title: A novel endocytosis signal related to the KKXX ER-retrieval signal.
abstract: Membrane proteins often contain a sorting signal in their cytoplasmic tail that promotes their clustering into coated vesicles at a specific cellular site. ERGIC-53 contains a cytoplasmic ER-retrieval signal, KKFF. However, overexpressed ERGIC-53 is transported to the cell surface and rapidly endocytosed. Here we report that ERGIC-53 carries a previously undescribed endocytosis signal. Surprisingly, the signal was KKFF and like the ER-retrieval signal required a C-terminal position. In fact, the minimal consensus sequence determined by substitutional mutagenesis (K-K/R-F/Y-F/Y) was related to the ER-retrieval consensus (K-K-X-X). Furthermore, we provide evidence that internalization of VIP36, a protein that cycles between plasma membrane and Golgi, is mediated by a signal at its C-terminus that matches the internalization consensus sequence. The relatedness of the two signals suggests that coatomer-mediated retrieval of proteins may be mechanistically more related to clathrin-dependent sorting than previously anticipated.
authors.affiliation: Department of Pharmacology, University of Basel, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Itin
authors.forename: F
authors.initials: F
authors.lastname: Kappeler
authors.forename: A D
authors.initials: AD
authors.lastname: Linstedt
authors.forename: H P
authors.initials: HP
authors.lastname: Hauri
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002451:Cell Compartmentation / Q000235:genetics / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D016384:Consensus Sequence; D004705:Endocytosis / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D017930:Genes, Reporter; D006056:Golgi Apparatus; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
chemical_list: D002352:Carrier Proteins; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins; D009842:Oligopeptides; D011993:Recombinant Fusion Proteins