PR65A phosphorylation regulates PP2A complex signaling.
Serine-threonine Protein phosphatase 2 A (PP2A), a member of the PPP family of phosphatases, regulates a variety of essential cellular processes, including cell-cycling, DNA replication, transcription, translation, and secondary signaling pathways. In the heart, increased PP2A activity/signaling has been linked to cardiac remodeling, contractile dysfunction and, in failure, arrythmogenicity. The core PP2A complex is a hetero-trimeric holoenzyme consisting of a 36 kDa catalytic subunit (PP2Ac); a regulatory scaffold subunit of 65 kDa (PR65A or PP2Aa); and one of at least 18 associated variable regulatory proteins (B subunits) classified into 3 families. In the present study, three in vivo sites of phosphorylation in cardiac PR65A are identified (S303, T268, S314). Using HEK cells transfected with recombinant forms of PR65A with phosphomimetic (P-PR65A) and non-phosphorylated (N-PR65A) amino acid substitutions at these sites, these phosphorylations were shown to inhibit the interaction of PR65A with PP2Ac and PP2A holoenzyme signaling. Forty-seven phospho-proteins were increased in abundance in HEK cells transfected with P-PR65A versus N-PR65A by phospho-protein profiling using 2D-DIGE analysis on phospho-enriched whole cell protein extracts. Among these proteins were elongation factor 1α (EF1A), elongation factor 2, heat shock protein 60 (HSP60), NADPH-dehydrogenase 1 alpha sub complex, annexin A, and PR65A. Compared to controls, failing hearts from the Dahl rat had less phosphorylated PR65A protein abundance and increased PP2A activity. Thus, PR65A phosphorylation is an in vivo mechanism for regulation of the PP2A signaling complex and increased PP2A activity in heart failure.
Department of Medicine and Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois, United States of America.
Kumar
K
Kotlo
Department of Oncology, University of Wisconsin, Madison, Wisconsin, United States of America.
Yongna
Y
Xing
Jesse Brown Veterans Administration, Chicago, Illinois, United States of America.
Sonia
S
Lather
Department of Medicine and Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois, United States of America.
Jean Michel
JM
Grillon
Department of Pharmacology, University of Illinois at Chicago, Chicago, Illinois, United States of America.
Keven
K
Johnson
Department of Pharmacology, University of Illinois at Chicago, Chicago, Illinois, United States of America.
Randal A
RA
Skidgel
Department of Medicine and Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois, United States of America ; Department of Physiology, University of Illinois at Chicago, Chicago, Illinois, United States of America.
R John
RJ
Solaro
Department of Medicine and Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois, United States of America ; Department of Physiology, University of Illinois at Chicago, Chicago, Illinois, United States of America ; Jesse Brown Veterans Administration, Chicago, Illinois, United States of America ; Department of Pharmacology, University of Illinois at Chicago, Chicago, Illinois, United States of America.
Robert S
RS
Danziger
D000818:Animals; D017305:Annexin A1 / Q000235:genetics / Q000378:metabolism; D018834:Chaperonin 60 / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006333:Heart Failure / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D009252:NADPH Dehydrogenase / Q000235:genetics / Q000378:metabolism; D020648:Peptide Elongation Factor 1 / Q000235:genetics / Q000378:metabolism; D020652:Peptide Elongation Factor 2 / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D055503:Protein Multimerization; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D020303:Rats, Inbred Dahl; D015398:Signal Transduction
D017305:Annexin A1; D018834:Chaperonin 60; C060293:HSPD1 protein, human; D024101:Mitochondrial Proteins; C517191:PPP2R1A protein, human; D020648:Peptide Elongation Factor 1; D020652:Peptide Elongation Factor 2; D010750:Phosphoproteins; D021122:Protein Subunits; D009252:NADPH Dehydrogenase; C514014:Ppp2ca protein, rat; D054648:Protein Phosphatase 2