title: Recruitment of UBPY and ESCRT exchange drive HD-PTP-dependent sorting of EGFR to the MVB.
abstract: BACKGROUND
  Sorting ubiquitinated epidermal growth factor receptor (EGFR) to the intralumenal vesicles of the multivesicular body requires the coordinated action of several ESCRT complexes. A central question is how EGFR transits vectorially from early, ubiquitin-binding ESCRTs to the final complex, ESCRT-III, such that cargo sequestration is coupled with intralumenal vesicle formation.
  
  
  RESULTS
  We show that the ESCRT accessory protein HD-PTP/PTPN23 associates with EGFR and combines with the deubiquitinating enzyme UBPY/USP8 to transfer EGFR from ESCRT-0 to ESCRT-III and drive EGFR sorting to intralumenal vesicles. HD-PTP binds ESCRT-0 via two interactions with the STAM2 subunit. First, the HD-PTP Bro1 domain binds the core domain of STAM2. This is competed by the ESCRT-III subunit CHMP4B, which binds an overlapping site on HD-PTP Bro1. Second, a proline-rich peptide in HD-PTP binds the SH3 domain of STAM2. Similar proline-rich peptides on UBPY also bind STAM2 SH3 to facilitate EGFR deubiquitination. Hence, locally recruited UBPY would be expected to compete with HD-PTP for STAM2 binding at this second site. Indeed, we show that HD-PTP recruits UBPY to EGFR. Association of UBPY with HD-PTP involves UBPY interacting with HD-PTP-bound CHMP4B, as well as additional interaction(s) between UBPY and HD-PTP.
  
  
  CONCLUSIONS
  This study identifies HD-PTP as a central coordinator of the ESCRT pathway for EGFR. Based on these studies, we propose a model whereby the concerted recruitment of CHMP4B and UBPY to HD-PTP and the engagement of UBPY by STAM2 displaces ESCRT-0 from HD-PTP, deubiquitinates EGFR, and releases ESCRT-0 from cargo in favor of ESCRT-III.
authors.affiliation: University of Manchester, Manchester M13 9PT, UK.
authors.forename: Nazim
authors.initials: N
authors.lastname: Ali
authors.forename: Ling
authors.initials: L
authors.lastname: Zhang
authors.forename: Sandra
authors.initials: S
authors.lastname: Taylor
authors.forename: Alex
authors.initials: A
authors.lastname: Mironov
authors.forename: Sylvie
authors.initials: S
authors.lastname: Urbé
authors.forename: Philip
authors.initials: P
authors.lastname: Woodman
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D055032:Electron Microscope Tomography; D010450:Endopeptidases / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D057146:Multivesicular Bodies / Q000378:metabolism*; D021381:Protein Transport; D054558:Protein Tyrosine Phosphatases, Non-Receptor / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D020798:Two-Hybrid System Techniques; D043222:Ubiquitin Thiolesterase / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D056827:Endosomal Sorting Complexes Required for Transport; C491647:STAM2 protein, human; C512478:EGFR protein, human; D066246:ErbB Receptors; C114102:PTPN23 protein, human; D054558:Protein Tyrosine Phosphatases, Non-Receptor; D010450:Endopeptidases; C541534:USP8 protein, human; D043222:Ubiquitin Thiolesterase