Galectin-8 interacts with podoplanin and modulates lymphatic endothelial cell functions

Abstract

Podoplanin is a small, mucin-like membrane glycoprotein highly expressed by lymphatic but not by blood vascular endothelial cells. Although it was shown to be indispensable for the correct formation and function of the lymphatic vasculature, its precise molecular function has remained unknown. In the present study, we identified the mammalian lectin galectin-8 as a novel, glycosylation-dependent interaction partner of podoplanin. Galectin-8 is a tandem-repeat type galectin, which interacts with cell surface glycoproteins, including certain integrins, as well as with extracellular matrix molecules such as fibronectin. Here we show that, similar to podoplanin, galectin-8 is more highly expressed by lymphatic than by blood vascular endothelial cells, and that it promotes lymphatic endothelial cell adhesion as well as haptotactic migration when immobilized onto a surface, while inhibiting the formation of tube-like structures by lymphatic endothelial cells in a collagen matrix when incorporated into the matrix. Importantly, functions of blood vascular endothelial cells, which lack podoplanin expression, are not affected by galectin-8. These data suggest a role for galectin-8 and podoplanin in supporting the connection of the lymphatic endothelium to the surrounding extracellular matrix, most likely in cooperation with other glycoproteins on the surface of lymphatic endothelial cells.

Podoplanin negatively regulates CD4+ effector T cell responses

“…Based on this information, it is tempting to speculate that the interaction of PDPN + T cells with CLEC-2 + cells might lead to T cell inhibition. However, we cannot exclude the possibility that galectin-8, a tandem-repeat type lectin, which is ubiquitously expressed by both hematopoietic and nonhematopoietic cells, may also play a role in PDPN-mediated T cell inhibition, particularly since several other galectin family members have been associated with T cell inhibition (23,27). Finally, the chemokine CCL21 is critical for organizing lymph node structure and potentially also ectopic lymphoid structures, as it guides dendritic cells and lymphocytes toward the T cell zone (28).…”

“…Thus, pure Th17 cells seem to create a special tissue microenvironment conducive to eLF formation, and, consequently, different ligands may be expressed in "Th17-adoptive-transfer-EAE" compared with "active EAE." PDPN has 3 known ligands: CLEC-2 (22), galectin-8 (23), and the chemokine CCL21 (24). Expression of CLEC-2 is largely restricted to hematopoietic cells, including platelets, DCs (25), and B cells (26).…”

Mutation of Threonine 34 in Mouse Podoplanin-Fc Reduces CLEC-2 Binding and Toxicity in Vivo While Retaining Anti-lymphangiogenic Activity

“…Recombinant proteins used in this study were produced either from the polyclonal population or from selected clones. Purification was performed using Protein A columns (Bio-Rad) as previously described (9).…”

DeepCAGE transcriptomics identify HOXD10 as a transcription factor regulating lymphatic endothelial responses to VEGF-C

“…Tubular morphogenesis assays were performed essentially as described previously (Cueni and Detmar, 2009). In brief, LECs were seeded on collagen-coated 24-well plates (8×10 4 /well) and grown to confluency.…”