title: The role of phosphoinositide 3-kinase in the sorting and transport of newly synthesized tyrosinase-related protein-1 (TRP-1).
abstract: Tyrosinase-related protein-1 (TRP-1) is a 75 kDa type-1 transmembrane glycoprotein localized to the melanosome. The mechanism by which newly synthesized TRP-1 reaches its ultimate destination is currently unknown, but has been speculated to occur via the endosomal pathway. Recently, it has been shown that phosphatidylinositide (PI) 3-kinase is involved in various cellular functions, including regulating the constitutive movement of proteins from one intracellular compartment to another; however, whether PI 3-kinase participates in the trafficking of proteins such as TRP-1 to the melanosome is unknown. In this study we investigate the role of PI 3-kinase on the trafficking of TRP-1 in human melanoma MeWo cells using wortmannin, a potent inhibitor of PI 3-kinase. Our investigations demonstrate that wortmannin interferes with the membrane trafficking of TRP-1 in MeWo cells, and that it specifically results in the redistribution of the protein within a novel vesicular compartment with characteristics of the endosomal and lysosomal compartments [positive for LAMP-1, and partially positive for CD63 and cation-independent mannose 6-phosphate receptors (CI-M6PR)], and is accessible to internalized proteins such as immunoglobulins. Movement within this novel compartment is microtubule and GTPase dependent. These findings have led us to postulate that TRP-1 is sorted from the trans-Golgi network to a compartment in the vicinity of late endosomes, trafficking from which to the melanosome appears to be dependent on PI 3-kinase as it is blocked by wortmannin.
authors.affiliation: Division of Dermatology and Cutaneous Sciences, University of Alberta, Edmonton, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Chen
authors.forename: T G
authors.initials: TG
authors.lastname: Salopek
authors.forename: K
authors.initials: K
authors.lastname: Jimbow
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D001692:Biological Transport; D020126:Brefeldin A / Q000494:pharmacology; D011992:Endosomes / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000502:physiology; D019204:GTP-Binding Proteins / Q000502:physiology; D006801:Humans; D008247:Lysosomes / Q000502:physiology; D008562:Membrane Glycoproteins; D008870:Microtubules / Q000502:physiology; D010088:Oxidoreductases; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D011506:Proteins / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000502:physiology; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014617:Vacuoles / Q000378:metabolism; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D020126:Brefeldin A; D004791:Enzyme Inhibitors; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D008562:Membrane Glycoproteins; D010088:Oxidoreductases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011500:Protein Synthesis Inhibitors; D011506:Proteins; D006180:Proton-Translocating ATPases; D000077191:Wortmannin; C489799:TYRP1 protein, human; C064056:tyrosinase-related protein-1