Cited by 95Protein Tyrosine PhosphatasesProtein Kinase Regulation and GTPase SignalingSignaling Pathways in Disease

Characterization of the Aalpha and Abeta subunit isoforms of protein phosphatase 2A: Differences in expression, subunit interaction, and evolution

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ZHOU, Jin, PHAM, Huong T., RUEDIGER, Ralf, WALTER, Gernot·2003·Biochemical Journal

Abstract

Protein phosphatase 2A (PP2A) is very versatile owing to a large number of regulatory subunits and its ability to interact with numerous other proteins. The regulatory A subunit exists as two closely related isoforms designated Aalpha and Abeta. Mutations have been found in both isoforms in a variety of human cancers. Although Aalpha has been intensely studied, little is known about Abeta. We generated Abeta-specific antibodies and determined the cell cycle expression, subcellular distribution, and metabolic stability of Abeta in comparison with Aalpha. Both forms were expressed at constant levels throughout the cell cycle, but Aalpha was expressed at a much higher level than Abeta. Both forms were found predominantly in the cytoplasm, and both had a half-life of approx. 10 h. However, Aalpha and Abeta differed substantially in their expression patterns in normal tissues and in tumour cell lines. Whereas Aalpha was expressed at similarly high levels in all tissues and cell lines, Abeta expression varied greatly. In addition, in vivo studies with epitope-tagged Aalpha and Abeta subunits demonstrated that Abeta is a markedly weaker binder of regulatory B and catalytic C subunits than Aalpha. Construction of phylogenetic trees revealed that the conservation of Aalpha during the evolution of mammals is extraordinarily high in comparison with both Abeta and cytochrome c, suggesting that Aalpha is involved in more protein-protein interactions than Abeta. We also measured the binding of polyoma virus middle tumour antigen and simian virus 40 (SV40) small tumour antigen to Aalpha and Abeta. Whereas both isoforms bound polyoma virus middle tumour antigen equally well, only Aalpha bound SV40 small tumour antigen.

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  • PP2A/Aα is expressed in many tissues, whereas PP2A/Aβ is mostly expressed in testis.

    “The tissue-specific expression of the two isoforms of PP2A/A is variable too, as the PP2A/Aα isoform is expressed across many tissue types, while the PP2A/Aβ isoform is mostly expressed in the testis (Zhou et al., 2003).”

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Authors
ZHOU, J., PHAM, H. T., RUEDIGER, R., & WALTER, G.
Affiliations
University of California San Diego (US)
Venue
Biochemical Journal
Published
2003-01-15
Volume
369
Issue
2
Pages
387-398
ISSN
  • 0264-6021 (ISSN-L)
  • 1470-8728
OpenAlex
W2066604078
Cited by
95
References
40
Citations by year
2025: 4 · 2023: 1 · 2022: 2 · 2021: 2 · 2020: 3 · 2019: 7 · 2018: 2 · 2017: 4 · 2016: 2 · 2015: 3 · 2014: 10 · 2013: 6 · 2012: 6
FWCI
1.72
Type
journal article
Language
en
Open access
Locations
  • Biochemical Journal (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • Tobacco-Related Disease Research Program
  • University of California, San Diego
  • National Cancer Institute (CA-36111, R01CA036111)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Protein Tyrosine Phosphatases
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Protein Kinase Regulation and GTPase Signaling
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Signaling Pathways in Disease
Keywords
protein phosphatase 2A, subunit interactions, protein-protein interaction, subcellular localization, protein stability, phylogenetic conservation, cancer mutations
MeSH terms
Animals, Antibodies, Antigens, Viral, Cell Cycle, Cell Separation, Cytochrome c Group, Enzyme Stability, Flow Cytometry, Humans, Isoenzymes, Multienzyme Complexes, Phosphoprotein Phosphatases, Phylogeny, Protein Binding, Tissue Distribution, Tumor Cells, Cultured, Gene Expression Regulation, Enzymologic, Evolution, Molecular, Protein Subunits, Protein Phosphatase 2

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