The Mr 17500 region of the A chain of urokinase is required for interaction with a specific receptor in A431 cells.
We have found the existence of specific receptors for the plasminogen activator, urokinase, in A431 human epidermoid carcinoma cells, cultures in plasminogen-free conditions. Two subsets of receptors have been recognized on the basis of 125I-labelled urokinase binding analysis: about 1 X 10(3) high-affinity (Kd = 5.0 X 10(-11) M) and 1 X 10(5) low-affinity (Kd = 9 X 10(-9) M) receptors per cell. The electron microscopic observation of a urokinase: ferritin conjugate has shown single and clustered receptors at the cell surface. Down-regulation of the receptors (T1/2 = 3.77 h) follows the binding of urokinase. The binding does not involve an intact catalytic site and is inhibited by a monoclonal antibody against the Mr 17500 proteolytic fragment of the A chain of urokinase.
D016564:Amyloid beta-Protein Precursor; D000911:Antibodies, Monoclonal; D001550:Benzamidines / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell; D002352:Carrier Proteins / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D008854:Microscopy, Electron; D008970:Molecular Weight; D058255:Protease Nexins; D011956:Receptors, Cell Surface / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator / Q000276:immunology / Q000378:metabolism*
D016564:Amyloid beta-Protein Precursor; D000911:Antibodies, Monoclonal; D001550:Benzamidines; D002352:Carrier Proteins; C524898:PLAUR protein, human; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; C006500:4-aminobenzamidine; D014568:Urokinase-Type Plasminogen Activator