title: Lysine-63-linked ubiquitination is required for endolysosomal degradation of class I molecules.
abstract: MHC class I molecules display peptides from endogenous and viral proteins for immunosurveillance by cytotoxic T lymphocytes (CTL). The importance of the class I pathway is emphasised by the remarkable strategies employed by different viruses to downregulate surface class I and avoid CTL recognition. The K3 gene product from Kaposi's sarcoma-associated herpesvirus (KSHV) is a viral ubiquitin E3 ligase which ubiquitinates and degrades cell surface MHC class I molecules. We now show that modification of K3-associated class I by lysine-63-linked polyubiquitin chains is necessary for their efficient endocytosis and endolysosomal degradation and present three lines of evidence that monoubiquitination of class I molecules provides an inefficient internalisation signal. This lysine-63-linked polyubiquitination requires both UbcH5b/c and Ubc13-conjugating enzymes for initiating mono- and subsequent polyubiquitination of class I, and the clathrin-dependent internalisation is mediated by the epsin endocytic adaptor. Our results explain how lysine-63-linked polyubiquitination leads to degradation by an endolysosomal pathway and demonstrate a novel mechanism for endocytosis and endolysosomal degradation of class I, which may be applicable to other receptors.
authors.affiliation: Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge, UK.
authors.forename: Lidia M
authors.initials: LM
authors.lastname: Duncan
authors.forename: Siân
authors.initials: S
authors.lastname: Piper
authors.forename: Roger B
authors.initials: RB
authors.lastname: Dodd
authors.forename: Mark K
authors.initials: MK
authors.lastname: Saville
authors.forename: Chris M
authors.initials: CM
authors.lastname: Sanderson
authors.forename: J Paul
authors.initials: JP
authors.lastname: Luzio
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Lehner
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D002966:Clathrin / Q000502:physiology; D015536:Down-Regulation; D004705:Endocytosis; D011992:Endosomes / Q000502:physiology*; D006367:HeLa Cells; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008239:Lysine / Q000502:physiology*; D008247:Lysosomes / Q000502:physiology*; D025821:Polyubiquitin / Q000235:genetics; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000235:genetics; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism / Q000502:physiology*; D014764:Viral Proteins / Q000378:metabolism
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D002966:Clathrin; D015395:Histocompatibility Antigens Class I; C456022:K3 protein, Kaposi's sarcoma-associated herpesvirus; D011993:Recombinant Fusion Proteins; D025801:Ubiquitin; D014764:Viral Proteins; C114154:epsin; D025821:Polyubiquitin; C097309:UBE2D2 protein, human; C097310:UBE2D3 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D008239:Lysine