Phorbol 12,13‐dibutyrate and mitogens increase fructose 2,6‐bisphosphate in lymphocytes

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Abstract
The influence of tumour promoters and growth factors on glycolysis and on fructose‐2,6‐bisphosphate concentration was studied in isolated mouse spleen lymphocytes and in purified B‐cells. The intracellular concentration of fructose 2,6‐bisphosphate and the rate of lactate release were increased 2–3‐fold in spleen lymphocytes exposed to active phorbol esters, mitogenic lectins, interleukin 4 or lipopolysaccharide. The maximal effect was observed after 1 h of exposure. In these cells hexose 6‐phosphates increased 2‐fold and 6‐phosphofructo‐2‐kinase activity remained unchanged after treatment with phorbol 12,13‐dibutyrate or with lectins. Exposure of B‐cells to phorbol 12,13‐dibutyrate, interleukin 4 or lipopolysaccharide increased the glycolytic flux and the concentration of fructose 2,6‐bisphosphate without relation to their mitogenic activity.Lymphocytes and rat liver 6‐phosphofructo‐2‐kinase were partially purified using the same procedure. The lymphocyte enzyme was not inhibited by sn‐glycerol 3‐phosphate in contrast to the potent inhibition observed in liver. Treatment of both enzymes with the catalytic subunit of the cyclic‐AMP‐dependent protein kinase failed to inactivate 6‐phosphofructo‐2‐kinase from lymphocytes. These differences suggest that lymphocytes and liver contain different forms of this enzyme.