title: Formation of a beta1 integrin signaling complex in Schwann cells is independent of rho.
abstract: Schwann cell adhesion to basal lamina is essential for peripheral nerve development. beta(1) integrin receptors for extracellular matrix cooperate with other receptors to transmit signals that coordinate cell cycle progression and initiation of differentiation, including myelin-specific gene expression. In Schwann cell/sensory neuron cocultures, beta(1) integrins complex with focal adhesion kinase (FAK), fyn kinase, paxillin, and schwannomin in response to basal lamina adhesion. To study the assembly of this signaling complex in Schwann cells (SCs), we induced beta(1) integrin clustering on suspended cells using an immobilized antibody and recovered a complex containing beta(1) integrin, FAK, paxillin, and schwannomin. In adherent subconfluent cells, the proteins colocalized to filopodia, ruffling membranes and focal contacts. We assessed the role of rhoGTPase in the process of integrin complex assembly by introducing C3 transferase (C3T), a rho inhibitor, into the cells. Although C3T caused dose-dependent morphological abnormalities, FAK, paxillin, and schwannomin were able to coimmunoprecipitate with beta(1) integrin. Additionally, colocalization of FAK, paxillin, and schwannomin with beta(1) integrin in filopodia and small focal contacts remained unchanged. We conclude that SCs do not require active rho to recruit signaling and structural proteins to beta(1) integrins clustered at the plasma membrane. Rho is required to establish large focal adhesions and to spread and stabilize plasma membrane extensions.
authors.affiliation: Department of Molecular Biology and Microbiology, University of Central Florida, Orlando 32826, USA.
authors.forename: Anna R
authors.initials: AR
authors.lastname: Taylor
authors.forename: Sandra E
authors.initials: SE
authors.lastname: Geden
authors.forename: Cristina
authors.initials: C
authors.lastname: Fernandez-Valle
mesh_terms: D036002:ADP Ribose Transferases / Q000494:pharmacology; D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology; D002021:Buffers; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D007150:Immunohistochemistry; D007163:Immunosorbent Techniques; D019012:Integrin beta1 / Q000737:chemistry / Q000378:metabolism*; D046911:Macromolecular Substances; D025581:Neurofibromin 2 / Q000378:metabolism; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism; D020743:rhoB GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D002021:Buffers; D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D019012:Integrin beta1; D046911:Macromolecular Substances; D025581:Neurofibromin 2; D051419:Paxillin; D010750:Phosphoproteins; C496063:Pxn protein, rat; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496052:Ptk2 protein, rat; D001905:Botulinum Toxins; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein