A Mammalian Homolog of Yeast MOB1 Is Both a Member and a Putative Substrate of Striatin Family-Protein Phosphatase 2A Complexes

• Type of Material: Article
• Authors: Carlos S Moreno, Emory University; William S. Lane, Harvard University; David C Pallas, Emory University
• Language: English
• Date: 2001-06-29
• Publisher: American Society for Biochemistry and Molecular Biology
• Publication Version: Final Published Version
• Copyright Statement: © 2001 by The American Society for Biochemistry and Molecular Biology, Inc.
• Final Published Version (URL): http://www.jbc.org/content/276/26/24253.long
• Title of Journal or Parent Work: Journal of Biological Chemistry
• ISSN: 0021-9258
• Volume: 276
• Issue: 26
• Start Page: 24253
• End Page: 24260
• Grant/Funding Information: This work was supported by National Institutes of Health Grant CA57327. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
• Research Categories: Biology, General; Chemistry, Biochemistry

Abstract

Striatin and S/G2 nuclear autoantigen (SG2NA) are related proteins that contain membrane binding domains and associate with protein phosphatase 2A (PP2A) and many additional proteins that may be PP2A regulatory targets. Here we identify a major member of these complexes as class II mMOB1, a mammalian homolog of the yeast protein MOB1, and show that its phosphorylation appears to be regulated by PP2A. Yeast MOB1 is critical for cytoskeletal reorganization during cytokinesis and exit from mitosis. We show that mMOB1 associated with PP2A is not detectably phosphorylated in asynchronous murine fibroblasts. However, treatment with the PP2A inhibitor okadaic acid induces phosphorylation of PP2A-associated mMOB1 on serine. Moreover, specific inhibition of PP2A also results in hyperphosphorylation of striatin, SG2NA, and three unidentified proteins, suggesting that these proteins may also be regulated by PP2A. Indirect immunofluorescence produced highly similar staining patterns for striatin, SG2NA, and mMOB1, with the highest concentrations for each protein adjacent to the nuclear membrane. We also present evidence that these complexes may interact with each other. These data are consistent with a model in which PP2A may regulate mMOB1, striatin, and SG2NA to modulate changes in the cytoskeleton or interactions between the cytoskeleton and membrane structures.