Flat clathrin coats on endosomes mediate degradative protein sorting by scaffolding Hrs in dynamic microdomains

J Cell Sci. 2006 Jun 15;119(Pt 12):2414-24. doi: 10.1242/jcs.02978. Epub 2006 May 23.

Abstract

Endocytosed membrane proteins that are destined for degradation in lysosomes are ubiquitylated and recognised by sorting complexes on endosome membranes. The ubiquitin-binding sorting component Hrs as well as ubiquitylated cargo are enriched in a characteristic flat clathrin coat on the endosome membrane. The function of clathrin within this coat has not been investigated. Here, we show that both clathrin and the clathrin-box motif of Hrs are required for the clustering of Hrs into restricted microdomains. The C-terminus of Hrs, which contains the clathrin-box, is sufficient to redirect a phosphatidylinositol(3)-phosphate-binding protein into the Hrs- and clathrin-containing microdomains. Although these microdomains show little lateral diffusion in the membrane, they are dynamic structures that exchange Hrs and clathrin with similar kinetics, and acquire the downstream sorting component Tsg101. The clathrin-mediated clustering is essential for the function of Hrs in degradative protein sorting. We conclude that clathrin is responsible for concentrating Hrs in endosomal microdomains specialised for recognition of ubiquitylated membrane proteins, thus enabling efficient sorting of cargo into the degradative pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Cell Membrane / metabolism
  • Cell Membrane / ultrastructure
  • Cells, Cultured
  • Clathrin / metabolism*
  • Clathrin-Coated Vesicles / metabolism
  • Clathrin-Coated Vesicles / ultrastructure
  • DNA-Binding Proteins / metabolism
  • Endosomal Sorting Complexes Required for Transport
  • Endosomes / metabolism*
  • Endosomes / ultrastructure
  • Epidermal Growth Factor / metabolism
  • ErbB Receptors / metabolism
  • HeLa Cells
  • Humans
  • Kinetics
  • Membrane Microdomains / metabolism*
  • Membrane Microdomains / ultrastructure
  • Membrane Proteins / metabolism
  • Phosphoproteins / metabolism*
  • Protein Transport
  • Time Factors
  • Transcription Factors / metabolism
  • Vesicular Transport Proteins / metabolism

Substances

  • Clathrin
  • DNA-Binding Proteins
  • Endosomal Sorting Complexes Required for Transport
  • Membrane Proteins
  • Phosphoproteins
  • Transcription Factors
  • Tsg101 protein
  • Vesicular Transport Proteins
  • early endosome antigen 1
  • hepatocyte growth factor-regulated tyrosine kinase substrate
  • Epidermal Growth Factor
  • ErbB Receptors