ABSTRACT
The mechanisms of action of growth factors are very complex. The structural and functional effects of these extracellular signaling molecules are intimately related to molecular changes at different subcellular levels. 1,2 The responses of cells stimulated by growth factors comprise two sequential events: transductional and posttransductional. In turn, the transductional events consist of two sequential steps: binding of the signaling agent to a receptor on the cell surface and production or translocation of mediators (second messengers). In the posttransductional events, specific regulatory changes occur at different subcellular sites, including the plasma membrane, the cytoplasm, various cellular organelles, and the nucleus. Alterations in the regulation of gene expression frequently occur in cells stimulated with growth factors.
