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Phorbol Ester Activation of a Proteolytic Cascade Capable of Activating Latent Transforming Growth Factor-β

Phorbol Ester Activation of a Proteolytic Cascade Capable of Activating Latent Transforming Growth Factor-β

Authors :
Bruce E. Linebaugh
Meng Guo
John J. Reiners
Patricia A. Mathieu
Bonnie F. Sloane
Source :
Journal of Biological Chemistry. 277:14829-14837
Publication Year :
2002
Publisher :
Elsevier BV, 2002.

Abstract

12-O-Tetradecanoylphorbol-13-acetate (TPA) suppresses the proliferation of the human breast epithelial cell line MCF10A-Neo by initiating proteolytic processes that activate latent transforming growth factor (TGF)-β in the serum used to supplement culture medium. Within 1 h of treatment, cultures accumulated an extracellular activity capable of cleaving a substrate for urokinase-type plasminogen activator (uPA) and tissue plasminogen activator (tPA). This activity was inhibited by plasminogen activator inhibitor-1 or antibodies to uPA but not tPA. Pro-uPA activation was preceded by dramatic changes in lysosome trafficking and the extracellular appearance of cathepsin B and β-hexosaminidase but not cathepsins D or L. Co-treatment of cultures with the cathepsin B inhibitors CA-074 or Z-FA-FMK suppressed the cytostatic effects of TPA and activation of pro-uPA. In the absence of TPA, exogenously added cathepsin B activated pro-uPA and suppressed MCF10A-Neo proliferation. The cytostatic effects of both TPA and cathepsin B were suppressed in cells cultured in medium depleted of plasminogen/plasmin or supplemented with neutralizing TGF-β antibody. Pretreatment with cycloheximide did not suppress the exocytosis of cathepsin B or the activation of pro-uPA. Hence, TPA activates signaling processes that trigger the exocytosis of a subpopulation of lysosomes/endosomes containing cathepsin B. Subsequently, extracellular cathepsin B initiates a proteolytic cascade involving uPA, plasminogen, and plasmin that activates serum-derived latent TGF-β.

Details

ISSN :
00219258
Volume :
277
Database :
OpenAIRE
Journal :
Journal of Biological Chemistry
Accession number :
edsair.doi...........03a8fd463dbad133e8a621c416cf05de
Full Text :
https://doi.org/10.1074/jbc.m108180200