title: Regulation of alpha5beta1 integrin conformation and function by urokinase receptor binding.
abstract: Urokinase-type plasminogen activator receptors (uPARs), up-regulated during tumor progression, associate with beta1 integrins, localizing urokinase to sites of cell attachment. Binding of uPAR to the beta-propeller of alpha3beta1 empowers vitronectin adhesion by this integrin. How uPAR modifies other beta1 integrins remains unknown. Using recombinant proteins, we found uPAR directly binds alpha5beta1 and rather than blocking, renders fibronectin (Fn) binding by alpha5beta1 Arg-Gly-Asp (RGD) resistant. This resulted from RGD-independent binding of alpha5beta1-uPAR to Fn type III repeats 12-15 in addition to type III repeats 9-11 bound by alpha5beta1. Suppression of endogenous uPAR by small interfering RNA in tumor cells promoted weaker, RGD-sensitive Fn adhesion and altered overall alpha5beta1 conformation. A beta1 peptide (res 224NLDSPEGGF232) that models near the known alpha-chain uPAR-binding region, or a beta1-chain Ser227Ala point mutation, abrogated effects of uPAR on alpha5beta1. Direct binding and regulation of alpha5beta1 by uPAR implies a modified "bent" integrin conformation can function in an alternative activation state with this and possibly other cis-acting membrane ligands.
authors.affiliation: Department of Medicine and Pulmonary and Critical Care Division, University of California, San Francisco, San Francisco, CA 94143, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wei
authors.forename: Ralf-Peter
authors.initials: RP
authors.lastname: Czekay
authors.forename: Liliane
authors.initials: L
authors.lastname: Robillard
authors.forename: Matthias C
authors.initials: MC
authors.lastname: Kugler
authors.forename: Feng
authors.initials: F
authors.lastname: Zhang
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Kim
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Xiong
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Humphries
authors.forename: Harold A
authors.initials: HA
authors.lastname: Chapman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D005109:Extracellular Matrix / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D039201:Integrin alpha3beta1 / Q000235:genetics / Q000378:metabolism; D039081:Integrin alpha5beta1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009842:Oligopeptides / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D017395:Plasminogen Activator Inhibitor 1 / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation; D034741:RNA, Small Interfering / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000378:metabolism; D018000:Receptors, Peptide / Q000378:metabolism; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins / Q000494:pharmacology; D016415:Sequence Alignment; D014568:Urokinase-Type Plasminogen Activator / Q000494:pharmacology
chemical_list: D005353:Fibronectins; D039201:Integrin alpha3beta1; D039081:Integrin alpha5beta1; D009842:Oligopeptides; C524898:PLAUR protein, human; D010455:Peptides; D017395:Plasminogen Activator Inhibitor 1; C524899:Plaur protein, mouse; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D018000:Receptors, Peptide; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins; C051382:arginyl-glycyl-aspartic acid directed cell adhesion receptor; C047981:arginyl-glycyl-aspartic acid; D014568:Urokinase-Type Plasminogen Activator