Cell cycle-related changes in F-actin distribution are correlated with glycolytic activity.

XTH-2 cells, a cell line derived from tadpole heart endothelial cells, were blocked at the end of the G1 phase of the cell cycle using desoxyguanosine (dG). Stress fibers are the dominant actin fibril structure in blocked cells. They disappear starting with the release of the dG block until the G2 phase of the cell cycle. In addition, after the release peripheral lamellae and microspikes appear, indicating increased surface motility of the cells. Concomitantly with these changes, net lactic acid production is increased while oxygen consumption remains constant. Increase in the content of F-actin per cell takes place only in subconfluent cultures. Similar morphological changes (organization of F-actin) have been induced by phorbol myristate acetate treatment. These are also accompanied by an increase in lactic acid production and unaltered oxygen consumption. Therefore, the changes in energy metabolism are supposed to result from the rearrangement of the F-actin network: The emanating loose fibrillar pattern provides an increased surface for the association with glycolytic enzymes, which enhances enzyme activity and represents a more motile state. The increased energy demand of the more motile structures is supplied predominantly by ATP derived from glycolysis.