Cytokine stimulation of aerobic glycolysis in hematopoietic cells exceeds proliferative demand

Abstract

The relationship between growth factor-dependent cell growth and proliferation and the upregulation of cellular metabolism required to support these processes remains poorly defined. Here, we demonstrate that cell growth, proliferation, and glucose metabolism are coordinately regulated by interleukin-3 (IL-3) in cytokine-dependent cells. Surprisingly, glycolytic activity is stimulated to a greater extent than would be expected based on the rate of cell growth or proliferation. IL-3 signaling exerts a direct effect on glycolytic commitment independent of cell growth control. These results are not restricted to IL-3 as the cytokines IL-7 and IL-2 have similar effects on glucose metabolism when assayed in factor-dependent cell lines or primary lymphocytes, respectively. Growth factor stimulation leads cells to consume less oxygen and produce more lactate per glucose, indicative of conversion from oxidative to glycolytic metabolism. The enforced rate of glucose metabolism is in excess of that required to support cell growth; accordingly, if extracellular glucose is reduced, cells retain the ability to grow and proliferate by derepressing oxidative metabolism. These data suggest that the high rate of glycolysis observed in response to growth factor stimulation is a primary effect rather than a homeostatic response to increased cell growth.Keywords growth factor; interleukin-3; glucose metabolism; cell sizeThe growth, proliferation, and survival of cells within multicellular organisms depend on the presence of appropriate extracellular signals (1). These cues maintain the delicate balance between cell accumulation and cell death necessary for normal development and tissue homeostasis. These signals can arise from cellular interactions with soluble proteins such as cytokines, with other cells, or with the extracellular matrix. Extracellular signals that promote cell growth also result in increased glucose utilization. For example, early studies demonstrated that lectin stimulation of lymphocytes increased their glucose uptake, rate of glycolysis, and pentose phosphate shunt activity (2-4). Growth factor stimulated cell growth and proliferation result in the consumption of energy and macromolecular precursors, which might therefore stimulate glycolysis as a cellintrinsic response to a decline in an intracellular metabolic indicator such as ATP/ADP ratio, NADH/NAD + ratio, or mitochondrial membrane potential (3, 5). Bioenergetic demand can stimulate compensatory increases in glucose metabolism in specific settings. For instance, glycolytic rates rise in cells in which ATP consumption is increased or in which respiration is impaired (6-10). However, recent studies in our laboratory have indicated that growth factor signals serve to maintain levels of intracellular bioenergetic indicators such as ATP/ ADP, NADH/NAD + , and mitochondrial membrane potential (11,12). This suggested that receptors that promote cell growth might directly regulate the cellular uptake and utilization of essential nutrients, such as gluco...

Ceramide starves cells to death by downregulating nutrient transporter proteins

“…Growth factors not only block apoptosis, but also drive cellular bioenergetics. To evaluate whether altering the metabolic demand for nutrients affects ceramide sensitivity, we adapted FL5.12 cells to grow in high levels (500 pg/ml) or low levels (25 pg/ml) of IL-3, conditions that produce highly glycolytic or less nutrient-dependent cells, respectively (25,26). In keeping with a bioenergetic mechanism for ceramide-induced death, cells grown in low levels of IL-3 were much more resistant to ceramide than cells maintained in high levels of growth factors (Fig.…”

Genome-wide shRNA screen reveals increased mitochondrial dependence upon mTORC2 addiction

“…IL-3 increases glucose uptake and glycolysis such that energy production by glycolysis exceeds cellular needs (Bauer et al, 2004) which could explain the loss of mitochondrial dependence when cells proliferate in the presence of IL-3.…”

Analysis of the Major Patterns of B Cell Gene Expression Changes in Response to Short-Term Stimulation with 33 Single Ligands

“…The up-regulation of these glycolysis genes suggests that glycolysis activity increases and shifts toward the anaerobic pathway in B cells stimulated with ligands promoting cell growth and proliferation. In fact, several reports showed that lymphocyte cell lines and primary cells up-regulated the activity of multiple glycolysis enzymes including Hk2, and increased glycolysis rate and lactate production, when stimulated with cytokines or other mitogenic ligands such as anti-CD3 plus anti-CD28 (23,24). Although glycolysis is generally thought to be regulated by metabolic demands of the cells through feedback mechanisms, these recent reports suggest that glycolysis activity can be directly regulated by signal transduction pathways downstream of the receptors, such as the PI3K/protein kinase B (AKT) pathway (23,24).…”

“…In fact, several reports showed that lymphocyte cell lines and primary cells up-regulated the activity of multiple glycolysis enzymes including Hk2, and increased glycolysis rate and lactate production, when stimulated with cytokines or other mitogenic ligands such as anti-CD3 plus anti-CD28 (23,24). Although glycolysis is generally thought to be regulated by metabolic demands of the cells through feedback mechanisms, these recent reports suggest that glycolysis activity can be directly regulated by signal transduction pathways downstream of the receptors, such as the PI3K/protein kinase B (AKT) pathway (23,24). The shift toward anaerobic glycolysis is not because the cells lack the ability to undergo TCA cycle for maximal energy output, but rather is due to the fact that the rate of pyruvate and NADH generation from the high glycolysis activity and the ample supply of glucose in the culture medium exceeds the rate of their consumption in the mitochondria.…”

“…The shift toward anaerobic glycolysis is not because the cells lack the ability to undergo TCA cycle for maximal energy output, but rather is due to the fact that the rate of pyruvate and NADH generation from the high glycolysis activity and the ample supply of glucose in the culture medium exceeds the rate of their consumption in the mitochondria. As a result, pyruvate is reduced by NADH to lactate and secreted by the cells (23,24). In vivo when nutrients such as glucose are limited, the up-regulation of glycolysis by mitogenic signals can help stimulated B cells to mount rapid cell growth and proliferation and allow them an advantage in using nutrients over unstimulated cells.…”