Pro-angiogenic effects of pregnancy-specific glycoproteins in endothelial and extravillous trophoblast cells

Abstract

We previously reported that binding to heparan sulfate (HS) is required for the ability of the placentally-secreted pregnancy-specific glycoprotein 1 (PSG1) to induce endothelial tubulogenesis. PSG1 is composed of four immunoglobulin-like domains but which domains of the protein bind to HS remains unknown. To analyze the interaction of PSG1 with HS, we generated several recombinant proteins, including the individual domains, chimeric proteins between two PSG1 domains, and mutants. Using flow cytometric and surface plasmon resonance studies, we determined that the B2 domain of PSG1 binds to HS and that the positively charged amino acids encompassed between amino acids 43-59 are required for this interaction. Furthermore, we showed that the B2 domain of PSG1 is required for the increase in the formation of tubes by endothelial cells (EC) including a human endometrial EC line and two extravillous trophoblast (EVT) cell lines and for the pro-angiogenic activity of PSG1 observed in an aortic ring assay. PSG1 enhanced the migration of ECs while it increased the expression of matrix metalloproteinase-2 in EVTs, indicating that the pro-angiogenic effect of PSG1 on these two cell types may be mediated by different mechanisms. Despite differences in amino acid sequence, we observed that all human PSGs bound to HS proteoglycans and confirmed that at least two other members of the family, PSG6 and PSG9, induce tube formation. These findings contribute to a better understanding of the pro-angiogenic activity of human PSGs and strongly suggest conservation of this function among all PSG family members.

Roles of N-linked glycosylation and glycan-binding proteins in placentation: trophoblast infiltration, immunomodulation, angiogenesis, and pathophysiology

“…It possesses seven potential N-glycosylation sites of which at least four are substituted with N-glycans whose antennae are potential galectin ligands (complex N-glycan containing polylactosamines chains elongated moieties with mainly α2–3 sialic acid terminals, Figure 1A ) [ 95 ]. PSG1 not only interacts with α5β1 integrins to modulate EVT adhesion and migration [ 96 ], but performs its pro-angiogenic activity and immunomodulatory actions by binding to the latency-associated peptides of anti-inflammatory cytokines transforming growth factor-β1 and -β2, resulting in their activation and increasing the number of regulatory T cells [ 93 , 97 , 98 ]. Angiogenesis requires the remodeling of ECM through proteases such as MMPs.…”

“…In particular, the expression of MMP-2 and -9 by EVTs has been highlighted with respect to their ECM-remodeling function [ 99 , 100 ]. PSG1 also induces a higher expression of MMP-2 by HTR8/SVneo cells [ 93 ], suggesting a possible mechanism of PSG1-mediated angiogenesis.…”

Pregnancy-specific glycoproteins: evolution, expression, functions and disease associations

“…PSG1 binding to cell surface syndecans 1-4 and glypican-1 was detected in solid phase assays and using fluorescenceactivated cell sorting (FACS (Sulkowski et al 2011, Blois et al 2012. Binding of PSG1 to syndecans promotes proangiogenic endothelial tube formation (Lisboa et al 2011, Rattila et al 2020. In solid phase assays, the N1 domains of mouse PSG17, PSG22 and PSG23 also bind GAGs, which suggests conservation of a putative proangiogenic function between some human and mouse PSG family members (Sulkowski et al 2011, Blois et al 2012.…”

Medawar’s PostEra: Galectins Emerged as Key Players During Fetal-Maternal Glycoimmune Adaptation

“…Within the human PSGs, PSG1 is one of the highest expressed and the best studied (222,227,228). PSG1 has pro-angiogenic activity and immunomodulatory actions by binding to the latencyassociated peptides of the anti-inflammatory cytokines TGF-b1 and TGF-b2 resulting in their activation and increase in the number of T regulatory cells (229)(230)(231)(232). PSG1 also interacts with two integrins, a 5 b 1 and a IIb b 3 , resulting in its ability to modulate extravillous trophoblast adhesion and migration and the interaction of platelets with fibrinogen, respectively (221,227).…”