear how the shedding system selects its substrates. Here we investigate the structural requirements for the regulated shedding of two substrates of the general shedding system, the transforming growth factor-alpha precursor, pro-TGF-alpha, and the beta-amyloid precursor protein, beta-APP. The ability of different regions of pro-TGF-alpha or beta-APP to confer susceptibility to the shedding system was tested using as a reporter a transmembrane molecule that is not a substrate of this shedding system. For this purpose we chose the TGF-beta accessory receptor, betaglycan, since genetic and biochemical evidence showed that betaglycan is not a substrate of the shedding system. We determined that replacement of the 14 extracellular amino acids adjacent to the transmembrane region of betaglycan with the corresponding regions of TGF-alpha or beta-APP rendered betaglycan susceptible to ectodomain shedding. These domain swap constructs were cleaved in response to protein kinase C stimulation, and cleavage was prevented by the metalloprotease inhibitor TAPI, both effects being characteristic of the general shedding system. Domain swap constructs containing the transmembrane and/or the cytoplasmic domains of pro-TGF-alpha did not undergo regulated ectodomain cleavage. We conclude that despite a lack of sequence similarity, the extracellular regions of pro-TGF-alpha and beta-APP immediately preceding their transmembrane domains are key determinants of ectodomain shedding.
 ...
PMID:Role of the juxtamembrane domains of the transforming growth factor-alpha precursor and the beta-amyloid precursor protein in regulated ectodomain shedding. 920 36

Prolactin and prolactin agonists inhibited EGF-induced DNA synthesis in mammary epithelium, whereas other pituitary hormones had no effect on EGF-induced DNA synthesis. The inhibitory effect of prolactin was seen for EGF and TGF-alpha, but not for IGF-I or cholera toxin. Autoradiography indicated that prolactin decreased the ability of EGF to induce cells to progress to S phase of the cell cycle, and time course studies indicated that the effects of prolactin were not due to an altered timing of DNA synthesis induction. Prolactin addition within 30 min of adding EGF was necessary to inhibit EGF-induced DNA synthesis. Conditioned media from prolactin-treated cells from which prolactin had been neutralized with the extracellular domain of the prolactin receptor had no effect on EGF-induced DNA synthesis, suggesting that the effect was due to prolactin, not an autocrine factor induced by prolactin. Prolactin induced a rapid association of protein kinase C with the membrane fraction of NMuMG cells, as well as increased threonine phosphorylation of the EGF receptor. Protein kinase C inhibitors eliminated most of the inhibitory effect of prolactin on EGF-induced DNA synthesis. The protein kinase C inhibitor Calphostin C restored high-affinity EGF binding in prolactin-treated cells and reversed the inhibitory effect of prolactin on EGF-induced EGF receptor tyrosine phosphorylation.
 ...
PMID:Prolactin inhibits EGF-induced DNA synthesis in mammary epithelium via early signaling mechanisms: possible involvement of protein kinase C. 934 9

The hexosamine biosynthetic pathway has been hypothesized to be involved in the development of insulin resistance and diabetic vascular complications. In particular, it was demonstrated that hyperglycemia-induced production of transforming growth factor-beta (TGF-beta1), a prosclerotic cytokine causally involved in the development of diabetic nephropathy. Several lines of evidence indicate that TGF-beta1 induction is mediated by the hexosamine pathway. In cultured mesangial cells, high glucose levels induce TGF-beta1 production. This effect is eliminated by inhibition of glutamine: fructose-6-phosphate-amidotransferase (GFAT), the rate-limiting enzyme of this pathway. Furthermore, stable overexpression of GFAT increased levels of TGF-beta1 protein, mRNA, and promoter activity. Inasmuch as stimulation or inhibition of GFAT increased or decreased high glucose-stimulated activity of protein kinase C (PKC), respectively, the observed effects appear to be transduced by PKC. In similar experiments, involvement of the hexosamine pathway in hyperglycemia-induced production of cytokines (TGF-alpha and basic fibroblast growth factor [bFGF]) was demonstrated in vascular smooth muscle cells. These studies also revealed a rapid increase in GFAT activity by treatment with agents that elevated levels of cyclic adenosine 3',5' monophosphate (cAMP), thus indicating that GFAT activity is tightly regulated by cAMP-dependent phosphorylation. Using immunohistochemistry and in situ hybridization, high expression of GFAT was found in human adipocytes, skeletal muscle, vascular smooth muscle cells, and renal tubular epithelial cells. whereas glomerular cells remained essentially unstained. However, significant staining occurred in glomerular cells of patients with diabetic nephropathy. Current data indicate that the flux through the hexosamine pathway, regulated by GFAT, may be causally involved in the development of diabetic vascular disease, particularly diabetic nephropathy.
 ...
PMID:Role of the hexosamine biosynthetic pathway in diabetic nephropathy. 1099 85

