Kinetics of Early Changes in Phosphate and Uridine Transport and Cyclic AMP Levels Stimulated by Serum in Density-Inhibited 3T3 Cells

Asúa, Luis Jiménez de; Rozengurt, Enrique; Dulbecco, Renato

doi:10.1073/pnas.71.1.96

Cited by 86 publications

(4 citation statements)

References 13 publications

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“…Incorporation of [3H]uridine was in creased approximately twofold in the presence of serum, but the degree of inhibition by 60 ~tM DRB was unchanged (67%) and again complete and prompt reversal of the inhibition was obtained upon removal of DRB after a 60-rain period of treatment. Increased uptake of uridine upon addition of serum to confluent cultures of mouse 3T3 cells has been reported previously (4,5). The serum stimulation observed in the present study occurred in incomplete monolayers of L cells.…”

Section: Kineticssupporting

confidence: 86%

Action of dichlorobenzimidazole riboside on RNA synthesis in L-929 and HeLa cells.

Tamm¹,

Hand²,

Caliguiri³

1976

The Journal of Cell Biology

127

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A BSTR ACT 5,6-Dichloro-l-/~-o-ribofuranosylbenzimidazole (DRB) inhibits RNA synthesis in L-929 cells (mouse fibroblast line) and HeLa cells (human epithelioid carcinoma line) within 2 min of addition of the compound to the medium. By removing DRB from the medium, the inhibition is promptly and completely reversed after treatment of cells for as long as I h or even longer. The inhibitory effect of DRB on the overall rate of RNA synthesis is similar in L and HeLa ceils and is markedly concentration-dependent in the low dose range (5-20 #M or 1.6-6.4/~g/ml), but not at higher concentrations of DRB. At a concentration of 12 #M, DRB has a highly selective inhibitory effect on the synthesis of nuclear heterogeneous RNA in L cells. At higher concentrations, there is also inhibition of 45 S ribosomal precursor RNA synthesis, but at all concentrations the effect on heterogeneous RNA synthesis in L cells in considerably greater than that on preribosomal RNA synthesis. In HeLa cells, too, DRB has a selective effect on heterogeneous RNA synthesis, but quantitatively the selectivity of action is somewhat less pronounced. In both L and HeLa cells, the inhibition of synthesis of nuclear heterogeneous RNA is incomplete even at very high concentrations of DRB (150 ~zM). Thus, while DRB is a selective inhibitor of nuclear heterogeneous RNA synthesis, not all such RNA synthesis is sensitive to inhibition. It is proposed that messenger precursor RNA synthesis may largely be sensitive to inhibition by DRB. In short-term experiments, DRB has no effect on protein synthesis in L or HeLa cells. DRB has a slight to moderate inhibitory effect on uridine uptake into L cells and a moderate to marked effect on uptake of uridine into HeLa cells.

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Section: Kineticssupporting

confidence: 86%

Action of dichlorobenzimidazole riboside on RNA synthesis in L-929 and HeLa cells.

Tamm¹,

Hand²,

Caliguiri³

1976

The Journal of Cell Biology

127

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“…Certain effects of elevated Pi on cell behavior have been demonstrated to be cell autonomous. It was noted almost four decades ago that contact inhibited 3T3 cells respond to serum stimulation with a rapid increase in Pi transport (Cunningham and Pardee, 1969; de Asua et al, 1974; Barsh et al, 1977). Pi transport is regulated by a family of sodium dependent phosphate transporters (Werner et al, 1998; Collins et al, 2004; Tenenhouse, 2005).…”

mentioning

confidence: 99%

Is it the end of the line for the EMT?

