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Journal of Cellular Biochemistry

Characterization of an Importin α/β-recognized nuclear localization signal in β-dystroglycan

Authors

  • Bárbara Lara-Chacón,

    1. Department of Genetics and Molecular Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN), Mexico City 07300, Mexico
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  • Mario Bermúdez de León,

    1. Department of Genetics and Molecular Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN), Mexico City 07300, Mexico
    2. Division of Genetics, Molecular Biology Laboratory, Northeast Biomedical Research Center, Mexican Social Security Institute (IMSS), Monterrey, Nuevo Leon 64720, Mexico
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  • Daniel Leocadio,

    1. Department of Genetics and Molecular Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN), Mexico City 07300, Mexico
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  • Pablo Gómez,

    1. Department of Genetics and Molecular Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN), Mexico City 07300, Mexico
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  • Lizeth Fuentes-Mera,

    1. Department of Genetics and Molecular Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN), Mexico City 07300, Mexico
    2. Department of Molecular Biology and Histocompatibility, Hospital General “Manuel Gea Gonzalez”, Mexico City 14080, Mexico
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  • Ivette Martínez-Vieyra,

    1. Department of Genetics and Molecular Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN), Mexico City 07300, Mexico
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  • Arturo Ortega,

    1. Department of Genetics and Molecular Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN), Mexico City 07300, Mexico
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  • David A. Jans,

    Corresponding author
    1. Department of Biochemistry and Molecular Biology, Nuclear Signalling Laboratory, Monash University, Clayton, VIC 3800, Australia
    • Department of Biochemistry and Molecular Biology, Monash University, Building 77, Monash, VIC 3800, Australia.
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  • Bulmaro Cisneros

    Corresponding author
    1. Department of Genetics and Molecular Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN), Mexico City 07300, Mexico
    • Av. IPN 2508, Col. San Pedro Zacatenco, Deleg. Gustavo A. Madero, 07360 Mexico City, Mexico.
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  • Bárbara Lara-Chacón and Mario Bermúdez de León contributed equally to this study.

Abstract

β-dystroglycan (β-DG) is a widely expressed transmembrane protein that plays important roles in connecting the extracellular matrix to the cytoskeleton, and thereby contributing to plasma membrane integrity and signal transduction. We previously observed nuclear localization of β-DG in cultured cell lines, implying the existence of a nuclear targeting mechanism that directs it to the nucleus instead of the plasma membrane. In this study, we delineate the nuclear import pathway of β-DG, characterizing a functional nuclear localization signal (NLS) in the β-DG cytoplasmic domain, within amino acids 776–782. The NLS either alone or in the context of the whole β-DG protein was able to target the heterologous GFP protein to the nucleus, with site-directed mutagenesis indicating that amino acids R779 and K780 are critical for NLS functionality. The nuclear transport molecules Importin (Imp)α and Impβ bound with high affinity to the NLS of β-DG and were found to be essential for NLS-dependent nuclear import in an in vitro reconstituted nuclear transport assay; cotransfection experiments confirmed the dependence on Ran for nuclear accumulation. Intriguingly, experiments suggested that tyrosine phosphorylation of β-DG may result in cytoplasmic retention, with Y892 playing a key role. β-DG thus follows a conventional Impα/β-dependent nuclear import pathway, with important implications for its potential function in the nucleus. J. Cell. Biochem. 110: 706–717, 2010. © 2010 Wiley-Liss, Inc.

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