Angiostatin inhibits endothelial and melanoma cellular invasion by blocking matrix-enhanced plasminogen activation.
Angiostatin, a kringle-containing fragment of plasminogen, is a potent inhibitor of angiogenesis. The mechanism(s) responsible for the anti-angiogenic properties of angiostatin are unknown. We now report that human angiostatin blocks plasmin(ogen)-enhanced in vitro invasion of tissue plasminogen activator (t-PA)-producing endothelial and melanoma cells. Kinetic analyses demonstrated that angiostatin functions as a non-competitive inhibitor of extracellular-matrix (ECM)-enhanced, t-PA-catalysed plasminogen activation, with a Ki of 0.9+/-0.03 microM. This mechanism suggests that t-PA has a binding site for the inhibitor angiostatin, as well as for its substrate plasminogen that, when occupied, prevents ternary complex formation between t-PA, plasminogen and matrix protein. Direct binding experiments confirmed that angiostatin bound to t-PA with an apparent Kd [Kd(app)] of 6.7+/-0.7 nM, but did not bind with high affinity to ECM proteins. Together, these data suggest that angiostatin in the cellular micro-environment can inhibit matrix-enhanced plasminogen activation, resulting in reduced invasive activity, and suggest a biochemical mechanism whereby angiostatin-mediated regulation of plasmin formation could influence cellular migration and invasion.
Stack
M S
MS
Department of Obstetrics and Gynecology, Northwestern University Medical School, Chicago, IL 60611, USA. mss130@anima.nums.nwu.edu
Gately
S
S
Bafetti
L M
LM
Enghild
J J
JJ
Soff
G A
GA
D043168:Angiostatins; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002417:Cattle; D002465:Cell Movement / Q000187:drug effects*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005109:Extracellular Matrix / Q000502:physiology*; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005260:Female; D005341:Fibrinolysin / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008545:Melanoma / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D009389:Neovascularization, Pathologic; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D010958:Plasminogen / Q000378:metabolism* / Q000494:pharmacology*; D011485:Protein Binding; D010959:Tissue Plasminogen Activator / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D000979:alpha-2-Antiplasmin / Q000378:metabolism / Q000494:pharmacology
D000906:Antibodies; D016326:Extracellular Matrix Proteins; D010446:Peptide Fragments; D000979:alpha-2-Antiplasmin; D043168:Angiostatins; D010958:Plasminogen; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin