Growth factors: Growth factors are signaling molecules which bind specifically to the receptor molecule embedded in either the cytoplasm or   plasma membrane   or   nucleus   of a cell. The vast majority of receptors are activated by binding to secreted growth factors. Many growth factors, regulating development in multicellular organisms act at short range as in paracrine signaling or act where the cells can respond to substances that they themselves release as in case of autocrine signaling. For example, the insulin receptor binds insulin and related hormones called insulin-like growth factors 1 and 2.

Individual growth factor proteins tend to occur as members of larger families of structurally and   evolutionarily   related proteins. Few families of growth factors are listed below:

1. Epidermal growth factor   (EGF): Epidermal growth factor   is a   growth factor   that stimulates   cell growth,   proliferation and   differentiation   by binding to its receptor   EGFR. Human EGF is a 6045- Da   protein   with 53 amino acid residues   and three intramolecular   disulfide bonds.
   
2. Fibroblast growth factor   (FGF): Fibroblast growth factors are a family of growth factors   involved in   angiogenesis,   wound healing and embryonic development. The FGFs are   heparin-binding proteins and interactions with cell-surface-associated   heparan sulphate proteoglycans are essential for FGF   signal transduction. FGFs play an important role in the processes of proliferation and differentiation of wide variety of cells and tissues.
   
3. Insulin-like growth factor   (IGF): The   insulin-like growth factors   (IGFs) are   proteins   with high   sequence similarity   to   insulin. IGFs are part of a   complex system   that cells use to communicate with their   physiologic al   environment. This complex system consists of two   cell-surface receptors   (IGF1R and IGF2R), two   ligands   (IGF-1 and IGF-2), a family of six high-affinity   IGF-binding proteins   (IGFBP-1 to IGFBP-6), as well as associated IGFBP degrading   enzymes, referred to collectively as   proteases.

Role of growth factors in medicine:

Growth factors have been increasingly used in the treatment of   hematologic   and   oncologic diseases and cardiovascular diseases like leukemias, angiogenesis   for cardiovascular diseases, aplastic anaemia neutropenia, myelodysplastic syndrome   (MDS) and bone marrow   transplantation.

 

Interesting facts:

• The first hormone to be discovered is “Secretin”.
• William Bayliss (1860-1924) and Ernest Starling (1866-1927) discovered secretin in 1902.
• Glutamate is a positive autocrine signal for glucagon release.