Journal article
Critical role for protein phosphatase 2A heterotrimers in mammalian cell survival
The Journal of biological chemistry, Vol.279(46), pp.47732-47739
11/12/2004
DOI: 10.1074/jbc.M408015200
PMID: 15364932
Abstract
The predominant forms of protein phosphatase 2A (PP2A), one of the major Ser/Thr phosphatases, are dimers of catalytic (C) and scaffolding (A) subunits and trimers with an additional variable regulatory subunit. In mammals, catalytic and scaffolding subunits are encoded by two genes each (alpha/beta), whereas three gene families (B, B', and B'') with a total of 12 genes contribute PP2A regulatory subunits. We generated stable PC12 cell lines in which the major scaffolding Aalpha subunit can be knocked down by inducible RNA interference (RNAi) to study its role in cell viability. Aalpha RNAi decreased total PP2A activity as well as protein levels of C, B, and B' but not B'' subunits. Inhibitor experiments indicate that monomeric C and B subunits are degraded by the proteosome. Knock-down of Aalpha triggered cell death by redundant apoptotic and non-apoptotic mechanisms because the inhibition of RNAi-associated caspase activation failed to stall cell death. PP2A holoenzymes positively regulate survival kinase signaling, because RNAi reduced basal and epidermal growth factor-stimulated Akt phosphorylation. RNAi-resistant Aalpha cDNAs rescued RNAi-induced loss of the C subunit, and Aalpha point mutants prevented regulatory subunit degradation as predicted from each mutant's binding specificity. In transient, stable, and stable-inducible rescue experiments, both wild-type Abeta and Aalpha mutants capable of binding to at least one family of regulatory subunits were able to delay Aalpha RNAi-induced death of PC12 cells. However, only the expression of wild-type Aalpha restored viability completely. Thus, heterotrimeric PP2A holoenzymes containing the Aalpha subunit and members of all three regulatory subunit families are necessary for mammalian cell viability.
Details
- Title: Subtitle
- Critical role for protein phosphatase 2A heterotrimers in mammalian cell survival
- Creators
- Stefan Strack - Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA. stefan-strack@uiowa.eduJ Thomas CribbsLisa Gomez
- Resource Type
- Journal article
- Publication Details
- The Journal of biological chemistry, Vol.279(46), pp.47732-47739
- DOI
- 10.1074/jbc.M408015200
- PMID
- 15364932
- NLM abbreviation
- J Biol Chem
- ISSN
- 0021-9258
- eISSN
- 1083-351X
- Publisher
- United States
- Grant note
- NS43254 / NINDS NIH HHS
- Language
- English
- Date published
- 11/12/2004
- Academic Unit
- Pathology; Iowa Neuroscience Institute; Neuroscience and Pharmacology; Ophthalmology and Visual Sciences
- Record Identifier
- 9984024408102771
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