Mucin production and secretion by specialized epithelial cells is a common mechanism used by mammals to protect the underlying mucosae against various injuries (pollutants, pathogens, pH). The expression of mucin genes is cell- and tissue-specific but is submitted to variations during cell differentiation, inflammatory process, and is altered during carcinogenesis. The molecular mechanisms responsible for the control of mucin transcription and expression are beginning to be understood as mucin gene promoters and regulatory regions are characterized. The four gel-forming mucin genes, MUC2-MUC5AC-MUC5B-MUC6, are clustered on the p15 arm of chromosome 11. Common regulatory mechanisms (PKA, PKC, PKG and Ca2+ signaling, Sp1/Sp3) may account for the capability of mucous-secreting cells to express several mucin genes simultaneously. In response to an insult or during carcinogenesis, the normal pattern of expression is altered and results from specific answers of the cell by activating different intracellular signaling pathways. 11p15 mucin genes are regulated at the transcriptional level by pro-inflammatory cytokines (IL-1beta, IL-6, TNF-alpha), pleiotropic cytokines (IL-4, IL-13, IL-9), bacterial exoproduct (LPS), growth factors (EGF, TGF-alpha), lipid mediator (PAF), retinoids and hormones. To date, the only downstream cascade known to activate mucin gene transcription is the Src/Ras/MAPK/pp90rsk cascade, which leads to the activation of the transcription factor NF-kappaB. Mucin gene transcription is also regulated by ATF-1, CREB and RAR-alpha transcription factors. Finally, repression of mucin transcription in cancer cells is under the control of the epigenetic mechanism of methylation. As transcriptional regulation of mucin genes begins to be unraveled, it becomes clear that many signaling pathways are involved. Our understanding of mucin gene transcriptional regulation, which awaits more data (identification of the signaling cascades and active cis-elements within promoters and introns), will most certainly lead to the use of mucin genes as molecular markers in cancer and molecular tools in human gene therapy, and to the synthesis of new therapeutic agents in inflammatory diseases of the epithelium.
 ...
PMID:Transcriptional regulation of the 11p15 mucin genes. Towards new biological tools in human therapy, in inflammatory diseases and cancer? 1157 73

Zinc-dependent metalloproteases can mediate the shedding of the extracellular domain of many unrelated transmembrane proteins from the cell surface. In most instances, this process, also known as ectodomain shedding, is regulated via protein kinase C (PKC). The tumor necrosis factor alpha-converting enzyme (TACE) was the first protease involved in regulated protein ectodomain shedding identified. Although TACE belongs to the family of metalloprotease-disintegrins, few members of this family have been shown to participate in regulated ectodomain shedding. In fact, the phenotype of tace-/- cells and that of Chinese hamster ovary cell mutants defective in ectodomain shedding points to the existence of a common PKC-activated ectodomain shedding system, whose proteolytic component is TACE, that acts on a variety of transmembrane proteins. Examples of these proteins include the Alzheimer's disease-related protein beta-amyloid precursor protein (betaAPP) and the transmembrane growth factors protransforming growth factor-alpha (pro-TGF-alpha) and, as shown in this report, proheparin-binding epidermal growth factor-like growth factor (pro-HB-EGF). Here we show that the mercurial compound 4-aminophenylmercuric acetate (APMA), frequently used to activate in vitro recombinant matrix metalloproteases, is an activator of the shedding of betaAPP, pro-HB-EGF, and pro-TGF-alpha. Treatment of tace-/- cells or Chinese hamster ovary shedding-defective mutants with APMA activates the cleavage of pro-TGF-alpha but not that of pro-HB-EGF or betaAPP, indicating that APMA activates TACE and also a previously unacknowledged proteolytic activity specific for pro-TGF-alpha. Characterization of this proteolytic activity indicates that it acts on pro-TGF-alpha located at the cell surface and that it is a metalloprotease active in cells defective in furin activity. In summary, treatment of shedding-defective cell lines with APMA unveils the existence of a metalloprotease activity alternative to TACE with the ability to specifically shed the ectodomain of pro-TGF-alpha.
 ...
PMID:Metalloprotease-dependent protransforming growth factor-alpha ectodomain shedding in the absence of tumor necrosis factor-alpha-converting enzyme. 1160 Apr 92

