Tyrosine phosphorylation of human urokinase-type plasminogen activator.
Immunoblotting analysis of purified human urokinase plasminogen activator (u-PA), gives a positive signal when reacted with anti-phosphotyrosine monoclonal antibodies (MoAb anti-P-Tyr); competition with o-phospho-DL-tyrosine (P-Tyr) but not o-phospho-DL-threonine or serine (P-Treo, P-Ser) completely suppresses this signal. Either the 55 kDa u-PA form and the lower Mw form (33 kDa) derived from the 55 kDa u-PA are Tyr-phosphorylated also the u-PA secreted in the culture media of human fibrosarcoma cells (HT-1080) is phosphorylated in tyrosine as well as u-PA present in tissue extracts of tumors induced in nude mice by HT-1080 cells. These data show that urine purified human u-PA and u-PA produced by human fibrosarcoma cells, in vitro and in vivo, are phosphorylated in tyrosine; furthermore our data show that u-PA is the major Tyr-phosphorylated protein present in these human tumor cells.
Barlati
S
S
Department of Biomedical Sciences and Biotechnologies, University of Brescia, Italy.
Paracini
F
F
Bellotti
D
D
De Petro
G
G
D000818:Animals; D002460:Cell Line; D004792:Enzyme Precursors / Q000302:isolation & purification / Q000378:metabolism*; D005354:Fibrosarcoma / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D010766:Phosphorylation; D010960:Plasminogen Activators / Q000302:isolation & purification / Q000378:metabolism*; D014183:Transplantation, Heterologous; D014443:Tyrosine; D014568:Urokinase-Type Plasminogen Activator / Q000302:isolation & purification / Q000378:metabolism*
D004792:Enzyme Precursors; D007527:Isoenzymes; D014443:Tyrosine; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator