title: Regulation of tenascin-C, a vascular smooth muscle cell survival factor that interacts with the alpha v beta 3 integrin to promote epidermal growth factor receptor phosphorylation and growth.
abstract: Tenascin-C (TN-C) is induced in pulmonary vascular disease, where it colocalizes with proliferating smooth muscle cells (SMCs) and epidermal growth factor (EGF). Furthermore, cultured SMCs require TN-C for EGF-dependent growth on type I collagen. In this study, we explore the regulation and function of TN-C in SMCs. We show that a matrix metalloproteinase (MMP) inhibitor (GM6001) suppresses SMC TN-C expression on native collagen, whereas denatured collagen promotes TN-C expression in a beta 3 integrin- dependent manner, independent of MMPs. Floating type I collagen gel also suppresses SMC MMP activity and TN-C protein synthesis and induces apoptosis, in the presence of EGF. Addition of exogenous TN-C to SMCs on floating collagen, or to SMCs treated with GM6001, restores the EGF growth response and "rescues" cells from apoptosis. The mechanism by which TN-C facilitates EGF-dependent survival and growth was then investigated. We show that TN-C interactions with alpha v beta 3 integrins modify SMC shape, and EGF- dependent growth. These features are associated with redistribution of filamentous actin to focal adhesion complexes, which colocalize with clusters of EGF-Rs, tyrosine-phosphorylated proteins, and increased activation of EGF-Rs after addition of EGF. Cross-linking SMC beta 3 integrins replicates the effect of TN-C on EGF-R clustering and tyrosine phosphorylation. Together, these studies represent a functional paradigm for ECM-dependent cell survival whereby MMPs upregulate TN-C by generating beta 3 integrin ligands in type I collagen. In turn, alpha v beta 3 interactions with TN-C alter SMC shape and increase EGF-R clustering and EGF-dependent growth. Conversely, suppression of MMPs downregulates TN-C and induces apoptosis.
authors.affiliation: Division of Cardiovascular Research, Research Institute, The Hospital for Sick Children, University of Toronto, Ontario, Canada.
authors.forename: P L
authors.initials: PL
authors.lastname: Jones
authors.forename: J
authors.initials: J
authors.lastname: Crack
authors.forename: M
authors.initials: M
authors.lastname: Rabinovitch
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D004815:Epidermal Growth Factor / Q000502:physiology; D066246:ErbB Receptors / Q000187:drug effects / Q000378:metabolism*; D008024:Ligands; D008297:Male; D008666:Metalloendopeptidases / Q000096:biosynthesis; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D011651:Pulmonary Artery; D051381:Rats; D017207:Rats, Sprague-Dawley; D011940:Receptor Aggregation / Q000187:drug effects; D019030:Receptors, Vitronectin / Q000378:metabolism / Q000502:physiology*; D019063:Tenascin / Q000096:biosynthesis / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D000199:Actins; D008024:Ligands; D019030:Receptors, Vitronectin; D019063:Tenascin; D014443:Tyrosine; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D008666:Metalloendopeptidases