Induction of glycolytic enzyme synthesis in proliferating fibroblasts. Study of phosphofructokinase, glucose phosphate isomerase and pyruvate kinase

Abstract

Specific activity of phosphofructokinase is 7-8-fold higher in exponentially growing human fibroblasts than in quiescent cells, but the difference is considerably less pronounced for two other glycolytic enzymes, glucose phosphate isomerase and pyruvate kinase. The ratio of the F-type to L-type phosphofructokinase subunits is essentially the same in growing and resting cells, 4:1. F-type-phosphofructokinase-related antigen concentration is decreased in resting cells as compared with proliferating fibroblasts, but relatively less than the enzyme activity; the ratio of the enzyme activity to the antigen concentration (immunological specific activity) is therefore lower in resting than in growing fibroblasts. Synthesis of phosphofructokinase, as a percentage of the total protein synthesis, is about 30-fold greater during the proliferative phase than in quiescent cells, but this difference is only 3-4-fold for glucose phosphate isomerase and pyruvate kinase. Modulation of the synthesis of phosphofructokinase therefore seems to be responsible for the changes of its specific activity in function of cell proliferation. The appearance of some inactive cross-reacting material in quiescent cells is probably due to post-translational alteration of the pre-synthesized molecules. Compared with other glycolytic enzymes, such as glucose phosphate isomerase and pyruvate kinase, phosphofructokinase seems to be the (or one of the) preferential target of glycolytic induction in proliferating cells.

Regulation of the multiple promoters of the human aldolase A gene: response of its two ubiquitous promoters to agents promoting cell proliferation

“…Migration products were blotted onto a nylon (gene screen-plus) membrane and hybridized with either a coding single-stranded probe complementary to the 5' extremity of exon Cl (A and D), with a probe complementary to exon N1 (B) or with a probe complementary to exon N2 ( C). RNAs from: adult skeletal muscle (2), fetal skeletal muscle (3), blood lymphocytes (4), adult heart (5), fetal heart (6), fetal lung (7), adult lung (8), fetal spleen (9), adult spleen (10), fetal adrenals (11), adult adrenals (12), Hep G2 cells deprivated of serum for one day (14), two days (15), three days (16), and Hep G2 cells stimulated by serum for 20 hours (17). Lanes 1 and 13 show size standards.…”

“…The expression of a great variety of genes can be induced when resting cells are stimulated either by serum or by other mitogenic agents, such as phorbol esters. Moreover, serum treament increases the level of several glycolytic enzymes quite before the onset of DNA synthesis (9,10,11). This has led us to examine whether, in cultured cells, the level of N or H aldolase A mRNAs was affected by serum or phorbol 12-myristate 13-acetate (PMA).…”