Acute activation of glucose uptake by glucose deprivation in L929 fibroblast cells

Glucose is a very important energy source for a wide variety of cells, and the ability of cells to respond to changes in glucose availability or other cell stresses is of critical importance. Many mammalian cells respond to acute stress by increasing the Vmax of transport through GLUT1; the most ubiquitously expressed glucose transporter isoform. This study investigated the acute response of glucose uptake to glucose deprivation in L929 fibroblast cells—a cell line that expresses only the GLUT1 transporter. Results indicated that glucose deprivation of only a minute activated glucose uptake 10-fold and reached a maximum of 20-fold within 10 min. The activation was dose dependent and only partially muted by addition of up to 20 mM pyruvate as an alternate energy source. In contrast to the kinetics of acute metabolic stress, glucose deprivation decreased the Km of transport, but did not alter the Vmax. Maximal activation of glucose transport by glucose deprivation was completely additive to activation of transport by methylene blue—a stimulant that increased the Vmax of transport without a change in the Km. Glucose-deprived activation of glucose transport was not inhibited by wortmannin or herbimycin A, but was completely inhibited by phenylarsine oxide. Altogether, the data indicate that L929 fibroblast cells respond quickly and robustly to the cell stress of glucose deprivation and methylene blue treatment by two distinct activation pathways.