title: Annexin II-mediated plasmin generation activates TGF-beta3 during epithelial-mesenchymal transformation in the developing avian heart.
abstract: Epithelial-mesenchymal transformation (EMT), the process by which epithelial cells are converted into motile, invasive mesenchymal cells, is critical to valvulogenesis. Transforming growth factor-beta3 (TGF-beta3), an established mediator of avian atrioventricular (AV) canal EMT, is secreted as a latent complex. In vitro, plasmin-mediated proteolysis has been shown to release active TGF-betas from the latent complex. Annexin II, a co-receptor for tissue plasminogen activator (tPA) and plasminogen, promotes cell-surface generation of the serine protease plasmin. Here, we show that annexin II-mediated plasmin activity regulates release of active TGF-beta3 during chick AV canal EMT. Primary embryonic endocardial-derived cells express annexin II which promotes plasminogen activation in vitro. Incubation of heart explant cultures with either alpha(2)antiplasmin (alpha(2)AP), a major physiological plasmin inhibitor, or anti-annexin II IgG, blocked EMT by approximately 80%, and 50%, respectively. Anti-annexin II IgG-mediated inhibition of EMT was overcome by the addition of recombinant TGF-beta3. Upon treatment with anti-annexin II IgG or alpha(2)AP, conditioned medium from heart explant cultures showed absence of the active fragment of TGF-beta3 by Western blot analysis and a approximately 50% decrease in TGF-beta specific bioactivity. Our results suggest that annexin II-mediated plasmin activity regulates the release of active TGF-beta during cardiac valve development in the avian heart.
authors.affiliation: Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, NY 10021, USA.
authors.forename: Suba
authors.initials: S
authors.lastname: Krishnan
authors.forename: Arunkumar B
authors.initials: AB
authors.lastname: Deora
authors.forename: Justin P
authors.initials: JP
authors.lastname: Annes
authors.forename: Jerelyn
authors.initials: J
authors.lastname: Osoria
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Rifkin
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Hajjar
mesh_terms: D000818:Animals; D017306:Annexin A2 / Q000378:metabolism*; D001681:Biological Assay; D015152:Blotting, Northern; D015153:Blotting, Western; D002642:Chick Embryo; D004848:Epithelium / Q000196:embryology / Q000502:physiology; D005341:Fibrinolysin / Q000096:biosynthesis*; D006351:Heart Valves / Q000196:embryology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008648:Mesoderm / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D053782:Transforming Growth Factor beta3; D000979:alpha-2-Antiplasmin / Q000378:metabolism
chemical_list: D017306:Annexin A2; D016212:Transforming Growth Factor beta; D053782:Transforming Growth Factor beta3; D000979:alpha-2-Antiplasmin; D005341:Fibrinolysin