Effective activation of the proenzyme form of the urokinase-type plasminogen activator (pro-uPA) by the cysteine protease cathepsin L
Abstract
Increased levels of both the cysteine protease, cathepsin L, and the serine protease, uPA (urokinase-type plasminogen activator), are present in solid tumors and are correlated with malignancy. uPA is released by tumor cells as an inactive single-chain proenzyme (pro-uPA) which has to be activated by proteolytic cleavage. We analyzed in detail the action of the cysteine protease, cathepsin L, on recombinant human pro-uPA. Enzymatic assays, SDS-PAGE and Western blot analysis revealed that cathepsin L is a potent activator of pro-uPA. As determined by N-terminal amino acid sequence analysis, activation of pro-uPA by cathepsin L is achieved by cleavage or the Lys 158-lle 159 peptide bond, a common activation site of serine proteases such as plasmin and kallikrein. Similar to cathepsin B (Kobayashi et al., J. Biol. Chem. (1991) 266, 5147-5152) cleavage of pro-uPA by cathepsin L was most effective at acidic pH (molar ratio of cathepsin L to pro-uPA of 1:2,000). Nevertheless, even at pH 7.0, pro-uPA was activated by cathepsin L, although a 10-fold higher concentration of cathepsin L was required. As tumor cells may produce both pro-uPA and cathepsin L, implications for the activation of tumor cell-derived pro-uPA by cathepsin L may be considered. Different pathways activation of pro-uPA in tumor tissues may coexist: (i) autocatalytic intrinsic activation of pro-uPA; (ii) activation by serine proteases (plasmin, kallikrein. Factor XIIa); and (iii) activation by cysteine proteases (cathepsin B and L).
- Publication:
-
FEBS Letters
- Pub Date:
- January 1992
- DOI:
- 10.1016/0014-5793(92)80339-I
- Bibcode:
- 1992FEBSL.297..112G
- Keywords:
-
- Pro-uPA;
- Urokinase;
- Cysteine protease;
- Cathepsin B;
- Cathepsin L;
- N-Terminal amino acid sequence analysis;
- BSA;
- bovine serum albumin;
- GFD;
- growth factor-like domain;
- E-64;
- trans-epoxysuccinyl-L-leucylamino-(guanidino)-butane;
- HPLC;
- high-performance liquid chromatography;
- HMW-uPA;
- high molecular weight form of uPA;
- mab;
- monoclonal antibody;
- pro-uPA;
- proenzyme form of uPA (enzymatically inactive);
- uPA;
- urokinase-type plasminogen activator