Furin-like proprotein convertases are central regulators of the membrane type matrix metalloproteinase-pro-matrix metalloproteinase-2 proteolytic cascade in atherosclerosis.
BACKGROUND
Accumulation of macrophages and their in situ expression of matrix metalloproteinases (MMPs) are important determinants of plaque stability. Activation of membrane-bound MT1-MMP, the major activator of pro-MMP-2, requires intracellular endoproteolytic cleavage of its precursor protein. This type of activation typically requires suitable furin-like proprotein convertases (PCs), specifically furin and PC5. The present study was done to investigate the function of MT1-MMP as well as furin-like PCs in mononuclear inflammatory cells.


RESULTS
Macrophage differentiation of human monocytic THP-1 cells was accompanied by increased expression of furin, PC5, and MT1-MMP. Some pro-MMP-2 activation was found in macrophages, but pro-MMP-2 level or activation was not enhanced after stimulation with the proinflammatory mediators tumor necrosis factor-alpha or lipopolysaccharide. However, culturing of macrophages in conditioned medium from serum-starved vascular smooth muscle cells, which constitutively secrete pro-MMP-2, resulted in a strong pro-MMP-2 activation. Inhibition of furin-like PCs with the specific pharmacological inhibitor decanoyl-RVKR-chloromethylketone (dec-CMK) inhibited MT1-MMP activation in macrophages. Dec-CMK or furin-specific small interfering RNA significantly inhibited macrophage MT1-MMP-dependent activation of vascular smooth muscle cell-derived pro-MMP-2. Flow cytometry demonstrated that human circulating monocytes express furin and PC5, and MT1-MMP and immunohistochemistry revealed their colocalization in macrophages in advanced human atherosclerotic lesions.


CONCLUSIONS
Furin-like PCs (furin and PC5) play a central role in a MT-MMP-MMP-2 proteolytic cascade, involving provision of macrophage MT1-MMP for the activation of pro-MMP-2 synthesized by other cells. Furin and PC5 are expressed in human peripheral blood mononuclear cells and colocalize with MT1-MMP in macrophages in the atherosclerotic plaque, supporting the hypothesis that they are potential targets in atherosclerosis.
Stawowy
Philipp
P
Department of Medicine/Cardiology, Deutsches Herzzentrum Berlin, Augustenburger Platz 1, D-13353 Berlin, Germany. stawowy@dhzb.de
Meyborg
Heike
H
Stibenz
Dietger
D
Borges Pereira Stawowy
Núbia
N
Roser
Mattias
M
Thanabalasingam
Usan
U
Veinot
John P
JP
Chrétien
Michel
M
Seidah
Nabil G
NG
Fleck
Eckart
E
Graf
Kristof
K
D001161:Arteriosclerosis / Q000201:enzymology* / Q000209:etiology; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D045683:Furin / Q000032:analysis / Q000502:physiology; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000201:enzymology; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D020782:Matrix Metalloproteinases / Q000378:metabolism; D053504:Matrix Metalloproteinases, Membrane-Associated; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism; D045702:Proprotein Convertase 5 / Q000032:analysis / Q000502:physiology; D043484:Proprotein Convertases / Q000032:analysis / Q000502:physiology*; D011498:Protein Precursors / Q000378:metabolism
D017077:Culture Media, Conditioned; D011498:Protein Precursors; D045702:Proprotein Convertase 5; D043484:Proprotein Convertases; D045683:Furin; D020782:Matrix Metalloproteinases; D053504:Matrix Metalloproteinases, Membrane-Associated; D020778:Matrix Metalloproteinase 2