Inhibition of pericellular plasminogen activation by apolipoprotein(a): Roles of urokinase plasminogen activator receptor and integrins αMβ2 and αVβ3. (August 2018)

• Record Type: Journal Article
• Authors: Romagnuolo, Rocco; Scipione, Corey A.; Bazzi, Zainab A.; Boffa, Michael B.; Koschinsky, Marlys L.
• Is Part Of: Atherosclerosis. Volume 275(2018)
• Page Start: 11
• Page End: 21
• Publication Date: 2018-08
• Subjects: Plasminogen activation -- Lipoprotein(a) -- uPAR -- Atherothrombosis -- Cardiovascular disease -- Receptors; Arteriosclerosis -- Periodicals; Electronic journals; 616.136
• DOI: 10.1016/j.atherosclerosis.2018.05.029
• Languages: English
• ISSNs: 0021-9150

Abstract

Abstract: Background and aims: Lipoprotein(a) (Lp(a)) is a causal risk factor for cardiovascular disorders including coronary heart disease and calcific aortic valve stenosis. Apolipoprotein(a) (apo(a)), the unique glycoprotein component of Lp(a), contains sequences homologous to plasminogen. Plasminogen activation is markedly accelerated in the presence of cell surface receptors and can be inhibited in this context by apo(a). Methods: We evaluated the role of potential receptors in regulating plasminogen activation and the ability of apo(a) to mediate inhibition of plasminogen activation on vascular and monocytic/macrophage cells through knockdown (siRNA or blocking antibodies) or overexpression of various candidate receptors. Binding assays were conducted to determine apo(a) and plasminogen receptor interactions. Results: The urokinase-type plasminogen activator receptor (uPAR) modulates plasminogen activation as well as plasminogen and apo(a) binding on human umbilical vein endothelial cells (HUVECs), human acute monocytic leukemia (THP-1) cells, and THP-1 macrophages as determined through uPAR knockdown and overexpression. Apo(a) variants lacking either the kringle V or the strong lysine binding site in kringle IV type 10 are not able to bind to uPAR to the same extent as wild-type apo(a). Plasminogen activation is also modulated, albeit to a lower extent, through the Mac-1 (αM β2 ) integrin on HUVECs and THP-1 monocytes. Integrin αV β3 can regulate plasminogen activation on THP-1 monocytes and to a lesser extent on HUVECs. Conclusions: These results indicate cell type-specific roles for uPAR, αM β2, and αV β3 in promoting plasminogen activation and mediate the inhibitory effects of apo(a) in this process. Highlights: Receptors uPAR, αM β2, and αV β3 all play roles in mediating plasminogen activation. Apo(a)'s inhibitory effects on plasminogen activation occur through these receptors. Identified domains in apo(a) are necessary for plasminogen activation inhibition. uPAR binds to apo(a) in vitro .