scholarly journals Cell Cycle Arrest by Transforming Growth Factor β1 near G1/S Is Mediated by Acute Abrogation of Prereplication Complex Activation Involving an Rb-MCM Interaction

2009 ◽  
Vol 30 (3) ◽  
pp. 845-856 ◽  
Author(s):  
Piyali Mukherjee ◽  
Sherry L. Winter ◽  
Mark G. Alexandrow
Keyword(s):  
Cell Cycle ◽  
Growth Factor ◽  
Transcriptional Control ◽  
Transforming Growth Factor ◽  
Direct Interaction ◽  
Transforming Growth Factor Β1 ◽  
S Phase ◽  
Mcm Helicase ◽  
Phase Entry ◽  
Tgf Β1

ABSTRACT Understanding inhibitory mechanisms of transforming growth factor β1 (TGF-β1) has provided insight into cell cycle regulation and how TGF-β1 sensitivity is lost during tumorigenesis. We show here that TGF-β1 utilizes a previously unknown mechanism targeting the function of prereplication complexes (pre-RCs) to acutely block S-phase entry when added to cells in late G1, after most G1 events have occurred. TGF-β1 treatment in early G1 suppresses Myc and CycE-Cdk2 and blocks pre-RC assembly. However, TGF-β1 treatment in late G1 acutely blocks S-phase entry by inhibiting activation of fully assembled pre-RCs, with arrest occurring prior to the helicase unwinding step at G1/S. This acute block by TGF-β1 requires the function of Rb in late G1 but does not involve Myc/CycE-Cdk2 suppression or transcriptional control. Instead, Rb mediates TGF-β1 late-G1 arrest by targeting the MCM helicase. Rb binds the MCM complex during late G1 via a direct interaction with Mcm7, and TGF-β1 blocks their dissociation at G1/S. Loss of Rb or overexpression of Mcm7 or its Rb-binding domain alone abrogates late-G1 arrest by TGF-β1. These results demonstrate that TGF-β1 acutely blocks entry into S phase by inhibiting pre-RC activation and suggest a novel role for Rb in mediating this effect of TGF-β1 through direct interaction with and control of the MCM helicase.

scholarly journals Transforming Growth Factor β1 Receptor II Is Downregulated by E1A in Adenovirus-Infected Cells

2003 ◽  
Vol 77 (17) ◽  
pp. 9324-9336 ◽  
Author(s):  
Vera L. Tarakanova ◽  
William S. M. Wold
Keyword(s):  
Cell Cycle ◽  
Growth Factor ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β1 ◽  
Protein Levels ◽  
Quiescent Cells ◽  
Growth Inhibitory ◽  
Infected Cells ◽  
Cycle Regulation ◽  
Tgf Β1

ABSTRACT Transforming growth factor β1 (TGF-β1) signaling is compromised in many tumors, thereby allowing the tumor to escape the growth-inhibitory and proapoptotic activities of the cytokine. Human adenoviruses interfere with a number of cellular pathways involved in cell cycle regulation and apoptosis, initially placing the cell in a “tumor-like” state by forcing quiescent cells into the cell cycle and also inhibiting apoptosis. We report that adenovirus-infected cells resemble tumor cells in that TGF-β1 signaling is inhibited. The levels of TGF-β1 receptor II (TβRII) in adenovirus-infected cells were decreased, and this decrease was mapped, by using virus mutants, to the E1A gene and to amino acids 2 to 36 and the C-terminal binding protein binding site in the E1A protein. The decrease in the TβRII protein was accompanied by a decrease in TβRII mRNA. The decrease in TβRII protein levels in adenovirus-infected cells was greater than the decrease in TβRII mRNA, suggesting that downregulation of the TβRII protein may occur through more than one mechanism. Surprisingly in this context, the half-lives of the TβRII protein in infected and uninfected cells were similar. TGF-β1 signaling was compromised in cells infected with wild-type adenovirus, as measured with 3TP-lux, a TGF-β-sensitive reporter plasmid expressing luciferase. Adenovirus mutants deficient in TβRII downregulation did not inhibit TGF-β1 signaling. TGF-β1 pretreatment reduced the relative abundance of adenovirus structural proteins in infected cells, an effect that was potentiated when cells were infected with mutants incapable of modulating the TGF-β signaling pathway. These results raise the possibility that inhibition of TGF-β signaling by E1A is a means by which adenovirus counters the antiviral defenses of the host.

scholarly journals Ligand-Independent Regulation of Transforming Growth Factor β1 Expression and Cell Cycle Progression by the Aryl Hydrocarbon Receptor

2007 ◽  
Vol 27 (17) ◽  
pp. 6127-6139 ◽  
Author(s):  
Xiaoqing Chang ◽  
Yunxia Fan ◽  
Saikumar Karyala ◽  
Sandy Schwemberger ◽  
Craig R. Tomlinson ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Growth Factor ◽  
Aryl Hydrocarbon Receptor ◽  
Rna Binding ◽  
Transforming Growth Factor ◽  
Kinase Inhibitor ◽  
Transforming Growth Factor Β1 ◽  
Cyclin Dependent Kinase ◽  
Aryl Hydrocarbon ◽  
Tgf Β1