Tamoxifen (TAM) is a well-tolerated compound in the treatment of breast cancer and is primarily considered to act by competition with estrogen receptors (ER). Here we investigated the in vitro efficacy and potentially underlying mechanisms of TAM in established cell lines of squamous cell carcinomas of the head and neck (SCCHN). Using proliferation and apoptosis assays the antitumor activity of TAM in five SCCHN and the breast carcinoma line MCF-7 (positive control) was determined. MCF-7 was more sensitive to low-dose TAM (below 1 microM), whereas SCCHN showed significant growth inhibition at higher TAM concentrations (5-10 microM). Growth curve analysis and apoptosis assays were indicative for a cytostatic effect of low-dose TAM and high-dose TAM led to cell loss by apoptosis in sensitive SCCHN. In order to further characterize the observed antitumor effects we determined the amount of steroid hormone receptors with the dextran-coated charcoal method and immunocytochemistry. In addition, production of transforming growth factor (TGF-)-alpha, -beta1 and -beta2 was measured by ELISA, and protein kinase C (PKC) activity was assessed with a radioligand assay. Except MCF-7, none of the SCCHN lines was positive for ER. TAM caused decreased TGF-alpha and increased TGF-beta levels in MCF-7, but not in SCCHN supernatants. Furthermore, the antiestrogen reduced PKC activity in MCF-7, but not in SCCHN. In the present in vitro system, the observed antitumor activity of high-dose TAM in SCCHN cannot be explained by estrogen antagonism, alterations of TGF-alpha/beta levels or decreased PKC activity.
 ...
PMID:Effects of tamoxifen on human squamous cell carcinoma lines of the head and neck. 1204 64

Vascular endothelial growth factor (VEGF) is a major agent in choroidal and retinal neovascularization, events associated with age-related macular degeneration (AMD) and diabetic retinopathy. Retinal pigment epithelium (RPE), strategically located between retina and choroid, plays a critical role in retinal disorders. We have examined the effects of various growth factors on the expression and secretion of VEGF by human retinal pigment epithelial cell cultures (HRPE). RT-PCR analyses revealed the presence of three isoforms of mRNA corresponding to VEGF 121, 165, and 189 that were up regulated by TGF-beta1. TGF-beta1, beta2, and beta3 were the potent inducers of VEGF secretion by HRPE cells whereas bFGF, PDGF, TGF-alpha, and GM-CSF had no effects. TGF-beta receptor type II antibody significantly reversed induction of VEGF secretion by TGF-beta. In contrast activin, inhibin and BMP, members of TGF-beta super family, had no effects on VEGF expression in HRPE. VEGF mRNA levels and protein secretion induced by TGF-beta were significantly inhibited by SB203580 and U0126, inhibitors of MAP kinases, but not by staurosporine and PDTC, protein kinase C and NF-kappaB pathway inhibitors, respectively. TGF-beta also induced VEGF expression by fibroblasts derived from human choroid of eye. TGF-beta induction of VEGF secretion by RPE and choroid cells may play a significant role in choroidal neovascularization (CNV) in AMD. Since the secretion of VEGF by HRPE is regulated by MAP kinase pathways, MAP kinase inhibitors may have potential use as therapeutic agents for CNV in AMD.
 ...
PMID:Transforming growth factor-beta induces expression of vascular endothelial growth factor in human retinal pigment epithelial cells: involvement of mitogen-activated protein kinases. 1456 75

Replacement of damaged cells is a promising approach for treatment of age-related macular degeneration (AMD) and retinitis pigmentosa (RP); however, availability of donor tissue for transplantation remains a major obstacle. Key factors for successful engineering of a tissue include the identification of a neural cell line that is: homogeneous but can be expanded to give rise to multiple cells types; is nontumorigenic, yet capable of secreting neurotrophic factors; and is able to form three-dimensional (3D), differentiated structures. The goal of this study was to test the feasibility of tissue engineering from a multipotential human retinal cell line using a NASA-developed bioreactor. A multipotential human retinal precursor cell line was used to generate 3D structures. In addition, retinal pigment epithelium (RPE) cells were cocultured with neural cells to determine if 3D retinal structures could be generated in the bioreactor with cells grown on laminin-coated cytodex 3 beads. Cell growth, morphology, and differentiation were monitored by light and scanning electron microscopy, Western blot analysis, and analysis of glucose use and lactate production. The neuronal retinal precursor cell line cultured in a bioreactor gave rise to most retinal cell types seen in monolayer culture. They formed composite structures with cell-covered beads associated with one another in a tissue-like array. The beginning of layering and/or separation of cell types was observed. The neuronal cell types previously seen in monolayer cultures were also seen in the bioreactor. Some of the retinal cells differentiate into photoreceptors in the bioreactor with well-developed outer segment-like structures, a process that is critical for retinal function. Moreover, the neuronal cells that were generated resembled their in vivo phenotype more closely than those grown under other conditions. Outer segments were almost never seen in the monolayer cultures, even in the presence of photoreceptor-inducing growth factors such as basic fibroblast growth factor (bFGF) and transforming growth factor (TGF-alpha). Muller cells were occasionally seen when retinal, RPE cells were cocultured with retinal cells in the bioreactor. These have never been seen in this retinal cell line before. Cells grown in the bioreactor expressed several proteins specific for the retinal cell types: opsin, protein kinase C-alpha, dopamine receptor D4, tyrosine hydroxylase, and calbindin.
 ...
PMID:Generation of 3D retina-like structures from a human retinal cell line in a NASA bioreactor. 1465 19


<< Previous 1 2 3 4 Next >>