title: Neuropilin-1 is a receptor for transforming growth factor beta-1, activates its latent form, and promotes regulatory T cell activity.
abstract: Neuropilin-1 (Nrp1) is a multifunctional protein, identified principally as a receptor for the class 3 semaphorins and members of the vascular endothelial growth factor (VEGF) family, but it is capable of other interactions. It is a marker of regulatory T cells (Tr), which often carry Nrp1 and latency-associated peptide (LAP)-TGF-beta1 (the latent form). The signaling TGF-beta1 receptors bind only active TGF-beta1, and we hypothesized that Nrp1 binds the latent form. Indeed, we found that Nrp1 is a high-affinity receptor for latent and active TGF-beta1. Free LAP, LAP-TGF-beta1, and active TGF-beta1 all competed with VEGF165 for binding to Nrp1. LAP has a basic, arginine-rich C-terminal motif similar to VEGF and peptides that bind to the b1 domain of Nrp1. A C-terminal LAP peptide (QSSRHRR) bound to Nrp1 and inhibited the binding of VEGF and LAP-TGF-beta1. We also analyzed the effects of Nrp1/LAP-TGF-beta1 coexpression on T cell function. Compared with Nrp1(-) cells, sorted Nrp1+ T cells had a much greater capacity to capture LAP-TGF-beta1. Sorted Nrp1(-) T cells captured soluble Nrp1-Fc, and this increased their ability to capture LAP-TGF-beta1. Conventional CD4+CD25(-)Nrp1(-) T cells coated with Nrp1-Fc/LAP-TGF-beta1 acquired strong Tr activity. Moreover, LAP-TGF-beta was activated by Nrp1-Fc and also by a peptide of the b2 domain of Nrp1 (RKFK; similar to a thrombospondin-1 peptide). Breast cancer cells, which express Nrp1, also captured and activated LAP-TGF-beta1 in a Nrp1-dependent manner. Thus, Nrp1 is a receptor for TGF-beta1, activates its latent form, and is relevant to Tr activity and tumor biology.
authors.affiliation: Department of Laboratory Medicine, St. Michael's Hospital, 30 Bond Street, Room 2-013CC, Toronto, Ontario, Canada M5B 1W8. glinkay@smh.toronto.on.ca
authors.forename: Yelena
authors.initials: Y
authors.lastname: Glinka
authors.forename: Gérald J
authors.initials: GJ
authors.lastname: Prud'homme
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D039942:Neuropilin-1 / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D053773:Transforming Growth Factor beta1; D042461:Vascular Endothelial Growth Factor A; D039942:Neuropilin-1