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Apoptosis of human neutrophils induced by protein phosphatase 1/2A inhibition is caspase‐independent and serine protease‐dependent
Author(s) -
Park HaeYoung,
Song MinGyu,
Lee JunSik,
Kim JaWoong,
Jin JunO,
Park JooIn,
Chang YoungChae,
Kwak JongYoung
Publication year - 2007
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.21039
Subject(s) - apoptosis , annexin , serine protease , inhibitor of apoptosis domain , microbiology and biotechnology , caspase , phosphatase , dna fragmentation , protease , okadaic acid , chemistry , programmed cell death , biology , biochemistry , enzyme , phosphorylation
Protein phosphatase (PP) activity is associated with the regulation of apoptosis in neutrophils. However, the underlying regulatory mechanism(s) in apoptosis remain unclear. The type of cell death induced by okadaic acid (OA), the inhibitor of PP1 and PP2A, is characterized by apoptotic morphological changes of the cells and annexin V‐positive staining without DNA fragmentation. The apoptotic effects of OA and calyculin A on neutrophils were observed at concentrations ranging from 50 to 200 nM, or 10 to 50 nM, respectively. Cyclosporine A (a PP2B specific inhibitor), however, did not exhibit any pro‐apoptotic effects. OA and calyculin A, but not cyclosporine A, exhibited significant effects on protein levels and on the electrophoretic mobility of Mcl‐1. zVAD‐fmk, a pancaspase inhibitor, failed to inhibit the effect of OA on the caspase‐3 activity, procaspase‐3 processing, and the apoptotic rate of neutrophils. However, 4‐(2‐aminoethyl) benzenesulfonylfluoride (AEBSF), a general serine protease inhibitor, significantly abrogated the OA‐induced mobility shift in procaspase‐3, caspase‐3 activation, and the apoptotic morphological changes in neutrophils. Moreover, OA enhanced the serine protease activity of the neutrophils. The addition of the proteinase‐3 protein increased the rate of neutrophil apoptosis, which was also blocked by AEBSF but not by zVAD‐fmk. These results suggest that OA induces procaspase‐3 processing but that OA‐induced apoptosis is caspase‐independent and serine protease‐dependent. J. Cell. Physiol. 212: 450–462, 2007. © 2007 Wiley‐Liss, Inc.