Originally published In Press as doi:10.1074/mcp.M800266-MCP200 on September 8, 2008.
Molecular & Cellular Proteomics 8:157-171, 2009.
© 2009 by The American Society for Biochemistry and Molecular Biology, Inc.
Research
A PP2A Phosphatase High Density Interaction Network Identifies a Novel Striatin-interacting Phosphatase and Kinase Complex Linked to the Cerebral Cavernous Malformation 3 (CCM3) Protein*,S
Marilyn Goudreaulta,b,
Lisa M. DAmbrosioa,b,c,
Michelle J. Keana,c,d,
Michael J. Mullina,e,
Brett G. Larsena,
Amy Sanchezf,
Sidharth Chaudhryc,g,
Ginny I. Chena,c,h,
Frank Sicheria,c,
Alexey I. Nesvizhskiii,
Ruedi Aebersoldf,j,
Brian Raughtk and
Anne-Claude Gingrasa,c,l
From the a Samuel Lunenfeld Research Institute at Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada, c Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada f Institute for Systems Biology, Seattle, Washington 98103, i Department of Pathology and Center for Computational Medicine and Biology, University of Michigan, Ann Arbor, Michigan 48109, j Institute of Molecular Systems Biology, ETH Zurich, Competence Center for Systems Physiology and Metabolic Diseases, and Faculty of Science, University of Zurich, CH-8093 Zurich, Switzerland, and k Ontario Cancer Institute and McLaughlin Centre for Molecular Medicine, Toronto, Ontario M5G 1L7 Canada
The serine/threonine protein phosphatases are targeted to specific subcellular locations and substrates in part via interactions with a wide variety of regulatory proteins. Understanding these interactions is thus critical to understanding phosphatase function. Using an iterative affinity purification/mass spectrometry approach, we generated a high density interaction map surrounding the protein phosphatase 2A catalytic subunit. This approach recapitulated the assembly of the PP2A catalytic subunit into many different trimeric complexes but also revealed several new protein-protein interactions. Here we define a novel large multiprotein assembly, referred to as the striatin-interacting phosphatase and kinase (STRIPAK) complex. STRIPAK contains the PP2A catalytic (PP2Ac) and scaffolding (PP2A A) subunits, the striatins (PP2A regulatory B''' subunits), the striatin-associated protein Mob3, the novel proteins STRIP1 and STRIP2 (formerly FAM40A and FAM40B), the cerebral cavernous malformation 3 (CCM3) protein, and members of the germinal center kinase III family of Ste20 kinases. Although the function of the CCM3 protein is unknown, the CCM3 gene is mutated in familial cerebral cavernous malformations, a condition associated with seizures and strokes. Our proteomics survey indicates that a large portion of the CCM3 protein resides within the STRIPAK complex, opening the way for further studies of CCM3 biology. The STRIPAK assembly establishes mutually exclusive interactions with either the CTTNBP2 proteins (which interact with the cytoskeletal protein cortactin) or a second subcomplex consisting of the sarcolemmal membrane-associated protein (SLMAP) and the related coiled-coil proteins suppressor of IKK (SIKE) and FGFR1OP2. We have thus identified several novel PP2A-containing protein complexes, including a large assembly linking kinases and phosphatases to a gene mutated in human disease.
l Holds the Canada Research Chair in Functional Proteomics. To whom correspondence should be addressed: Samuel Lunenfeld Research Inst. at Mount Sinai Hospital, 600 University Ave., Rm. 992, Toronto, Ontario M5G 1X5, Canada. Tel.: 416-586-5027; Fax: 416-586-8869; E-mail: gingras{at}lunenfeld.ca

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Copyright © 2009 by the American Society for Biochemistry and Molecular Biology.
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