TY - JOUR
T1 - Cell Surface-Dependent Generation of Angiostatin4.5
AU - Wang, Hao
AU - Schultz, Ryan
AU - Hong, Jerome
AU - Cundiff, Deborah L.
AU - Jiang, Keyi
AU - Soff, Gerald A.
PY - 2004/1/1
Y1 - 2004/1/1
N2 - Angiostatin4.5 (AS4.5) is a naturally occurring human angiostatin isoform, consisting of plasminogen kringles 1-4 plus 85% of kringle 5 (amino acids Lys78 to Arg529). Prior studies indicate that plasminogen is converted to AS4.5 in a two-step reaction. First, plasminogen is activated to plasmin. Then plasmin undergoes autoproteolysis within the inner loop of kringle 5, which can be induced by a free sulfhydryl donor or an alkaline pH. We now demonstrate that plasminogen can be converted to AS4.5 in a cell membrane-dependent reaction. Actin was shown previously to be a surface receptor for plasmin(ogen). We now show that β-actin is present on the extracellular membranes of cancer cells (PC-3, HT1080, and MDA-MB231), and β-actin can mediate plasmin binding to the cell surface and autoproteolysis to AS4.5. In the presence of β-actin, no small molecule-free sulfhydryl donor is needed for generation of AS4.5. Antibodies to actin reduced membrane-dependent generation of AS4.5 by 70%. In a cell-free system, addition of actin to in vitro-generated plasmin resulted in stoichiometric conversion to AS4.5. Annexin II and α-enolase have been reported to be plasminogen receptors, but we did not demonstrate a role for these proteins in conversion of plasminogen to AS4.5. Our data indicate that membrane-associated β-actin, documented previously as a plasminogen receptor, is a key cell membrane receptor capable of mediating conversion of plasmin to AS4.5. This conversion may serve an important role in regulating tumor angiogenesis, invasion, and metastasis, and surface β-actin may also serve as a prognostic marker to predict tumor behavior.
AB - Angiostatin4.5 (AS4.5) is a naturally occurring human angiostatin isoform, consisting of plasminogen kringles 1-4 plus 85% of kringle 5 (amino acids Lys78 to Arg529). Prior studies indicate that plasminogen is converted to AS4.5 in a two-step reaction. First, plasminogen is activated to plasmin. Then plasmin undergoes autoproteolysis within the inner loop of kringle 5, which can be induced by a free sulfhydryl donor or an alkaline pH. We now demonstrate that plasminogen can be converted to AS4.5 in a cell membrane-dependent reaction. Actin was shown previously to be a surface receptor for plasmin(ogen). We now show that β-actin is present on the extracellular membranes of cancer cells (PC-3, HT1080, and MDA-MB231), and β-actin can mediate plasmin binding to the cell surface and autoproteolysis to AS4.5. In the presence of β-actin, no small molecule-free sulfhydryl donor is needed for generation of AS4.5. Antibodies to actin reduced membrane-dependent generation of AS4.5 by 70%. In a cell-free system, addition of actin to in vitro-generated plasmin resulted in stoichiometric conversion to AS4.5. Annexin II and α-enolase have been reported to be plasminogen receptors, but we did not demonstrate a role for these proteins in conversion of plasminogen to AS4.5. Our data indicate that membrane-associated β-actin, documented previously as a plasminogen receptor, is a key cell membrane receptor capable of mediating conversion of plasmin to AS4.5. This conversion may serve an important role in regulating tumor angiogenesis, invasion, and metastasis, and surface β-actin may also serve as a prognostic marker to predict tumor behavior.
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U2 - 10.1158/0008-5472.CAN-03-1862
DO - 10.1158/0008-5472.CAN-03-1862
M3 - Article
C2 - 14729620
AN - SCOPUS:1642494842
SN - 0008-5472
VL - 64
SP - 162
EP - 168
JO - Cancer Research
JF - Cancer Research
IS - 1
ER -