ABSTRACT The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the toxic effects of its xenobiotic ligands and acts as an environmental checkpoint during the cell cycle. We expressed stably integrated, Tet-Off-regulated AHR variants in fibroblasts from AHR-null mice to further investigate the AHR role in cell cycle regulation. Ahr +/+ fibroblasts proliferated significantly faster than Ahr − / − fibroblasts did, and exposure to a prototypical AHR ligand or deletion of the ligand-binding domain did not change their proliferation rates, indicating that the AHR function in cell cycle was ligand independent. Growth-promoting genes, such as cyclin and cyclin-dependent kinase genes, were significantly down-regulated in Ahr − / − cells, whereas growth-arresting genes, such as the transforming growth factor β1 (TGF-β1) gene, extracellular matrix (ECM)-related genes, and cyclin-dependent kinase inhibitor genes, were up-regulated. Ahr − / − fibroblasts secreted significantly more TGF-β1 into the culture medium than Ahr +/+ fibroblasts did, and Ahr − / − showed increased levels of activated Smad4 and TGF-β1 mRNA. Inhibition of TGF-β1 signaling by overexpression of Smad7 reversed the proliferative and gene expression phenotype of Ahr − / − fibroblasts. Changes in TGF-β1 mRNA accumulation were due to stabilization resulting from decreased activity of TTP, the tristetraprolin RNA-binding protein responsible for mRNA destabilization through AU-rich motifs. These results show that the Ah receptor possesses interconnected intrinsic cellular functions, such as ECM formation, cell cycle control, and TGF-β1 regulation, that are independent of activation by either exogenous or endogenous ligands and that may play a crucial role during tumorigenesis.

scholarly journals Iron chelation-induced senescence-like growth arrest in hepatocyte cell lines: association of transforming growth factor β1 (TGF-β1)-mediated p27Kip1 expression

2002 ◽  
Vol 366 (2) ◽  
pp. 613-621 ◽  
Author(s):  
Gyesoon YOON ◽  
Hyun-Jung KIM ◽  
Young-Sil YOON ◽  
Hyeseong CHO ◽  
In K. LIM ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Growth Factor ◽  
Cell Lines ◽  
Cellular Proliferation ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β1 ◽  
G1 Arrest ◽  
Cyclin Dependent Kinase ◽  
Negative Cell ◽  
Tgf Β1

Iron is essential for cellular proliferation in all organisms. When deprived of iron, the growth of cells is invariably inhibited. However, the mechanism involved remains largely unclear. In the present study, we have observed that subcytotoxic concentrations of desferroxamine mesylate (DFO), an iron chelator, specifically inhibited the transition from G1 to S-phase of Chang cells, a hepatocyte cell line. This was accompanied by the appearance of senescent biomarkers, such as enlarged and flattened cell morphology, senescence-associated β-galactosidase activity and reduced expression of poly(ADP-ribose) polymerase. Concomitantly, p27Kip1 (where Kip is kinase-inhibitory protein) was induced markedly, whereas other negative cell-cycle regulators, such as p21Cip1 (where Cip is cyclin-dependent kinase-interacting protein), p15INK4B and p16INK4A (where INK is inhibitors of cyclin-dependent kinase 4), were not, implying its association in the G1 arrest. Furthermore, the induction of p27Kip1 was accompanied by an increased level of transforming growth factor β1 (TGF-β1) mRNA. When neutralized with an anti-(TGF-β1) antibody, p27Kip1 induction was completely abolished, indicating that TGF-β1 is the major inducer of p27Kip1. Finally, DFO-induced senescence-like arrest was found to be independent of p53, since cell-cycle arrest was still observed with two p53-negative cell lines, Huh7 and Hep3B cells. In conclusion, DFO induced senescence-like G1 arrest in hepatocyte cell lines and this was associated with the induction of p27Kip1 through TGF-β1, but was independent of p53.

scholarly journals JNK and p38 Inhibitors Prevent Transforming Growth Factor-β1-Induced Myofibroblast Transdifferentiation in Human Graves’ Orbital Fibroblasts

2021 ◽  
Vol 22 (6) ◽  
pp. 2952
Author(s):  
Tzu-Yu Hou ◽  
Shi-Bei Wu ◽  
Hui-Chuan Kau ◽  
Chieh-Chih Tsai
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor ◽  
Mapk Pathway ◽  
Transforming Growth Factor Β1 ◽  
Tissue Growth ◽  
Mitogen Activated Protein Kinase ◽  
Tissue Inhibitors Of Metalloproteinases ◽  
Western Blots ◽  
Orbital Fibroblasts ◽  
Tgf Β1

