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Published 27 October 2003. doi:10.1083/jcb.200305007
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© The Rockefeller University Press, 0021-9525/2003/10/237 $8.00
The Journal of Cell Biology, Volume 163, Number 2, 237-243

Article

Vps27-Hse1 and ESCRT-I complexes cooperate to increase efficiency of sorting ubiquitinated proteins at the endosome



Patricia S. Bilodeau1, Stanley C. Winistorfer1, William R. Kearney3, Andrew D. Robertson2 and Robert C. Piper1

1 Department of Physiology and Biophysics, University of Iowa, Iowa City, IA 52246
2 Department of Biochemistry, University of Iowa, Iowa City, IA 52246
3 College of Medicine NMR facility, University of Iowa, Iowa City, IA 52246

Address correspondence to Robert C. Piper, Physiology 5-660 BSB, University of Iowa, Iowa City, IA 52242. Tel.: (319) 335-7842. Fax: (319) 335-7330. email: piperr{at}physiology.uiowa.edu

Ubiquitin (Ub) attachment to cell surface proteins causes their lysosomal degradation by incorporating them into lumenal membranes of multivesicular bodies (MVBs). Two yeast endosomal protein complexes have been proposed as Ub-sorting "receptors," the Vps27-Hse1 complex and the ESCRT-I complex. We used NMR spectroscopy and mutagenesis studies to map the Ub-binding surface for Vps27 and Vps23. Mutations in Ub that ablate only Vps27 binding or Vps23 binding blocked the ability of Ub to serve as an MVB sorting signal, supporting the idea that both the Vps27-Hse1 and ESCRT-I complexes interact with ubiquitinated cargo. Vps27 also bound Vps23 directly via two PSDP motifs present within the Vps27 COOH terminus. Loss of Vps27-Vps23 association led to less efficient sorting into the endosomal lumen. However, sorting of vacuolar proteases or the overall biogenesis of the MVB were not grossly affected. In contrast, disrupting interaction between Vps27 and Hse1 caused severe defects in carboxy peptidase Y sorting and MVB formation. These results indicate that both Ub-sorting complexes are coupled for efficient recognition of ubiquitinated cargo.

Key Words: endosome; ubiquitin; multivesicular body; endosome; lysosome

The online version of this article includes supplemental material.

Abbreviations used in this paper: CPY, carboxy peptidase Y; MVB, multivesicular body; Ub, ubiquitin; UEV, Ub E2 variant; UIM, Ub interaction motif.


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