title: Histidine-rich glycoprotein blocks collagen-binding integrins and adhesion of endothelial cells through low-affinity interaction with α2 integrin.
abstract: The plasma protein histidine-rich glycoprotein (HRG) affects the morphology and function of both endothelial cells (ECs) and monocytes/macrophages in cancer. Here, we examined the mechanism of action of HRG's effect on ECs. HRG suppressed adhesion, spreading and migration of ECs specifically on collagen I (COL I) whereas ECs seeded on other extracellular matrix proteins were insensitive to HRG. HRG did not bind specifically to COL I or to the α-integrin binding site on collagen, GFOGER. Furthermore, HRG's inhibition of EC adhesion was not dependent upon heparan sulfate (HS) moieties as heparitinase-treated ECs remained sensitive to HRG. C2C12 cells expressing α2 integrin, the major collagen-binding α-integrin subunit in ECs, showed increased binding of HRG compared with wild type C2C12 cells lacking the α2 subunit. Recombinant α2 I-domain protein bound HRG and to a higher extent when in active conformation. However, the α2 I-domain bound weakly to HRG compared with COL I and the purified α2β1 ectodomain complex failed to retain HRG. We conclude that HRG binds to α2 integrin through low-affinity interactions in a HS-independent manner, thereby blocking EC-adhesion to COL I.
authors.affiliation: Uppsala University, Department of Immunology, Genetics and Pathology, The Rudbeck Laboratory, Dag Hammarskjöldv. 20, 751 85 Uppsala, Sweden. Electronic address: frank.roche@igp.uu.se.
authors.forename: Francis
authors.initials: F
authors.lastname: Roche
authors.affiliation: University of Turku, Department of Biochemistry and MediCity Research Laboratory, FI-20014 Turku, Finland.
authors.forename: Kalle
authors.initials: K
authors.lastname: Sipilä
authors.affiliation: Uppsala University, Department of Immunology, Genetics and Pathology, The Rudbeck Laboratory, Dag Hammarskjöldv. 20, 751 85 Uppsala, Sweden.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Honjo
authors.affiliation: Uppsala University, Department of Medical Biochemistry and Microbiology, Biomedical Center, Box 582, 751 23 Uppsala, Sweden.
authors.forename: Staffan
authors.initials: S
authors.lastname: Johansson
authors.affiliation: Uppsala University, Department of Immunology, Genetics and Pathology, The Rudbeck Laboratory, Dag Hammarskjöldv. 20, 751 85 Uppsala, Sweden.
authors.forename: Sònia
authors.initials: S
authors.lastname: Tugues
authors.affiliation: University of Turku, Department of Biochemistry and MediCity Research Laboratory, FI-20014 Turku, Finland.
authors.forename: Jyrki
authors.initials: J
authors.lastname: Heino
authors.affiliation: Uppsala University, Department of Immunology, Genetics and Pathology, The Rudbeck Laboratory, Dag Hammarskjöldv. 20, 751 85 Uppsala, Sweden.
authors.forename: Lena
authors.initials: L
authors.lastname: Claesson-Welsh
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002460:Cell Line; D002633:Chemotaxis / Q000187:drug effects; D005260:Female; D015870:Gene Expression; D006497:Heparan Sulfate / Q000737:chemistry* / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D038982:Integrin alpha2beta1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D032446:Myoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology; D000099053:Histidine-Rich Glycoprotein
chemical_list: D006497:Heparan Sulfate; D038982:Integrin alpha2beta1; D021122:Protein Subunits; D011506:Proteins; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; D000099053:Histidine-Rich Glycoprotein; C467480:vascular endothelial growth factor A, mouse
keywords: Adhesion; Collagen; Endothelial cells; HRG; Integrin