title: A chimera of the cytoplasmic tail of the mannose 6-phosphate/IGF-II receptor and lysozyme localizes to the TGN rather than prelysosomes where the bulk of the endogenous receptor is found.
abstract: We fused the cytoplasmic and transmembrane domains of the bovine mannose 6-phosphate/IGF-II receptor (MPR) to lysozyme, a monomeric secretory protein thought to be devoid of sorting information. When the resulting chimera (lys/MPR) was transiently expressed in COS cells or stably expressed in CV1 cells, it had a predominantly intracellular distribution in the trans-Golgi region, with less than 10% present on the surface. In contrast, a similar chimera containing the transmembrane and cytoplasmic domains of the low density lipoprotein receptor (lys/LDLR) was localized to the plasma membrane, even though it endocytoses efficiently. Exchanging domains between the lys/MPR and lys/LDLR chimeras indicated that the MPR cytoplasmic domain contains the information necessary to specify the intracellular localization of the chimeric molecule. This signal must be located in the membrane-proximal third of the tail, as deletion of the last 120 residues of the 163 residue tail has no obvious effect on the distribution of lys/MPR. However, the recycling of the lys/MPR does not completely mimic that of the intact endogenous MPR, as immunofluorescence labelling shows that they are predominantly in different locations, indicating a role for the lumenal domain of the MPR in determining the steady-state distribution of the MPR itself.
authors.affiliation: Medical Research Council, Laboratory of Molecular Biology, Cambridge, UK.
authors.forename: E
authors.initials: E
authors.lastname: Conibear
authors.forename: B M
authors.initials: BM
authors.lastname: Pearse
mesh_terms: D000818:Animals; D001483:Base Sequence; D002451:Cell Compartmentation; D002460:Cell Line; D002522:Chlorocebus aethiops; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism; D004705:Endocytosis; D006056:Golgi Apparatus / Q000378:metabolism*; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D008969:Molecular Sequence Data; D009113:Muramidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017527:Receptor, IGF Type 2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011973:Receptors, LDL / Q000737:chemistry / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism*
chemical_list: D017527:Receptor, IGF Type 2; D011973:Receptors, LDL; D011993:Recombinant Fusion Proteins; D009113:Muramidase