title: Roles for trafficking and O-linked glycosylation in the turnover of model cell surface proteins.
abstract: Proteins targeted to the plasma membrane (PM) of cells are degraded at different rates. Sorting motifs contained within the cytoplasmic domains of transmembrane proteins, post-translational modifications (e.g. ubiquitination), and assembly into multiprotein or protein-lipid complexes all may affect the efficiency of endocytosis and recycling and influence the delivery to degradative compartments. Using the SNAP-tag labeling system, we examined the turnover of a model PM protein, the α chain of the interleukin-2 receptor (Tac). The surface lifetimes of SNAP-Tac fusions were influenced by their mode of entry into cells (clathrin-dependent versus clathrin-independent), their orientation in the PM (transmembrane versus glycosylphosphatidylinositol-anchored), and ubiquitination in their cytosolic domains. In addition, shedding of SNAP-Tac into the medium was greatly influenced by its O-linked glycosylation status. For a number of PM proteins, delivery to lysosomes and ectodomain shedding represent distinct parallel mechanisms to determine protein half-life.
authors.affiliation: From the Cell Biology and Physiology Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Darya
authors.initials: D
authors.lastname: Karabasheva
authors.affiliation: From the Cell Biology and Physiology Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20892 ncole@mail.nih.gov.
authors.forename: Nelson B
authors.initials: NB
authors.lastname: Cole
authors.affiliation: From the Cell Biology and Physiology Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Julie G
authors.initials: JG
authors.lastname: Donaldson
mesh_terms: D006031:Glycosylation; D006367:HeLa Cells; D006801:Humans; D053645:Interleukin-2 Receptor alpha Subunit / Q000235:genetics / Q000378:metabolism*; D007553:Isotope Labeling / Q000379:methods; D008247:Lysosomes / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology
chemical_list: C508017:IL2RA protein, human; D053645:Interleukin-2 Receptor alpha Subunit
keywords: Endocytosis; Lysosome; Plasma Membrane; Shedding; Trafficking