Inhibitors of protein phosphatases 1 and 2A differentially prevent intrinsic and extrinsic apoptosis pathways

• Published in: Biochemical and biophysical research communications Vol. 323; no. 4; pp. 1313 - 1320
• Main Authors: Chatfield, Kathryn, Eastman, Alan
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 29-10-2004
• Subjects: Anisomycin; Apoptosis; Apoptosis - drug effects; Burkitt Lymphoma - metabolism; Burkitt Lymphoma - pathology; Calyculin A; Cell Line, Tumor; Enzyme Inhibitors - pharmacology; Fas; Humans; Jurkat Cells; Okadaic acid; Okadaic Acid - pharmacology; Oxazoles - pharmacology; Phosphoprotein Phosphatases - antagonists & inhibitors; Phosphoprotein Phosphatases - classification; Phosphoprotein Phosphatases - metabolism; Pyrans - pharmacology; Signal Transduction - drug effects; Spiro Compounds - pharmacology; Tautomycin; U937 Cells; Fas; Okadaic acid; Anisomycin; Calyculin A; Tautomycin; Apoptosis
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2004.09.003

Inhibitors of serine/threonine protein phosphatases can inhibit apoptosis. We investigated which protein phosphatases are critical for this protection using calyculin A, okadaic acid, and tautomycin. All three phosphatase inhibitors prevented anisomycin-induced apoptosis in leukemia cell models. In vitro, calyculin A does not discriminate between PP1 and PP2A, while okadaic acid and tautomycin are more selective for PP2A and PP1, respectively. Increased phosphorylation of endogenous marker proteins was used to define concentrations that inhibited each phosphatase in cells. Concentrations of each inhibitor that prevented anisomycin-induced apoptosis correlated with inhibition of PP2A. The inhibitors prevented Bax translocation to mitochondria, indicating inhibition upstream of mitochondria. Tautomycin and calyculin A, but not okadaic acid, also prevented apoptosis induced through the CD95/Fas death receptor, and this protection correlated with inhibition of PP1. The inhibitors prevented Fas receptor oligomerization, FADD recruitment, and caspase 8 activation. The differential effects of PP1 and PP2A in protection from death receptor and mitochondrial-mediated pathways of death, respectively, may help one to define critical steps in each pathway, and regulatory roles for serine/threonine phosphatases in apoptosis.