Compare and contrast the activation mechanisms for the epide

Compare and contrast the activation mechanisms for the epidermal growth factor receptor (EGF) and the growth hormone (GH) receptor.

Solution

A growth factor (GF) is a naturally occurring substance.

Usually it is a protein or a steroid hormone.

Growth factors for example cytokines and hormones are important for regulating a variety of cellular processes:

stimulating cellular growth

cell proliferation

cellular differentiation

A growth factor receptor is a receptor which binds to growth factor to start the signaling cascade for cell differentiation and proliferation.

The epidermal growth factor receptor (EGFR) belongs to the group of transmembrane proteins that mediate the actions of growth factors including EGF.

Mechanism:

Growth factors, which are ligands, bind to the receptor to form ligand- receptor complex which initiates the signal transduction cascade through autophosphorylation.

EGFRs are a family of tyrosine kinase receptors.

For the EGF receptor system, ligand binding induces homo- and heterodimerization of the receptor leading to activation of the intracellular tyrosine kinase.

The tyrosine kinase activity, in turn, initiates a signal transduction cascade that results in a variety of biochemical changes within the celllikeincreased glycolysis and protein synthesis. This increases expression of certain genes including the gene for EGFRwhich ultimately leads to DNA synthesis and cell proliferation.[10]

Second Messengers: Binding of hormone to receptor initiates a series of events leading to generation of second messengers.