GROWTH-FACTORS IN THE EXTRACELLULAR-MATRIX

Much recent research has focused on the study of tile expression of gr owth factor genes and on the identification of growth factor signaling mechanisms inside cells, However, growth factor signaling can also be regulated outside of cells by extracellular matrix proteins and prote olytic enzymes, The ability of extracellular proteins to process compl ex information in the absence of new protein synthesis is illustrated ill blood clotting and complement pathways. An increasing number of gr owth factors, including IGFs, FGFs, TGF-P's, and HGF, have been found to associate,vith the extracellular matrix proteins or with heparan su lfate, Rapid and localized changes in the activity of these factors ca ll he induced by release from matrix storage and/or by activation of l atent forms, These growth factors, in turn, control cell proliferation , differentiation, and synthesis aad remodeling of the extracellular m atrix. It is therefore likely that much of the information processing necessary for construction of complex multicellular organisms occurs i n the extracellular environment, This suggests that extracellular matr ix plays a major role in the control of growth factor signaling.