Purification and Characterization of a Naturally Occurring Vascular Endothelial Growth Factor · Placenta Growth Factor Heterodimer

Abstract

Vascular endothelial growth factor (VEGF) is a potent and selective mitogen for endothelial cells that is angiogenic in vivo and induced by hypoxia. A homologous protein, placenta growth factor (PlGF), is also reported to be mitogenic for endothelial cells in culture. The rat GS-9L glioma cell line produces not only VEGF homodimers but also PlGF homodimers and a novel heterodimer composed of VEGF and PlGF subunits. All three dimeric forms were purified to apparent homogeneity, and their structures and mitogenic activities were compared. VEGF.PlGF heterodimers are vascular endothelial cell mitogens nearly as potent as VEGF homodimers. Therefore, some of the biological activities attributed to VEGF homodimers might be mediated by VEGF.PlGF heterodimers. In contrast, pure PlGF homodimers are mitogenic for endothelial cells only at high, possibly non-physiologic concentrations; thus the biological relevance of their mitogenic activity for these cells is not obvious. However, the existence of not only homodimers but also heterodimers clearly extends the similarity between the VEGF/PlGF and the homologous platelet-derived growth factor systems.

PlGF: A Multitasking Cytokine with Disease-Restricted Activity

“…Furthermore, a PlGF variant, unable to bind FLT1 but still capable of heterodimerizing with VEGF, also inhibited VEGF-and PlGF-dependent angiogenesis in cancer (Tarallo et al 2010). It should be noted, however, that the precise role of the VEGF:PlGF heterodimers remains a matter of debate, as several other studies reported proangiogenic-not antiangiogenic-effects of these heterodimers in vitro and in vivo (DiSalvo et al 1995;Cao et al 1996a,b;Autiero et al 2003). So far, little/nearly nothing is known about the proangiogenic or antiangiogenic activity of naturally occurring VEGF:PlGF heterodimers in physiological settings in vivo.…”

The Carboxyl-terminal Domain(111–165) of Vascular Endothelial Growth Factor Is Critical for Its Mitogenic Potency

“…Interestingly, recent studies describing the existence of VEGF⅐PlGF heterodimers further extend the concept that structural heter- ogeneity may be responsible for a graded biological response. While the PlGF homodimer had minimal endothelial cell mitogenic activity compared to that of the VEGF homodimer, the heterodimer displayed intermediate activity (34). With respect to proteolytic digestion resulting in the generation of VEGF 110 from VEGF 165 or VEGF 189 , little is known at this time about the prevalence of this process in vivo.…”

The kallikrein-kinin system, but not vascular endothelial growth factor, plays a role in the increased vascular permeability associated with ovarian hyperstimulation syndrome

“…The amount of purified protein was determined using the Bio-Rad protein assay reagent (Bio-Rad, Hercules, CA, USA) with serially diluted BSA as standard (Conn et al 1990, Houck et al 1992, Disalvo et al 1995. Biological activity of this VEGF protein was demonstrated by competition with binding of recombinant 125 I-VEGF 165 to HUVECs and by its ability to stimulate proliferation of these cells (Nagy et al 1995).…”