platelet-derived growth factor
(Science: growth factor) The major mitogen in serum for growth in culture of cells of connective tissue origin. It consists of 2 different but homologous polypeptides A and B (~30,000 D) linked by disulphide bonds. Believed to play a role in wound healing.
It is carried in the alpha-granules of platelets and is released when platelets adhere to traumatised tissues. Connective tissue cells near the traumatised region respond by initiating the process of replication.
The b chain is almost identical in sequence to p28sis, the transforming protein of simian sarcoma virus, that can transform only those cells that express receptors for platelet derived growth factor, suggesting that transformation is caused by autocrine stimulation. The receptor is a tyrosine kinase.