Epidermal growth factor‐binding protein activates soluble and receptor‐bound single chain urokinase‐type plasminogen activator

[摘要]

Epidermal growth factor-binding protein (EGF-BP) is a serine proteinase that reversibly associates with epidermal growth factor (EGF). We analyzed the reaction of EGF-BP with urokinase type plasminogen activator (u-PA), a serine proteinase that promotes pericellular proteolysis and cellular migration. EGF-BP cleaved single chain u-PA (scu-PA) between Lys¹⁵⁸ and Ile¹⁵⁹, converting the zymogen into enzymatically active two-chain u-PA (tcu-PA), as shown by SDS-PAGE, N-terminal sequence analysis, and enzymatic assay. The k _cat and K _m of the activation reaction were (5.6 ± 0.6) × 10⁻² s ⁻¹ and 2,0 ± 0.3 μM, yielding a catalytic efficiency of 2.8 × 10⁴ M⁻¹. EGF-BP also activated scu-PA bound to receptors on U937 monocytes as demonstrated by the generation of amidase activity against a tcu-PA-specific fluorogenic substrate. By activating scu-PA, EGF-BP may initiate u-PA-dependent cell surface proteolysis and therefore enhance EGF activities that require cellular migration and/or tissue remodeling.

[学科分类] 生物化学/生物物理

[关键词] Urokinase-type plasminogen activator;Urokinase-type plasminogen activator receptor;Epidermal growth factor binding protein;Epidermal growth factor;EGF;epidermal growth factor;EGF-BP;EGF-binding protein;NGF-γ;nerve growth factor-γ;scu-PA;single chain urokinase type plasminogen activator;tcu-PA;two chain urokinase type plasminogen activator;uPAR;urokinase type plasminogen activator receptor;PPACK;d-phenylalanyl-l-prolyl-arginine chloromethyl ketone;S-2444;hydrochloride;S-2251;dihydrochloride;PMA;phorbol 12-myristate 13-acetate;PNPGB;p-nitrophenyl p′-guanidinobenzoate hydrochloride;EGR-AMC;glutamyl-glycyl-arginine-7-amino-4-methyl coumarin;S.E.M.;standard error of the mean