Proteomic studies of PP2A-B56gamma1 phosphatase complexes reveal phosphorylation-regulated partners in cardiac local signaling

J Proteome Res. 2007 Sep;6(9):3433-42. doi: 10.1021/pr060619l. Epub 2007 Jul 31.

Abstract

Defects of kinase-phosphatase signaling in cardiac myocytes contribute to human heart disease. The activity of one phosphatase, PP2A, is governed by B targeting subunits, including B56gamma1, expressed in heart cells. As the role of PP2A/B56gamma1 on the heart function remains largely unknown, this study sought to identify protein partners through unbiased, affinity purification-based proteomics combined with the functional validation. The results reveal multiple interactors that are localized in strategic cardiac sites to participate in Ca2+ homeostasis and gene expression, exemplified by the Ca pump, SERCA2a, and the splicing factor ASF/SF2. These results are corroborated by confocal imaging where adenovirally overexpressed B56gamma1 is found in z-line/t-tubule region and nuclear speckles. Importantly, overexpression of B56gamma1 in cultured myocytes dramatically impairs cell contractility. These results provide a global view of B56gamma1-regulated local signaling and heart function.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alternative Splicing
  • Chromatography, Liquid
  • Humans
  • Mass Spectrometry
  • Microscopy, Confocal
  • Myocardial Contraction
  • Myocardium / metabolism*
  • Myocytes, Cardiac / metabolism
  • Nuclear Proteins / metabolism
  • Phosphoprotein Phosphatases / chemistry*
  • Phosphorylation
  • Protein Phosphatase 2
  • Protein Structure, Tertiary
  • Proteomics / methods*
  • RNA-Binding Proteins
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism
  • Serine-Arginine Splicing Factors
  • Signal Transduction

Substances

  • Nuclear Proteins
  • RNA-Binding Proteins
  • Serine-Arginine Splicing Factors
  • PPP2R5C protein, human
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 2
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases