HIP/RPL29 antagonizes VEGF and FGF2 stimulated angiogenesis by interfering with HS-dependent responses.
HIP/RPL29 is a heparan sulfate (HS) binding protein with diverse activities including modulation of heparanase (HPSE) activity. We examined HIP/RPL29's ability to modulate actions of HS-binding growth factors (HBGFs) in angiogenesis. Between 1 and 2.5 microg/ml (ca. 60-150 nM), HIP/RPL29 inhibited HBGF-stimulated endothelial cell tube formation. Aortic explant outgrowth also was inhibited, but at higher concentrations (40 microg/ml). At this concentration, HIP/RPL29 had no effect on HBGF-stimulated MAPK phosphorylation or VEGF-stimulated receptor-2 phosphorylation at site Y-996. Partial inhibition occurred at VEGF receptor-2 site Y951, associated with cell migration. HBGF displacement from HS-bearing perlecan domain I showed that HIP/RPL29 released 50% of bound HBGF at 20 microg/ml, a dose where endothelial tube formation is inhibited. Similar FGF2 release occurred at pH 5.0 and 7.0, conditions where HPSE is highly and residually active, respectively. We considered that HIP/RPL29 inhibits HPSE-dependent release of HS-bound HBGFs. At pH 5.0, release of soluble HS was inhibited by 64% at concentrations of 5 microg/ml and by 77% at 40 microg/ml, indicating that HIP/RPL29 antagonizes HPSE activity. At concentrations up to 40 microg/ml (ca. 2.5 microM) where angiogenic processes are inhibited, release of FGF2 occurred in the presence of HPSE and HIP/RPL29. The majority of this FGF2 is not bound to soluble HS. Studies of HIP/RPL29 binding to HS indicated that many structural features of HS are important in modulation of HBGF activities. Our findings suggest that inhibition of angiogenic processes by HIP/RPL29 involves attenuation of the formation of soluble, biologically active HBGF:HS complexes that activate HBGF receptors.
D'Souza
Sonia
S
Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.
Yang
Weidong
W
Marchetti
Dario
D
Muir
Caroline
C
Farach-Carson
Mary C
MC
Carson
Daniel D
DD
D001779:Blood Coagulation Factors / Q000378:metabolism*; D002478:Cells, Cultured; D016222:Fibroblast Growth Factor 2 / Q000037:antagonists & inhibitors*; D006497:Heparan Sulfate / Q000378:metabolism*; D006801:Humans; D018919:Neovascularization, Physiologic; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins / Q000378:metabolism; D012269:Ribosomal Proteins; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors*
D001779:Blood Coagulation Factors; D016222:Fibroblast Growth Factor 2; D006497:Heparan Sulfate; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D012269:Ribosomal Proteins; D042461:Vascular Endothelial Growth Factor A; C104946:RPL29 protein, human