Apoptosis of human neutrophils induced by protein phosphatase 1/2A inhibition is caspase-independent and serine protease-dependent.
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.
Park
Hae-Young
HY
Department of Biochemistry, School of Medicine and Medical Research Center for Cancer Molecular Therapy, Dong-A University, Busan, Korea.
Song
Min-Gyu
MG
Lee
Jun-Sik
JS
Kim
Ja-Woong
JW
Jin
Jun-O
JO
Park
Joo-In
JI
Chang
Young-Chae
YC
Kwak
Jong-Young
JY
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D008387:Marine Toxins; D053146:Myeloblastin / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D019319:Okadaic Acid / Q000494:pharmacology*; D010080:Oxazoles / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051571:Protein Kinase C-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D054645:Protein Phosphatase 1; D012697:Serine Endopeptidases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013450:Sulfones / Q000494:pharmacology; D013997:Time Factors
D000590:Amino Acid Chloromethyl Ketones; D051033:Apoptosis Inducing Factor; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D047428:Protein Kinase Inhibitors; D015842:Serine Proteinase Inhibitors; D013450:Sulfones; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019319:Okadaic Acid; C002010:4-(2-aminoethyl)benzenesulfonylfluoride; C059041:calyculin A; D016572:Cyclosporine; D051571:Protein Kinase C-alpha; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D012697:Serine Endopeptidases; D053146:Myeloblastin; D053148:Caspase 3