Characterization of Heparin Affin Regulatory Peptide Signaling in Human Endothelial Cells

Abstract

Heparin affin regulatory peptide (HARP) is an 18-kDa secreted growth factor that has a high affinity for heparin and a potent role on tumor growth and angiogenesis. We have previously reported that HARP is mitogenic for different types of endothelial cells and also affects cell migration and differentiation (12). In this study we examined the signaling pathways involved in the migration and tube formation on matrigel of human umbilical vein endothelial cells (HUVEC) induced by HARP. We report for the first time that receptor-type protein-tyrosine phosphatase ␤/ (RPTP␤/), which is a receptor for HARP in neuronal cell types, is also expressed in HU-VEC. We also document that HARP signaling through RPTP␤/ leads to activation of Src kinase, focal adhesion kinase, phosphatidylinositol 3-kinase, and Erk1/2. Sodium orthovanadate, chondroitin sulfate-C, PP1, wortmannin, LY294002, and U0126 inhibit HARP-mediated signaling and HUVEC migration and tube formation. In addition, RPTP␤/ suppression using small interfering RNA technology interrupts intracellular signals and HUVEC migration and tube formation induced by HARP. These results establish the role of RPTP␤/ as a receptor of HARP in HUVEC and elucidate the HARP signaling pathway in endothelial cells.

Interplay between αvβ3 Integrin and Nucleolin Regulates Human Endothelial and Glioma Cell Migration

“…The present study shows that ERK 1 ⁄ 2 is not involved in PTN-induced cell surface NCL localization, although it is required for PTN-induced endothelial cell migration (26). One possible explanation is that ERK 1 ⁄ 2 may lay downstream of ␣ v ␤ 3 -mediated cell surface NCL localization.…”

“…To test the hypothesis that PTN-induced cell surface NCL localization depends on ␤ 3 Tyr 773 phosphorylation through RPTP␤/, down-regulation of RPTP␤/ expression in HUVEC by siRNA was performed as previously described (26), and inhibited PTN-induced cell surface NCL localization (Fig. 2E) Fig.…”

“…7). The latter has important roles in cell migration (41) and the remodeling of actin filaments induced by growth factors (42) and integrins (43), and is involved in PTN-induced endothelial cell migration (26). Both the regulation of nucleocytoplasmic shuttling of NCL by phosphorylation (44) and the reported physical interaction between NCL and PI3K (16,45), indicates a possible direct regulation of NCL by PI3K upon ␤ 3 Tyr 773 phosphorylation.…”

“…PTN binding to its receptor RPTP␤/ in endothelial cells leads to dephosphorylation and thus activation of c-Src (26), leading to Tyr 773 phosphorylation of ␤ 3 integrin and PTN-induced endothelial cell migration (24). Because both ␣ v ␤ 3 (24) and NCL (18) are required for PTN-induced cell migration, the aim of the present study was to investigate interplay between NCL and ␣ v ␤ 3 that regulates human endothelial and glioma cell migration.…”

Midkine Lacking Its Last 40 Amino Acids Acts on Endothelial and Neuroblastoma Tumor Cells and Inhibits Tumor Development

“…MDKD81-121 is able to reduce the formation of capillary-like structures, a crucial step in tumor neovascularization. The effects of MDKD81-121 on HUVEC could be mediated by the inhibition of ALK and/or RPTPb/z tyrosine kinase receptors as HUVECs have been shown to express MDK and both receptors (36,37) enabling the stimulation of the phosphorylation of ALK (36) and the activation of the Akt and ERK pathways (38). We also showed that MDKD81-121 inhibits endothelial cell cycling with a complete extinction of Ki67 expression, while promotes cell apoptosis via activation of a set of genes, including CHOP, implicated in ER stress-mediated apoptosis pathway.…”