A novel mechanism regulating growth factor association with the cell surface: identification of a PDGF retention domain.

Abstract

Platelet-derived growth factor (PDGF) chimeras were used to map a domain responsible for either efficient secretion of PDGF-A or the tight cell association of PDGF-B to their carboxy-terminal domains. Introduction of stop codons within PDGF-A or PDGF-B further dissected their respective carboxy-terminal domains. Although successive deletions of the PDGF-A carboxyl terminus did not impair its secretion, incremental deletions from the carboxyl terminus of PDGF-B abrogated its membrane retention properties and promoted secretion. By this approach, PDGF-B retention properties could be localized to PDGF-B residues 212-226. A processed form of PDGF-B, which contained this domain, was expressed at the cell surface but not released. Comparison of PDGF-B with PDGF-A revealed an analogous sequence located at the PDGF-A carboxylterminus. We demonstrated that this PDGF-A domain also acts as a retention sequence under conditions that inhibit its proteolytic cleavage. Thus, differences in PDGF-A and PDGF-B secretion relate to differential proteolytic processing of analogous retention domains. All of these findings establish a new mechanism for stable growth factor presentation at the cell surface.

The uPA/uPAR system regulates the bioavailability of PDGF-DD: implications for tumour growth

“…This finding was initially unexpected, as the PDGF-DD(GFD) more potently transformed NIH/3T3 cells in vitro. However, considering that altered pericellular retention and/or matrix interactions are important determinants for the physiological action of many other growth factors (LaRochelle et al, 1991;Ostman et al, 1991;Carmeliet et al, 1999;Grunstein et al, 2000;Lindblom et al, 2003;Lee et al, 2005), this could be a likely mechanism for controlling the function of PDGF-DD as well. In line with this, one could speculate that the observed differences in foci morphology induced by the two PDGF-DD forms are due to different spatial distribution, especially as we have previously shown that smaller and unevenly shaped foci can be formed from NIH/3T3 cells overexpressing matrix-bound PDGF-BB (Li et al, 2003).…”

Regulation of the stepwise proteolytic cleavage and secretion of PDGF-B by the proprotein convertases

“…In the blood vessel (BV) of a skin wound and atheromatous aorta, myofibroblasts (green arrow) PDGF-B and Furin were found to be expressed by different cells, suggesting a potential paracrine interaction 2002). This would result in the retention of the unprocessed and/or PC-cleaved form of PDGF-B at the cell surface, to be released in a controllable manner by a second processing event (LaRochelle et al, 1991;Andersson et al, 1994;Rolny et al, 2002). Conversely, several studies reported that deletion of the retention motif in PDGF-B leads to its increased secretion and accumulation in the cell culture media (LaRochelle et al, 1991;Andersson et al, 1994;Kaetzel et al, 1996).…”

“…This would result in the retention of the unprocessed and/or PC-cleaved form of PDGF-B at the cell surface, to be released in a controllable manner by a second processing event (LaRochelle et al, 1991;Andersson et al, 1994;Rolny et al, 2002). Conversely, several studies reported that deletion of the retention motif in PDGF-B leads to its increased secretion and accumulation in the cell culture media (LaRochelle et al, 1991;Andersson et al, 1994;Kaetzel et al, 1996). In addition, the reduced secretion of PDGF-B was previously reported to limit the action range of PDGF-B in vivo, as suggested from experiments with transplanted keratinocytes expressing wild-type or retention motiftruncated PDGF-B into athymic mice (Eming et al, 1999).…”

“…This includes an B24 kDa form retained intracellularly and degraded in lysosomes, a secreted B30 kDa form and an B40 kDa cell surface-associated form (Ostman et al, 1992). Using various PDGF chimeras, LaRochelle et al (1991) identified the C-terminal residues 212-226 of PDGF-B as the amino-acid sequence responsible for the retention properties of the surface-associated form of PDGF-B. The ratio of the various forms of PDGF-BB is likely to be dependent upon the activity of the proteases involved in PDGF-B processing.…”

Identification of three amino acid residues in the B‐chain of platelet‐derived growth factor with different importance for binding to PDGF α‐ and β‐receptors

“…The abilities of the mutant PDGF molecules to compete for binding of 12~I-PDGF-AA and 125I-PDGF-BB to a-and 13-receptors, respectively, were determined and compared to that of wild-type PDGF-BB. In order to achieve efficient secretion of wild-type PDGF-BB and PDGF-BB mutants, vector constructs were used coding for truncated molecules lacking the basic motif in the C-terminus of the PDGF B-chain which mediates retention intracellularly and to the extracellular matrix [15,20,21].…”