Neuropilin-1 exerts co-receptor function for TGF-beta-1 on the membrane of cancer cells and enhances responses to both latent and active TGF-beta

Abstract

Neuropilin (Nrp)-1 and Nrp-2 are multifunctional proteins frequently expressed by cancer cells and contribute to tumor progression by mechanisms that are not well understood. They are co-receptors for vascular endothelial growth factor and class 3 semaphorins, but recently we found that Nrp1 also binds latent and active transforming growth factor (TGF)-β1, and activates the latent form latency-associated peptide (LAP)-TGF-β1. Here, we report that Nrp1 has affinity for TGF-β receptors TβRI and TβRII, the signaling TGF-β receptors, as well as TβRIII (betaglycan), as determined in binding assays, pull down assays and confocal microscopy. Nrp1 had a higher affinity for TβRI than TβRII and could form a complex with these receptors. In breast cancer cells, Nrp1 and TβRI cointernalized in the presence of TGF-β1. Nrp1 acted as a TGF-β co-receptor by augmenting canonical Smad2/3 signaling. Importantly, Nrp-positive cancer cells, unlike negative cells, were able to activate latent TGF-β1 and respond. We examined two other membrane proteins that bind LAP-TGF-β, i.e. an RGD-binding integrin (αvβ3) and Glycoprotein A repetitions predominant (CLRRC32). RGD-binding integrins are frequently expressed by cancer cells, and glycoprotein A repetitions predominant is expressed by activated regulatory T cells that appear linked to poor tumor immunity. In vitro, these receptors did not activate LAP-TGF-β1, but subsequent addition of Nrp1 activated the cytokine. Thus, Nrp1 might collaborate with other latent TGF-β receptors in TGF-β capture and activation. We also show that Nrp2 has activities similar to Nrp1. We conclude that Nrp1 is a co-receptor for TGF-β1 and augments responses to latent and active TGF-β. Since TGF-β promotes metastasis this is highly relevant to cancer biology.

LHX2 is a direct NF-κB target gene that promotes primary hair follicle placode down-growth

“…Another reason for lack of TGFβ2 activity in ΔN and Lhx2-KO mice might be loss of Nrp2 (neuropilin 2) expression in hair placodes of both mouse models. It was recently shown that neuropilins can activate the latent TGFβ complex (Glinka et al, 2011). Furthermore, neuropilins can act as co-receptors for TGFβ receptors and increase the response to latent and active TGFβ (Glinka et al, 2011).…”

“…It was recently shown that neuropilins can activate the latent TGFβ complex (Glinka et al, 2011). Furthermore, neuropilins can act as co-receptors for TGFβ receptors and increase the response to latent and active TGFβ (Glinka et al, 2011). In Lhx2-KO mice, Nrp2 mRNA expression was absent in the epidermis; however, it was still expressed in the dermal condensate, which may be sufficient to induce TGFβ signaling and placode down-growth when Lhx2-KO skin explants are treated with recombinant TGFβ2.…”

Signaling Receptors for TGF-β Family Members

“…In myofibroblasts and tumor cells, NRP1 has been shown to suppress Smad1, 5, and 8 phosphorylation, while enhancing Smad2 and 3 phosphorylation Glinka et al 2011). However, in endothelial cells, NRP1 decreases Smad2 and 3 phosphorylation, which suppresses the stalk cell phenotype and enhances the tip cell phenotype during sprouting angiogenesis (Aspalter et al 2015).…”

The role of the semaphorins in cancer

“…52 Similarly, neuropilin-2 interacts with the VEGF-C tyrosine-kinase receptor VEGFR-3 and is crucial for the transduction of VEGF-C induced pro-lymphangiogenic signals. 55,66,67 The neuropilins were found to form complexes and modulate signal transduction mediated by several additional receptors including TGFb receptors, 68 platelet derived growth factor (PDGF) receptors, 69 Neurotrophin receptors, 70 the epidermal growth factor (EGF) receptor 71 and the hepatocyte growth factor receptor 72 (Fig. 3).…”