Kisseleva

Brenner

2011

Hepatology

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E pithelial-to-mesenchymal transition (EMT) is an important biological concept that describes the reversible transition of differentiated epithelial cells into mesenchymal cells with increased motility and changes in gene expression. Three types of EMT have been proposed: Type 1 EMT describes the invasion of transition cells into the mesenchyme during development. Type 2 EMT describes the transition into mesenchymal cells, potentially including myofibroblasts during wound healing and repair. Type 3 EMT describes invasion of cancer cells, including those migrating into the circulation to generate distant metastases. 1Fibrosis studies conducted in different organs including the liver have demonstrated that myofibroblasts are the primary source of extracellular matrix.2 Myofibroblasts are immunophenotypically characterized by a stellate shape, expression of abundant pericellular matrix, and fibrotic genes (a-smooth muscle actin [a-SMA], nonmuscle myosin, fibronectin, vimentin).3 Ultrastructurally, myofibroblasts are defined by prominent rough endoplasmic reticulum, a Golgi apparatus producing collagen, peripheral myofilaments, fibronexus (no lamina), and gap junctions.3 Myofibroblasts are implicated in wound healing and fibroproliferative disorders. [4][5][6] In response to fibrogenic stimuli, such as transforming growth factor b1 (TGF-b1), myofibroblasts express a-SMA, secrete extracellular matrix (fibronectin, collagen type I and III), obtain high contractility, and change phenotype (production of the stress fibers). 7But where do these myofibroblasts come from? Hepatic stellate cells (HSCs) are considered to be a major source of fibrogenic myofibroblasts in the injured liver. Hepatic myofibroblasts may also originate from portal fibroblasts, 2 bone marrow-derived mesenchymal cells, and fibrocytes, 9,10 and by the transition of epithelial cells 11 and endothelial cells 12 to mesenchymal cells. What is the evidence for type 2 EMT being the etiology of the myofibroblasts in liver fibrosis? First, multiple studies in the kidney and in the lung were interpreted as showing EMT during fibrosis in those organs, and this concept was extrapolated to liver fibrosis (discussed in Zeisberg and Duffield 13 ). Second, primary cell culture studies have clearly demonstrated that cholangiocytes and hepatocytes undergo a change in the phenotype and gene expression toward a mesenchymal cell, especially after incubation with TGF-beta, which is the cytokine most closely associated with EMT.14 Third, immunohistochemical studies both in experimental and clinical liver fibrosis have reported the coexpression of mesenchymal markers (fibroblastspecific protein 1 [FSP1], a-SMA, vimentin, desmin) with the original epithelial markers (cytokeratin-19 for cholangiocytes and albumin for hepatocytes).15 These types of studies have been recently questioned, because the allegedly EMT-specific marker FSP1 (also called S100A4) has now been shown to be expressed by nonfibroblast cells in the liver, including by a subset of monocytes.16 Fourth, at lea...

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“…An early event during such activation with serum or insulin is the stimulation of uridine uptake [2]. Recent work has shown that it is not uridine transport but rather the subsequent trapping of uridine within the cell that is so enhanced [ 3 , 4 ] .…”

mentioning

confidence: 99%

Increase in the affinity of the uridine phosphorylation system for ATP after serum or insulin activation of 3T3 fibroblasts

Goldenberg

Stein

1978

J Supramol Struct

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The stimulation of uridine uptake, brought about by the addition of serum or insulin to quiescent 3T3 fibroblasts, is associated in the half-saturation concentration of the uridine phosphorylating system for the substrate ATP, with relatively little change in the maximum uptake or in the affinity for uridine. In stimulated cells the Km towards ATP fell in the range 0.053--0.187 mM, while V max was 34 to 52 pmoles/10(6) cells/min. In quiescent cells these values were 2.89--4.22 mM and 74.5--126 pmoles/10(6) cells/min, respectively. No difference was found, however, between the Km's for ATP when phosphorylation of uridine was determined using cell-free extracts prepared from either quiescent cells or from stimulated cells.

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Kinetics of Early Changes in Phosphate and Uridine Transport and Cyclic AMP Levels Stimulated by Serum in Density-Inhibited 3T3 Cells

Cited by 86 publications

References 13 publications

Action of dichlorobenzimidazole riboside on RNA synthesis in L-929 and HeLa cells.

Action of dichlorobenzimidazole riboside on RNA synthesis in L-929 and HeLa cells.

Is it the end of the line for the EMT?

Increase in the affinity of the uridine phosphorylation system for ATP after serum or insulin activation of 3T3 fibroblasts

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