title: P-selectin targeting to secretory lysosomes of Rbl-2H3 cells.
abstract: The biogenesis of secretory lysosomes, which combine characteristics of both lysosomes and secretory granules, is currently of high interest. In particular, it is not clear whether delivery of membrane proteins to the secretory lysosome requires lysosomal, secretory granule, or some novel targeting determinants. Heterologous expression of P-selectin has established that this membrane protein contains targeting signals for both secretory granules and lysosomes. P-selectin is therefore an ideal probe with which to determine the signals required for targeting to secretory lysosomes. We have exploited subcellular fractionation and immunofluorescence microscopy to monitor targeting of transiently expressed wild-type and mutant horseradish peroxidase (HRP)-P-selectin chimeras to secretory lysosomes of Rbl-2H3 cells. The exposure of the HRP chimeras to intracellular proteolysis was also determined as a third monitor of secretory lysosome targeting. Our data show that HRP-P-selectin accumulates in secretory lysosomes of Rbl-2H3 cells using those cytoplasmic sequences previously found to be sufficient for targeting to conventional lysosomes. This work highlights the similar sorting signals used for targeting of membrane proteins to conventional lysosomes and secretory lysosomes.
authors.affiliation: MRC Laboratory for Molecular Cell Biology, Cell Biology Unit, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Jasber
authors.initials: J
authors.lastname: Kaur
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Cutler
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D017830:Octoxynol; D019007:P-Selectin / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000494:pharmacology; D011485:Protein Binding; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012701:Serotonin / Q000378:metabolism; D015398:Signal Transduction; D013347:Subcellular Fractions; D014162:Transfection; D014168:Transferrin / Q000378:metabolism
chemical_list: D003902:Detergents; D019007:P-Selectin; D011993:Recombinant Fusion Proteins; D014168:Transferrin; D012701:Serotonin; D011092:Polyethylene Glycols; D017830:Octoxynol; C010615:Nonidet P-40