title: A streptococcal collagen-like protein interacts with the alpha2beta1 integrin and induces intracellular signaling.
abstract: The streptococcal collagen-like proteins Scl1 and Scl2 are prokaryotic members of a large protein family with domains containing the repeating amino acid sequence (Gly-Xaa-Yaa)(n) that form a collagen-like triple-helical structure. Here, we test the hypothesis that Scl variant might interact with mammalian collagen-binding integrins. We show that the recombinant Scl protein p176 promotes adhesion and spreading of human lung fibroblast cells through an alpha2beta1 integrin-mediated interaction as shown in cell adhesion inhibition assays using anti-alpha2beta1 and anti-beta1 integrins monoclonal antibodies. Accordingly, C2C12 cells stably expressing alpha2beta1 integrin as the only collagen-binding integrin show productive cell adhesion activities on p176 that can be blocked by an anti-alpha2beta1 integrin antibody. In addition, p176 promotes tyrosine phosphorylation of p125(FAK) of C2C12 cells expressing alpha2beta1 integrin, whereas parental cells do not. Furthermore, C2C12 adhesion of human lung fibroblast cells to p176 induces phosphorylation of p125FAK, p130CAS, and p68Paxillin proteins. In a domain swapping experiment, we show that integrin binds to the collagenous domain of the Scl protein. Moreover, the recombinant inserted domain of the alpha2 integrin interacts with p176 with a relatively high affinity (K(D) = 17 nm). Attempts to identify the integrin sites in p176 suggest that more than one site may be involved. These studies, for the first time, suggest that the collagen-like proteins of prokaryotes retained not only structural but also functional characteristics of their eukaryotic counterparts.
authors.affiliation: Center for Extracellular Matrix Biology, Institute of Biosciences and Technology, Texas A&M University System Health Science Center, Houston, Texas 77030, USA.
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Humtsoe
authors.forename: Jiyeun K
authors.initials: JK
authors.lastname: Kim
authors.forename: Yi
authors.initials: Y
authors.lastname: Xu
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Keene
authors.forename: Magnus
authors.initials: M
authors.lastname: Höök
authors.forename: Slawomir
authors.initials: S
authors.lastname: Lukomski
authors.forename: Kishore K
authors.initials: KK
authors.lastname: Wary
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D001665:Binding Sites; D002448:Cell Adhesion / Q000502:physiology; D002478:Cells, Cultured; D003094:Collagen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D050719:Crk-Associated Substrate Protein; D003598:Cytoskeletal Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000737:chemistry / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D038982:Integrin alpha2beta1 / Q000235:genetics / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008168:Lung / Q000166:cytology; D051379:Mice; D008969:Molecular Sequence Data; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D050717:Retinoblastoma-Like Protein p130; D013297:Streptococcus pyogenes / Q000378:metabolism*
chemical_list: C493841:BCAR1 protein, human; D001426:Bacterial Proteins; C493842:Bcar1 protein, mouse; D050719:Crk-Associated Substrate Protein; D003598:Cytoskeletal Proteins; D038982:Integrin alpha2beta1; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; D020033:Protein Isoforms; D021122:Protein Subunits; D011506:Proteins; C496062:Pxn protein, mouse; D011994:Recombinant Proteins; D050717:Retinoblastoma-Like Protein p130; C423454:Scl1 protein, Streptococcus; C423453:Scl2 protein, Streptococcus; D003094:Collagen; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C496051:Ptk2 protein, mouse; D048031:JNK Mitogen-Activated Protein Kinases