title: Monoclonal antibody IAC-1 is specific for activated alpha2beta1 and binds to amino acids 199 to 201 of the integrin alpha2 I-domain.
abstract: In this study we describe the first monoclonal antibody, integrin activated conformation-1 (IAC-1), to recognize the active form of the platelet-collagen receptor, the integrin alpha(2)beta(1). IAC-1 has the following properties: (1) IAC-1 fails to bind to resting platelets but readily interacts with platelets stimulated by the glycoprotein VI-specific agonist, convulxin, and by other agonists; (2) similar concentration response relationships for binding of IAC-1 and soluble collagen were observed in convulxin-stimulated platelets; (3) the epitope for IAC-1 is T199Y200K201, which is located at the opposite site of the metal ion-dependent adhesion site in a region not involved in the I-domain "shifts" that occur upon ligand binding; (4) IAC-1 strongly binds to recombinant alpha(2) I-domain, therefore suggesting that the neo-epitope appears to be exposed by an "unmasking" of I-domain-covering regions upon activation; (5) IAC-1 binds to platelets during adhesion to collagen under shear conditions, demonstrating activation of alpha(2)beta(1); (6) as IAC-1 does not interfere with platelet-collagen binding, it defines a new class of antibodies that is distinct from those belonging to the "cation- and ligand-induced binding sites" (CLIBSs) and the "ligand mimetic" group. These characteristics make IAC-1 a very powerful tool to study alpha(2)beta(1) activation under dynamic and physiologically relevant conditions.
authors.affiliation: Laboratory for Thrombosis Research, IRC, K.U. Leuven Campus Kortrijk, E. Sabbelaan 53, B-8500 Kortrijk, Belgium. hans.deckmyn@kulak.ac.be
authors.forename: Anne
authors.initials: A
authors.lastname: Schoolmeester
authors.forename: Karen
authors.initials: K
authors.lastname: Vanhoorelbeke
authors.forename: Shinya
authors.initials: S
authors.lastname: Katsutani
authors.forename: Hilde
authors.initials: H
authors.lastname: Depraetere
authors.forename: Hendrik B
authors.initials: HB
authors.lastname: Feys
authors.forename: Johan M W
authors.initials: JM
authors.lastname: Heemskerk
authors.forename: Marc F
authors.initials: MF
authors.lastname: Hoylaerts
authors.forename: Hans
authors.initials: H
authors.lastname: Deckmyn
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D000918:Antibody Specificity; D001665:Binding Sites / Q000276:immunology; D001792:Blood Platelets / Q000276:immunology*; D002678:Chimera; D003094:Collagen / Q000378:metabolism; D003435:Crotalid Venoms / Q000494:pharmacology; D018604:Epitope Mapping; D006801:Humans; D038982:Integrin alpha2beta1 / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D037181:Lectins, C-Type; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D010973:Platelet Adhesiveness / Q000276:immunology; D017434:Protein Structure, Tertiary
chemical_list: D000911:Antibodies, Monoclonal; D003435:Crotalid Venoms; D038982:Integrin alpha2beta1; D037181:Lectins, C-Type; C028890:convulxin; D003094:Collagen