One of the physiological responses activated by polypeptide growth factors is membrane ruffling. It is stimulated by growth factors if cells are kept in serum-free cultures, but also by the protein products of src and ras oncogenes under normal culture conditions where growth factors are available. Among the mechanisms activated by polypeptide growth factors is a pathway leading to protein kinase C. Protein kinase C modulates aspects of cell differentiation and, in the nervous system, memory.
C activates ruffling by an unknown mechanism.
Subsequent down-regulation of ruffling is accompanied by enhancement of filopodia formation. The relationship between these features suggests that they are mediated by GTPases, such as Cdc, or their effectors. How PKC changes the type of architecture at the cell edge is now under investigation. My group has investigated the physiological consequences of activating PKC, one of which is a change in the size or organization of the endosomal compartments. Since endosomes are loaded, in part, through ruffling activity, this feature may be dependent on increased ruffling.