Retrograde trafficking of \u03b2-dystroglycan from the plasma membrane to the nucleus

Viridiana Gracida-Jiménez,Steve J Winder,Marco S Laredo-Cisneros,Juan De Dios Gómez-López,Bulmaro Cisneros,Alejandra Vásquez-Limeta,Sarah C Gourlay,Luis Vaca,Ricardo Mondragón-González,Griselda Vélez-Aguilera,Laura A Jacobs

doi:10.1038/s41598-017-09972-x

Abstract

β-Dystroglycan (β-DG) is a transmembrane protein with critical roles in cell adhesion, cytoskeleton remodeling and nuclear architecture. This functional diversity is attributed to the ability of β-DG to target to, and conform specific protein assemblies at the plasma membrane (PM) and nuclear envelope (NE). Although a classical NLS and importin α/β mediated nuclear import pathway has already been described for β-DG, the intracellular trafficking route by which β-DG reaches the nucleus is unknown. In this study, we demonstrated that β-DG undergoes retrograde intracellular trafficking from the PM to the nucleus via the endosome-ER network. Furthermore, we provided evidence indicating that the translocon complex Sec61 mediates the release of β-DG from the ER membrane, making it accessible for importins and nuclear import. Finally, we show that phosphorylation of β-DG at Tyr890 is a key stimulus for β-DG nuclear translocation. Collectively our data describe the retrograde intracellular trafficking route that β-DG follows from PM to the nucleus. This dual role for a cell adhesion receptor permits the cell to functionally connect the PM with the nucleus and represents to our knowledge the first example of a cell adhesion receptor exhibiting retrograde nuclear trafficking and having dual roles in PM and NE.

Highlights

Viridiana Gracida-Jiménez[1], Ricardo Mondragón-González[1], Griselda Vélez-Aguilera[1], Alejandra Vásquez-Limeta[1,2], Marco S
As DG is an extensively glycosylated protein which is normally synthesized in the endoplasmic reticulum (ER) and transits the Golgi to acquire further modification, we first analyzed whether translocation of β-DG from the endoplasmic reticulum (ER) to the Golgi is a prerequisite for its subsequent nuclear localization
To support these findings with biochemical evidence, subcellular fractionation was carried out and nuclear and cytosolic fractions obtained from Brefeldin A (BFA)- or vehicle-treated cells were subjected to immunoblotting analysis, using calnexin and lamin B1 as purity markers for cytoplasmic and nuclear fractions respectively

Summary

Introduction

Viridiana Gracida-Jiménez[1], Ricardo Mondragón-González[1], Griselda Vélez-Aguilera[1], Alejandra Vásquez-Limeta[1,2], Marco S. Winder4 & Bulmaro Cisneros[1] β-Dystroglycan (β-DG) is a transmembrane protein with critical roles in cell adhesion, cytoskeleton remodeling and nuclear architecture. This functional diversity is attributed to the ability of β-DG to target to, and conform specific protein assemblies at the plasma membrane (PM) and nuclear envelope (NE). A classical NLS and importin α/β mediated nuclear import pathway has already been described for β-DG, the intracellular trafficking route by which β-DG reaches the nucleus is unknown. Implicated in the transcriptional regulation of androgen-responsive transcription factors in prostate cancer[15] Taking all this evidence into account, β-DG must be regarded as a versatile protein playing physiological roles in both, plasma membrane (PM) and nucleus. We show that phosphorylation at Tyr[890] favors the nuclear translocation of β-DG by enhancing its endosome-mediated internalization

Methods

Results

Conclusion