Nuclear Import of [beta]-Dystroglycan Is Facilitated by Ezrin-Mediated Cytoskeleton Reorganization

• Published in: PloS one Vol. 9; no. 3; p. e90629
• Main Authors: Vásquez-Limeta, Alejandra, Wagstaff, Kylie M, Ortega, Arturo, Crouch, Dorothy H, Jans, David A, Cisneros, Bulmaro
• Format: Journal Article
• Language: English
• Published: Public Library of Science 05.03.2014
• Subjects: Analysis; Dystrophin; Utrophin
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0090629

The [beta]-dystroglycan ([beta]-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 [alpha]2/[beta]1-recognised nuclear localization signal (NLS) of [beta]-DG is also a binding site for the cytoskeletal-interacting protein ezrin, and set out to determine whether ezrin binding might modulate [beta]-DG nuclear translocation for the first time. Unexpectedly, we found that ezrin enhances rather than inhibits [beta]-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 [beta]-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 [beta]-DG concomitant with a lack of cell surface protrusions. Further, a role for the actin cytoskeleton in ezrin enhancement of [beta]-DG nuclear translocation was implicated by the observation that an ezrin variant lacking its actin-binding domain failed to enhance nuclear translocation of [beta]-DG, while disruption of the actin cytoskeleton led to a reduction in [beta]-DG nuclear localization. Finally, we show that ezrin-mediated cytoskeletal reorganization enhances nuclear translocation of the cytoplasmic but not the transmembranal fraction of [beta]-DG. This is the first study showing that cytoskeleton reorganization can modulate nuclear translocation of [beta]-DG, with the implication that [beta]-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.