title: Human plasminogen kringle 1-5 inhibits angiogenesis and induces thrombomodulin degradation in a protein kinase A-dependent manner.
abstract: Kringle 1-5 (K1-5), an endogenous proteolytic fragment of human plasminogen (Plg), is an angiostatin-related protein that inhibits angiogenesis. Many angiostatin-related proteins have been identified, but the detailed molecular mechanisms underlying their antiangiogenic effects remain unclear. Thrombomodulin (TM) is a transmembrane glycoprotein that plays a major role in the anticoagulation process in endothelial cells. Previously, we demonstrated that recombinant TM could interact with Plg to enhance Plg activation. In the present study, we investigated the interaction between TM and K1-5, and their functions in endothelial cells. We found that K1-5 colocalized with TM and directly interacted with TM through the TM lectin-like domain. After K1-5 interacted with TM, it induced TM internalization and degradation. In addition, the K1-5-induced TM internalization and degradation in proteasomes after ubiquitin modification were dependent on protein kinase A (PKA). Moreover, a PKA-specific inhibitor reversed the effects of K1-5 on cell migration and tube formation. Consistent with these findings, TM overexpression resulted in increased cell migration; moreover, K1-5 inhibited the increase of TM-mediated cell migration in a PKA-dependent manner. We determined that TM acts as a K1-5 receptor and that K1-5 induces TM internalization, ubiquitination, and degradation through the PKA pathway, by which K1-5 may inhibit endothelial cell migration and tube formation.
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan; Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Chia-Fong
authors.initials: CF
authors.lastname: Cho
authors.forename: Po-Ku
authors.initials: PK
authors.lastname: Chen
authors.forename: Po-Chiao
authors.initials: PC
authors.lastname: Chang
authors.forename: Hau-Lin
authors.initials: HL
authors.lastname: Wu
authors.forename: Guey-Yueh
authors.initials: GY
authors.lastname: Shi
mesh_terms: D000818:Animals; D002417:Cattle; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism; D006801:Humans; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D010958:Plasminogen / Q000737:chemistry / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055550:Protein Stability / Q000187:drug effects; D021381:Protein Transport; D059748:Proteolysis / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D018180:Thrombomodulin / Q000737:chemistry / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects
chemical_list: D010446:Peptide Fragments; D018180:Thrombomodulin; D010958:Plasminogen; D017868:Cyclic AMP-Dependent Protein Kinases; D046988:Proteasome Endopeptidase Complex
keywords: Angiogenesis; Kringle 1–5; Protein kinase A; Thrombomodulin