title: Characterization of integrin-tetraspanin adhesion complexes: role of tetraspanins in integrin signaling.
abstract: Tetraspanins (or proteins from the transmembrane 4 superfamily, TM4SF) form membrane complexes with integrin receptors and are implicated in integrin-mediated cell migration. Here we characterized cellular localization, structural composition, and signaling properties of alpha3beta1-TM4SF adhesion complexes. Double-immunofluorescence staining showed that various TM4SF proteins, including CD9, CD63, CD81, CD82, and CD151 are colocalized within dot-like structures that are particularly abundant at the cell periphery. Differential extraction in conjunction with chemical cross-linking indicated that the cell surface fraction of alpha3beta1-TM4SF protein complexes may not be directly linked to the cytoskeleton. However, in cells treated with cytochalasin B alpha3beta1-TM4SF protein complexes are relocated into intracellular vesicles suggesting that actin cytoskeleton plays an important role in the distribution of tetraspanins into adhesion structures. Talin and MARCKS are partially codistributed with TM4SF proteins, whereas vinculin is not detected within the tetraspanin-containing adhesion structures. Attachment of serum-starved cells to the immobilized anti-TM4SF mAbs induced dephosphorylation of focal adhesion kinase (FAK). On the other hand, clustering of tetraspanins in cells attached to collagen enhanced tyrosine phosphorylation of FAK. Furthermore, ectopic expression of CD9 in fibrosarcoma cells affected adhesion-induced tyrosine phosphorylation of FAK, that correlated with the reorganization of the cortical actin cytoskeleton. These results show that tetraspanins can modulate integrin signaling, and point to a mechanism by which TM4SF proteins regulate cell motility.
authors.affiliation: CRC Institute for Cancer Studies, The University of Birmingham, Edgbaston, Birmingham, United Kingdom B15 2TA. f.beritchevski@bham.ac.uk
authors.forename: F
authors.initials: F
authors.lastname: Berditchevski
authors.forename: E
authors.initials: E
authors.lastname: Odintsova
mesh_terms: D000199:Actins / Q000378:metabolism; D015703:Antigens, CD / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D001943:Breast Neoplasms; D002448:Cell Adhesion / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000378:metabolism; D016895:Culture Media, Serum-Free; D003571:Cytochalasin B / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005354:Fibrosarcoma; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D039201:Integrin alpha3beta1; D016023:Integrins / Q000378:metabolism*; D007365:Intercellular Junctions / Q000187:drug effects / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000378:metabolism*; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D015739:Nocodazole / Q000494:pharmacology; D015388:Organelles / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D015398:Signal Transduction; D012995:Solubility; D016608:Talin / Q000378:metabolism; D060245:Tetraspanin 29; D014407:Tumor Cells, Cultured; D016596:Vinculin / Q000378:metabolism
chemical_list: D000199:Actins; D015703:Antigens, CD; C554869:CD9 protein, human; D015815:Cell Adhesion Molecules; D016895:Culture Media, Serum-Free; D016326:Extracellular Matrix Proteins; D039201:Integrin alpha3beta1; D016023:Integrins; D047908:Intracellular Signaling Peptides and Proteins; C000619710:MARCKS protein, human; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011506:Proteins; D016608:Talin; D060245:Tetraspanin 29; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D016596:Vinculin; D003571:Cytochalasin B; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D015739:Nocodazole