Transforming growth factor-β1 (TGF-β1)-induced myofibroblast transdifferentiation from orbital fibroblasts is known to dominate tissue remodeling and fibrosis in Graves’ ophthalmopathy (GO). However, the signaling pathways through which TGF-β1 activates Graves’ orbital fibroblasts remain unclear. This study investigated the role of the mitogen-activated protein kinase (MAPK) pathway in TGF-β1-induced myofibroblast transdifferentiation in human Graves’ orbital fibroblasts. The MAPK pathway was assessed by measuring the phosphorylation of p38, c-Jun N-terminal kinase (JNK), and extracellular-signal-regulated kinase (ERK) by Western blots. The expression of connective tissue growth factor (CTGF), α-smooth muscle actin (α-SMA), and fibronectin representing fibrogenesis was estimated. The activities of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) responsible for extracellular matrix (ECM) metabolism were analyzed. Specific pharmacologic kinase inhibitors were used to confirm the involvement of the MAPK pathway. After treatment with TGF-β1, the phosphorylation levels of p38 and JNK, but not ERK, were increased. CTGF, α-SMA, and fibronectin, as well as TIMP-1 and TIMP-3, were upregulated, whereas the activities of MMP-2/-9 were inhibited. The effects of TGF-β1 on the expression of these factors were eliminated by p38 and JNK inhibitors. The results suggested that TGF-β1 could induce myofibroblast transdifferentiation in human Graves’ orbital fibroblasts through the p38 and JNK pathways.

scholarly journals Transforming growth factor-β1-induced N-cadherin drives cell–cell communication through connexin43 in osteoblast lineage

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Yueyi Yang ◽  
Wenjing Liu ◽  
JieYa Wei ◽  
Yujia Cui ◽  
Demao Zhang ◽  
...  
Keyword(s):  
Growth Factor ◽  
Gap Junction ◽  
Cell Line ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β1 ◽  
Cx43 Expression ◽  
Mc3t3 Cell ◽  
Primary Osteoblasts ◽  
Tgf Β1 ◽  
Cell Cell

AbstractGap junction (GJ) has been indicated to have an intimate correlation with adhesion junction. However, the direct interaction between them partially remains elusive. In the current study, we aimed to elucidate the role of N-cadherin, one of the core components in adhesion junction, in mediating connexin 43, one of the functional constituents in gap junction, via transforming growth factor-β1(TGF-β1) induction in osteoblasts. We first elucidated the expressions of N-cadherin induced by TGF-β1 and also confirmed the upregulation of Cx43, and the enhancement of functional gap junctional intercellular communication (GJIC) triggered by TGF-β1 in both primary osteoblasts and MC3T3 cell line. Colocalization analysis and Co-IP experimentation showed that N-cadherin interacts with Cx43 at the site of cell–cell contact. Knockdown of N-cadherin by siRNA interference decreased the Cx43 expression and abolished the promoting effect of TGF-β1 on Cx43. Functional GJICs in living primary osteoblasts and MC3T3 cell line were also reduced. TGF-β1-induced increase in N-cadherin and Cx43 was via Smad3 activation, whereas knockdown of Smad3 signaling by using siRNA decreased the expressions of both N-cadherin and Cx43. Overall, these data indicate the direct interactions between N-cadherin and Cx43, and reveal the intervention of adhesion junction in functional gap junction in living osteoblasts.

scholarly journals Transforming Growth Factor β1 (TGF-β1) Promotes Endothelial Cell Survival during In Vitro Angiogenesis via an Autocrine Mechanism Implicating TGF-α Signaling

2001 ◽  
Vol 21 (21) ◽  
pp. 7218-7230 ◽  
Author(s):  
Francesc Viñals ◽  
Jacques Pouysségur
Keyword(s):  
Endothelial Cells ◽  
Growth Factor ◽  
Cell Survival ◽  
Network Formation ◽  
Egf Receptor ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β1 ◽  
In Vitro Angiogenesis ◽  
Tgf Β1

ABSTRACT Mouse capillary endothelial cells (1G11 cell line) embedded in type I collagen gels undergo in vitro angiogenesis. Cells rapidly reorganize and form capillary-like structures when stimulated with serum. Transforming growth factor β1 (TGF-β1) alone can substitute for serum and induce cell survival and tubular network formation. This TGF-β1-mediated angiogenic activity depends on phosphatidylinositol 3-kinase (PI3K) and p42/p44 mitogen-activated protein kinase (MAPK) signaling. We showed that specific inhibitors of either pathway (wortmannin, LY-294002, and PD-98059) all suppressed TGF-β1-induced angiogenesis mainly by compromising cell survival. We established that TGF-β1 stimulated the expression of TGF-α mRNA and protein, the tyrosine phosphorylation of a 170-kDa membrane protein representing the epidermal growth factor (EGF) receptor, and the delayed activation of PI3K/Akt and p42/p44 MAPK. Moreover, we showed that all these TGF-β1-mediated signaling events, including tubular network formation, were suppressed by incubating TGF-β1-stimulated endothelial cells with a soluble form of an EGF receptor (ErbB-1) or tyrphostin AG1478, a specific blocker of EGF receptor tyrosine kinase. Finally, addition of TGF-α alone poorly stimulated angiogenesis; however, by reducing cell death, it strongly potentiated the action of TGF-β1. We therefore propose that TGF-β1 promotes angiogenesis at least in part via the autocrine secretion of TGF-α, a cell survival growth factor, activating PI3K/Akt and p42/p44 MAPK.

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