Inhibition of protein phosphatase 2A (PP2A) prevents Mcl-1 protein dephosphorylation at the Thr-163/Ser-159 phosphodegron, dramatically reducing expression in Mcl-1-amplified lymphoma cells

Shanna K Nifoussi; Nora R Ratcliffe; Deborah L Ornstein; Gary Kasof; Stefan Strack; Ruth W Craig

doi:10.1074/jbc.M114.587873

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Inhibition of protein phosphatase 2A (PP2A) prevents Mcl-1 protein dephosphorylation at the Thr-163/Ser-159 phosphodegron, dramatically reducing expression in Mcl-1-amplified lymphoma cells

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Inhibition of protein phosphatase 2A (PP2A) prevents Mcl-1 protein dephosphorylation at the Thr-163/Ser-159 phosphodegron, dramatically reducing expression in Mcl-1-amplified lymphoma cells

Shanna K Nifoussi, Nora R Ratcliffe, Deborah L Ornstein, Gary Kasof, Stefan Strack and Ruth W Craig

The Journal of biological chemistry, Vol.289(32), pp.21950-21959

08/08/2014

DOI: 10.1074/jbc.M114.587873

PMCID: PMC4139212

PMID: 24939844

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Abstract

Abundant, sustained expression of prosurvival Mcl-1 is an important determinant of viability and drug resistance in cancer cells. The Mcl-1 protein contains PEST sequences (enriched in proline, glutamic acid, serine, and threonine) and is normally subject to rapid turnover via multiple different pathways. One of these pathways involves a phosphodegron in the PEST region, where Thr-163 phosphorylation primes for Ser-159 phosphorylation by glycogen synthase kinase-3. Turnover via this phosphodegron-targeted pathway is reduced in Mcl-1-overexpressing BL41-3 Burkitt lymphoma and other cancer cells; turnover is further slowed in the presence of phorbol ester-induced ERK activation, resulting in Mcl-1 stabilization and an exacerbation of chemoresistance. The present studies focused on Mcl-1 dephosphorylation, which was also found to profoundly influence turnover. Exposure of BL41-3 cells to an inhibitor of protein phosphatase 2A (PP2A), okadaic acid, resulted in a rapid increase in phosphorylation at Thr-163 and Ser-159, along with a precipitous decrease in Mcl-1 expression. The decline in Mcl-1 expression preceded the appearance of cell death markers and was not slowed in the presence of phorbol ester. Upon exposure to calyculin A, which also potently inhibits PP2A, versus tautomycin, which does not, only the former increased Thr-163/Ser-159 phosphorylation and decreased Mcl-1 expression. Mcl-1 co-immunoprecipitated with PP2A upon transfection into CHO cells, and PP2A/Aα knockdown recapitulated the increase in Mcl-1 phosphorylation and decrease in expression. In sum, inhibition of PP2A prevents Mcl-1 dephosphorylation and results in rapid loss of this prosurvival protein in chemoresistant cancer cells.

Okadaic Acid - pharmacology

Gene Expression

Threonine - chemistry

Tetradecanoylphorbol Acetate - pharmacology

Protein Phosphatase 2 - antagonists & inhibitors

Humans

Enzyme Inhibitors - pharmacology

Myeloid Cell Leukemia Sequence 1 Protein - metabolism

Protein Phosphatase 2 - genetics

Burkitt Lymphoma - metabolism

Drug Resistance, Neoplasm

Serine - chemistry

Myeloid Cell Leukemia Sequence 1 Protein - genetics

Gene Knockdown Techniques

MAP Kinase Signaling System

Marine Toxins

Proteolysis

Burkitt Lymphoma - genetics

Cell Line, Tumor

Myeloid Cell Leukemia Sequence 1 Protein - chemistry

Oxazoles - pharmacology

Phosphorylation - drug effects

Binding Sites

Burkitt Lymphoma - drug therapy

Details

Title: Subtitle: Inhibition of protein phosphatase 2A (PP2A) prevents Mcl-1 protein dephosphorylation at the Thr-163/Ser-159 phosphodegron, dramatically reducing expression in Mcl-1-amplified lymphoma cells
Creators: Shanna K Nifoussi - From the Departments of Pharmacology and Toxicology and the Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766
Nora R Ratcliffe - Pathology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, the Veterans Affairs Medical Center, White River Junction, Vermont 05001
Deborah L Ornstein - Pathology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755
Gary Kasof - Cell Signaling Technology, Danvers, Massachusetts 01923, and
Stefan Strack - Department of Pharmacology, The University of Iowa, Iowa City, Iowa 52242
Ruth W Craig - From the Departments of Pharmacology and Toxicology and the Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766, Ruth.W.Craig@Dartmouth.edu
Resource Type: Journal article
Publication Details: The Journal of biological chemistry, Vol.289(32), pp.21950-21959
DOI: 10.1074/jbc.M114.587873
PMID: 24939844
PMCID: PMC4139212
NLM abbreviation: J Biol Chem
ISSN: 0021-9258
eISSN: 1083-351X
Publisher: United States
Grant note: R01 CA057359 / NCI NIH HHS R01CA057359 / NCI NIH HHS P30 CA023108 / NCI NIH HHS
Language: English
Date published: 08/08/2014
Academic Unit: Pathology; Iowa Neuroscience Institute; Neuroscience and Pharmacology
Record Identifier: 9984040457302771

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