In molecular biology
, Platelet-derived growth factor
) is one of the numerous growth factors
, or proteins
that regulate cell
growth and division
. In particular, it plays a significant role in blood vessel formation
(angiogenesis), the growth of blood vessels from already existing blood vessel tissue. Uncontrolled angiogenesis is a characteristic of cancer. Chemically Platelet-derived growth factor is dimeric glycoprotein
composed of two A or two B chains.
There are five different isoforms
of PDGF that activate cellular response through two different receptors
. Known ligands
include A (PDGFA
), B (PDGFB
), C (PDGFC
) and D (PDGFD
) and an AB heterodimer
and receptors alpha (PDGFRA
) and beta (PDGFRB
). PDGF has few other members of the family, for example VEGF sub-family
for PDGF, PDGFR
is classified as a receptor tyrosine kinase
(RTK), a type of cell surface
receptor. Two types of PDGFRs have been identified alpha type and beta type PDGFRs. The alpha type binds to PDGF-AA, PDGF-BB and PDGF-AB while the beta type PDGFR binds with high affinity to PDGF-BB and PDGF-AB.
PDGF binds to PDGFRs ligand binding pocket located within the second and third immunoglobulin domains. Upon activation by PDGF, these receptors dimerise, and are "switched on" by auto-phosphorylation
of several sites on their cytosolic
domains, which serve to mediate binding of cofactors and subsequently activate signal transduction
, for example, through the PI3K
pathway. Downstream effects of this include regulation of gene expression
and the cell cycle
The role of PI3K has been investigated by several laboratories. Accumulating data suggests that while this molecule is generally part of growth signaling complex, it plays a more profound role in controlling cell migration.
The different ligand isoforms have variable affinities for the receptor isoforms, and the receptor isoforms may variably form hetero- or homo- dimers. This leads to specificity of downstream signalling. It has been shown that the cis oncogene
is derived from the PDGF B-chain gene
. PDGF-BB is the highest-affinity ligand for the PDGFR-beta; PDGFR-beta is a key marker of hepatic stellate cell activation in the process of fibrogenesis
PDGF plays a role in embryonic
development, cell proliferation, cell migration, and angiogenesis
. PDGF has also been linked to several diseases
such as atherosclerosis
and malignant diseases.
In addition, PDGF is a required element in cellular division for fibroblast, a type of connective tissue cell. In essence, the PDGFs allow a cell to skip the G1 checkpoints in order to divide.
PDGF is also known to maintain proliferation of oligodendrocyte progenitor cells.
PDGF was one of the first growth factors
characterized, and has led to an understanding of the mechanism of many growth factor signaling pathways
Like many other growth factors that have been linked to disease, PDGF has provided a market for protein receptor antagonists
to treat disease. Such antagonists usually include specific antibodies
that target the molecule
of interest, which only act in a neutralizing manner.
However, recent developments have allowed some biotechnology companies to circumvent this problem by creating specialized molecules that not only bind the protein of interest, but also destroy it in an enzymatic fashion.
The "c-Sis" oncogene is derived from PDGF.