Suppression of ADAM17-mediated Lyn/Akt pathways induces apoptosis of human leukemia U937 cells: Bungarus multicinctus protease inhibitor-like protein-1 uncovers the cytotoxic mechanism.
Cell surface proteases have been demonstrated to play an important role in facilitating cell invasion into the extracellular matrix and may contribute significantly to extracellular matrix degradation by metastatic cancer cells. Abundant expression of these enzymes is associated with poor prognosis. Thus, protease inhibitors that repress cell surface proteases may be applicable to cancer therapy. Because soybean Kunitz-type trypsin inhibitor has been found to induce apoptotic death of human leukemia Jurkat cells, anti-leukemia activity of Bungarus multicinctus protease inhibitor-like protein-1 (PILP-1) is thus examined. PILP-1 induced apoptosis of human leukemia U937 cells, characteristic of loss of mitochondrial membrane potential, degradation of procaspase-8, and production of t-Bid. FADD down-regulation neither restored viability of PILP-1-treated cells nor attenuated production of active caspase-8 and t-Bid in PILP-1-treated cells, suggesting that the death receptor-mediated pathway was not involved in the cytotoxicity of PILP-1. It was found that PILP-1-evoked p38 MAPK activation and ERK inactivation led to PILP-1-induced cell death and down-regulation of ADAM17. Knockdown of ADAM17 by siRNA induced death of U937 cells and inactivation of Lyn and Akt. Immunoprecipitation suggested that ADAM17 and Lyn form complexes. Overexpression of ADAM17, LynY507F (gain of function), and constitutively active Akt suppressed the cytotoxic effects of PILP-1. PILP-1-elicited inactivation of Lyn and Akt was abrogated in cells with overexpressed ADAM17 or LynY507F. Taken together, our data indicate that ADAM17-mediated activation of Lyn/Akt maintains the viability of U937 cells and that suppression of the pathway is responsible for PILP-1-induced apoptosis.
Liu
Wen-Hsin
WH
From the Institute of Biomedical Sciences, National Sun Yat-Sen University-Kaohsiung Medical University Joint Research Center, National Sun Yat-Sen University, Kaohsiung 804, Taiwan.
Chang
Long-Sen
LS
D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism*; D000072198:ADAM17 Protein; D019943:Amino Acid Substitution; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D002038:Bungarotoxins / Q000494:pharmacology*; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D053200:Fas-Associated Death Domain Protein / Q000235:genetics / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D020298:U937 Cells; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism*
D002038:Bungarotoxins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D009097:Multienzyme Complexes; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; D053181:Caspase 8; D051722:ADAM Proteins; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human