Nuclear import of ?-dystroglycan is facilitated by ezrin-mediated cytoskeleton reorganization.

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

SUBMITTER: Vasquez-Limeta A 

PROVIDER: S-EPMC3944073 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature