Sugar Transport in Normal and Rous Sarcoma Virus-Transformed Chick-Embryo Fibroblasts

Abstract

ABSTRACT3-O-methylglucose (3-OMeG) is a nonmetabolizable glucose analog and is, therefore, suitable for transport studies. 3-OMeG and glucose compete for entry into normal and Rous sarcoma virus (RSV)-transformed chick-embryo fibroblasts. Therefore, 3-OMeG can be used to study the transport of glucose in these cells. Chickembryo fibroblasts infected and transformed by RSV take up 3-OMeG at a faster rate than uninfected cells when both cell types are growing at the same rate. The rate of efflux of 3-OMeG also increases after transformation. When the uptake and the efflux reach a steady state, the intracellular concentration of 3-OMeG is equal to the concentration in the medium. This finding indicates that glucose is transported across the plasma membrane by facilitated diffusion. The V. of the transport system for 3-OMeG increases after transformation, while the affinity or Km of the system remains unchanged. We conclude that viral transformation causes a change in the plasma membrane of the infected cells by increasing either the number of molecules or the mobility of the glucose carrier.Avian or mammalian cells can be transformed in vitro by RNA tumor viruses. The transformed cells are characterized by altered morphology, random orientation, and release from density-dependent inhibition (1). One of the earliest manifestations of the transformation is an increased rate of glucose accumulation inside the cells (2, 3).Temperature-sensitive mutants of Rous sarcoma virus (RSV) have been isolated (3-5). These mutants transform chick-embryo fibroblasts (CK) only at low temperature (36°), while they can infect and replicate at both high (410) and low temperatures. Thus, it is possible to distinguish between early and late events of the infection-transformation process because transformation can be initiated synchronously in the whole cell population simply by shifting the temperature of cells infected at 41°-36°.We studied (2) the rate of 2-deoxy-D-glucose (2-dOG) accumulation inside chick-embryo fibroblasts infected with one of the mutants described above, T5 (4). 2-deoxy-D-glucose is a glucose analog that is taken up and phosphorylated by the cell, but is not further metabolized (6, 7). 2-dOG and glucose compete with one another in normal and RSV-transformed chick-embryo fibroblasts, CK(RSV) (Venuta, unpublished).

Cell shape and hexose transport in normal and virus‐transformed cells in culture

“…3) Both CB and phloretin were shown to trap the sugar within the cell (data not shown). The water space was calculated (14) from the plateau for 3MG uptake, assuming that at equilibrium intracellular and extracellular concentrations were similar (8,9) and is shown in Table I.…”

Glucose Transport across the Blood—Brain Barrier in Normal Human Subjects and Patients with Cerebral Tumours Studied Using [11C]3-O-Methyl-D-Glucose and Positron Emission Tomography

“…Hatanaka et al (1970) have shown that mouse cells, when transformed with murine sarcoma virus, have an increased V max and decreased Km for 2-DG influx. Chick embryo fibroblasts transformed with Rous sarcoma virus show both an increased influx and efflux of MeG, attributable to increases in V max for this tracer (Venuta and Rubin, 1973;Weber, 1973). This increased transport of o-glucose analogues into cultured tumour cells parallels the increased level of aerobic glycolysis that has been docu mented in both animal and human tumour studies (Warburg, 1956;Sweeney et aI.…”

“…Second it was desired to study [IIC]MeG uptake by gliomas, as tissue cul ture studies have shown increased levels of MeG and 2-DG transport into isolated tumour cells (Ha tanaka et aI., 1970;Venuta and Rubin, 1973;Weber 1973). Third it was desired to study the effect of cerebral tumours on [llC]MeG transport into con tralateral cortical tissue.…”

Growth- and Density-Dependent Inhibition of Deoxyglucose Transport in Balb 3T3 Cells and Its Absence in Cells Transformed by Murine Sarcoma Virus

“…In such serum-starved sparse cultures, intracellular cAMP reaches a high level, characteristic of density-inhibited cultures (14). (20). Density-dependent inhibition of hexose uptake by uninfected cultures of chick-embryo fibroblasts and its stimulation by serum, trypsin, neuraminidase, and insulin have been reported (4,12).…”