Endosomal Transport of ErbB-2: Mechanism for Nuclear Entry of the Cell Surface Receptor

Abstract

The cell membrane receptor ErbB-2 migrates to the nucleus. However, the mechanism of its nuclear translocation is unclear. Here, we report a novel mechanism of its nuclear localization that involves interaction with the transport receptor importin β1, nuclear pore protein Nup358, and a host of players in endocytic internalization. Knocking down importin β1 using small interfering RNA oligonucleotides or inactivation of small GTPase Ran by RanQ69L, a dominant-negative mutant of Ran, causes a nuclear transport defect of ErbB-2. Mutation of a putative nuclear localization signal in ErbB-2 destroys its interaction with importin β1 and arrests nuclear translocation, while inactivation of nuclear export receptor piles up ErbB-2 within the nucleus. Additionally, blocking of internalization by a dominant-negative mutant of dynamin halts its nuclear localization. Thus, the cell membrane-embedded ErbB-2, through endocytosis using the endocytic vesicle as a vehicle, importin β1 as a driver and Nup358 as a traffic light, migrates from the cell surface to the nucleus. This novel mechanism explains how a receptor tyrosine kinase on the cell surface can be translocated into the nucleus. This pathway may serve as a general mechanism to allow direct communication between cell surface receptors and the nucleus, and our findings thus open a new era in understanding direct trafficking between the cell membrane and nucleus.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://mcb.asm.org/.

ACKNOWLEDGMENTS

We thank Karsten Weis, Mark A. McNiven, and Alexandre Benmerah for their generosity in providing pQE-Ran, pQE-RanQ69L, GFP-tagged dynamin 2, GFP-tagged K44A dynamin 2, and GFP-tagged EPS15.

This work was supported by grants from NIH, RO1 CA109311 and PO1 CA099031, and The National Breast Cancer Research Foundation, Inc. (to M.-C.H.) and by M. D. Anderson Cancer Center supporting grant CA16672.