Peptide Growth Factors

Abstract

Growth factors are secreted proteins that exert multiple effects on cell growth, metabolism, differentiation, and on the growth and development of organisms as diverse as flies, worms, frogs, and humans. Although the term growth factor was used initially to describe secreted substances that enhanced cell division, this phrase now includes peptides that stimulate or inhibit the progression of cells through mitosis, as well as proteins that act principally to regulate cellular differentiation. To accomplish these and other biological actions, growth factors activate specific cellular receptors. Receptors are modular proteins that can bind growth factors with high affinity and can transmit the information generated by binding into changes in cellular biochemistry. Growth factors also interact with other cell-associated or secreted binding proteins. In general, binding proteins do not mediate biological effects directly, but modulate growth factor availability. The interactions among these three components to regulate growth factor action are schematized in Fig. 1.