Pollock, Richard Alan; (1992) Investigations into the function of structural isoforms of the platelet derived growth factor A-chain. Doctoral thesis (Ph.D), UCL (University College London).

Text Investigations_into_the_functi.pdf Download (11MB)

Abstract

Platelet derived growth factor (PDGF) is a covalent dimer of A and B chains with the structure AB, AA or BB depending on its source. The A and B chains are related but distinct polypeptides encoded by separate genes. PDGF-A can be differentially spliced, allowing production of two mature proteins one of which (PDGF-AL) is longer than the other (PDGF-AS) by 15 amino acids at its carboxyl terminus. PDGF-A homodimers are thought to be important in early development and, later, for regulating glial cell development in the central nervous system (CNS). In order to gain a clearer understanding of the role of PDGF in vivo it is important to define the functional significance of the different isoforms and their cellular sources and targets. This thesis describes my attempts to elucidate the functional differences between PDGF-AS and PDGF-AL and to determine whether they are differentially expressed in CNS derived tissues. To investigate the functional differences between PDGF-AS and PDGF-AL I introduced plasmid vectors directing the expression of the two isoforms into cultured Cos cells and subjected the expressed molecules to biochemical and immunocytochemical analysis. These studies provide evidence that PDGF-AS is secreted as a freely diffusible molecule while PDGF-AL is sequestered near the cells that produce it by binding to heparin-like molecules on the cell surface and in the extracellular matrix (ECM). The implications of these findings are discussed with reference to other factors that exist in different isoforms that are either freely diffusible or immobilised at the cell surface and within the ECM. I attempted to analyse the expression pattern in the CNS of the two isoforms by a combination of techniques, including SI nuclease protection, PCR amplification on reverse transcribed RNA, cDNA cloning and sequencing. These studies suggest that PDGF AS predominates in the tissues and cell types I have examined in agreement with other studies of a similar nature.

Download activity - last month

Export as CSVXMLJSON

Download activity - last 12 months

Export as JSONXMLCSV

Downloads by country - last 12 months

Export as XMLCSVJSON

Archive Staff Only

View Item