Serum-dependent perinuclear accumulation of Cdc42 in mammalian cells.

Cdc42 is a member of the Rho family of GTPase. Cdc42 has been implicated to be involved in the movement, multiplication and transformation of mammalian cells by controlling the rearrangement of actin cytoskeleton and gene expression. But the mechanism of Cdc42 function has not yet been discovered. In this report we present data showing a perinuclear accumulation of Cdc42 in response to fetal bovine serum (FBS). There was no change in the amount of Cdc42 in response to FBS in the cell. It was found that protein component(s) of serum plays a major role in the perinuclear accumulation of Cdc42. Epidermal growth factor has also been found to stimulate the perinuclear accumulation of Cdc42 while NGF has no effect. Kinase inhibitors, quercetin and NDGA were found to block signals for the perinuclear accumulation of Cdc42. This suggests that phosphorylation of cellular proteins is essential for transducing signals generated from the serum component(s) to induce the perinuclear accumulation of Cdc42. These results indicate that redistribution of Cdc42 might be an important step in alteration of gene expression for controlling various functions of the cell including cell division.