title: Endolyn is a mucin-like type I membrane protein targeted to lysosomes by its cytoplasmic tail.
abstract: Endolyn (endolyn-78) is a membrane protein found in lysosomal and endosomal compartments of mammalian cells. Unlike 'classical' lysosomal membrane proteins, such as lysosome-associated membrane protein (lamp)-1, it is also present in a subapical compartment in polarized WIF-B hepatocytes. The structural features that determine sorting of endolyn are unknown. We have identified a rat endolyn cDNA by expression screening. The cDNA encodes a ubiquitously expressed type I membrane protein with a short cytoplasmic tail of 13 amino acids and many putative sites for N- and O-linked glycosylation in the predicted luminal domain. Endolyn is closely related to two human mucin-like proteins, multi-glycosylated core protein (MGC)-24 and CD164 (MGC-24v), expressed in gastric carcinoma cells and bone marrow stromal and haematopoietic precursor cells respectively. The predicted transmembrane and cytoplasmic tail domains of endolyn, as well as parts of its luminal domain, also show some similarities with lamp-1 and lamp-2. Like these and other known lysosomal membrane proteins, endolyn contains a YXXO motif at the C-terminus of its cytoplasmic tail (where O is a bulky hydrophobic amino acid), but with no preceding glycine. Nonetheless, the last ten amino acids of this tail, when transplanted on to human CD8, caused efficient targeting of the chimaeric protein to endosomes and lysosomes in transfected normal rat kidney cells.
authors.affiliation: Department of Clinical Biochemistry, Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 2XY, U.K. gi200@cus.cam.ac.uk
authors.forename: G
authors.initials: G
authors.lastname: Ihrke
authors.forename: S R
authors.initials: SR
authors.lastname: Gray
authors.forename: J P
authors.initials: JP
authors.lastname: Luzio
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD; D001483:Base Sequence; D051929:CD146 Antigen; D002451:Cell Compartmentation; D016764:Cell Polarity; D017124:Conserved Sequence; D004220:Disulfides; D051930:Endolyn; D015723:Gene Library; D008099:Liver / Q000166:cytology / Q000378:metabolism; D051907:Lysosomal Membrane Proteins; D008247:Lysosomes / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009077:Mucins / Q000235:genetics / Q000378:metabolism*; D019006:Neural Cell Adhesion Molecules; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D015703:Antigens, CD; D051929:CD146 Antigen; C497901:Cd164 protein, rat; D004220:Disulfides; D051930:Endolyn; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D009077:Mucins; D019006:Neural Cell Adhesion Molecules; D021382:Protein Sorting Signals; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins