title: Nuclear import of β-dystroglycan is facilitated by ezrin-mediated cytoskeleton reorganization.
abstract: The β-dystroglycan (β-DG) protein has the ability to target to multiple sites in eukaryotic cells, being a member of diverse protein assemblies including the transmembranal dystrophin-associated complex, and a nuclear envelope-localised complex that contains emerin and lamins A/C and B1. We noted that the importin α2/β1-recognised nuclear localization signal (NLS) of β-DG is also a binding site for the cytoskeletal-interacting protein ezrin, and set out to determine whether ezrin binding might modulate β-DG nuclear translocation for the first time. Unexpectedly, we found that ezrin enhances rather than inhibits β-DG nuclear translocation in C2C12 myoblasts. Both overexpression of a phosphomimetic activated ezrin variant (Ez-T567D) and activation of endogenous ezrin through stimulation of the Rho pathway resulted in both formation of actin-rich surface protrusions and significantly increased nuclear translocation of β-DG as shown by quantitative microscopy and subcellular fractionation/Western analysis. In contrast, overexpression of a nonphosphorylatable inactive ezrin variant (Ez-T567A) or inhibition of Rho signaling, decreased nuclear translocation of β-DG concomitant with a lack of cell surface protrusions. Further, a role for the actin cytoskeleton in ezrin enhancement of β-DG nuclear translocation was implicated by the observation that an ezrin variant lacking its actin-binding domain failed to enhance nuclear translocation of β-DG, while disruption of the actin cytoskeleton led to a reduction in β-DG nuclear localization. Finally, we show that ezrin-mediated cytoskeletal reorganization enhances nuclear translocation of the cytoplasmic but not the transmembranal fraction of β-DG. This is the first study showing that cytoskeleton reorganization can modulate nuclear translocation of β-DG, with the implication that β-DG can respond to cytoskeleton-driven changes in cell morphology by translocating from the cytoplasm to the nucleus to orchestrate nuclear processes in response to the functional requirements of the cell.
authors.affiliation: Departamento de Genética y Biología Molecular, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), México D.F., Mexico.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Vásquez-Limeta
authors.affiliation: Nuclear Signalling Laboratory, Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
authors.forename: Kylie M
authors.initials: KM
authors.lastname: Wagstaff
authors.affiliation: Departamento de Genética y Biología Molecular, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), México D.F., Mexico.
authors.forename: Arturo
authors.initials: A
authors.lastname: Ortega
authors.affiliation: School of Dentistry, University of Dundee, Dundee, Scotland, United Kingdom.
authors.forename: Dorothy H
authors.initials: DH
authors.lastname: Crouch
authors.affiliation: Nuclear Signalling Laboratory, Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
authors.forename: David A
authors.initials: DA
authors.lastname: Jans
authors.affiliation: Departamento de Genética y Biología Molecular, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), México D.F., Mexico.
authors.forename: Bulmaro
authors.initials: B
authors.lastname: Cisneros
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D021581:Active Transport, Cell Nucleus; D000818:Animals; D019921:Biotinylation; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000502:physiology*; D049030:Dystroglycans / Q000378:metabolism*; D051379:Mice; D032448:Myoblasts, Skeletal / Q000378:metabolism; D015398:Signal Transduction; D028961:beta Karyopherins / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000502:physiology; D000099149:Ezrin
chemical_list: D003598:Cytoskeletal Proteins; D049030:Dystroglycans; D028961:beta Karyopherins; D020741:rho GTP-Binding Proteins; D000099149:Ezrin