title: Endocytosis and trafficking of human lactoferrin in macrophage-like human THP-1 cells (1).
abstract: Different cell types have been reported to internalize lactoferrin (Lf) by specific or nonspecific receptors. Our studies focused on the endocytic pathway of human Lf in macrophage-like THP-1 cells. Lactoferrin was found to be internalized by THP-1 cells differentiated with  phorbol myristate acetate. Incubation of cells with chlorpromazine and dansylcadaverine, inhibitors of clathrin-dependent endocytosis, led to a 50% inhibition of Lf internalization compared with untreated cells. Bafilomycin A1 and NH(4)Cl treatment also resulted in 40%-60% inhibition, respectively, suggesting that the internalization of Lf may partly be mediated by acidic endosome-like organelles. Endocytic uptake of Lf was also cholesterol-dependent, as shown by methyl-β-cyclodextrin or nystatin treatment of the cells prior to internalization. Partial colocalization of Lf and EEA-1, a marker specific for early endosomes, could be observed. Colocalization of Lf with a specific endoplasmic reticulum marker was also detected. Our results suggest that Lf is internalized mainly by the clathrin-dependent pathway in THP-1 cells and targets the ER. The physiological consequences of this intracellular trafficking will be the subject of future investigations.
authors.affiliation: Institute of Biochemistry of the Romanian Academy, Spl. Independentei 296, Bucharest 17 060031, Romania.
authors.forename: Paula
authors.initials: P
authors.lastname: Florian
authors.forename: Alina
authors.initials: A
authors.lastname: Macovei
authors.forename: Livia
authors.initials: L
authors.lastname: Sima
authors.forename: Norica
authors.initials: N
authors.lastname: Nichita
authors.forename: Inger
authors.initials: I
authors.lastname: Mattsby-Baltzer
authors.forename: Anca
authors.initials: A
authors.lastname: Roseanu
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D002103:Cadaverine / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D002746:Chlorpromazine / Q000494:pharmacology; D002784:Cholesterol / Q000502:physiology; D004705:Endocytosis / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000378:metabolism; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007781:Lactoferrin / Q000378:metabolism*; D018942:Macrolides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D021381:Protein Transport / Q000187:drug effects
chemical_list: D018942:Macrolides; D000643:Ammonium Chloride; C040929:bafilomycin A1; D002784:Cholesterol; D007781:Lactoferrin; C008542:monodansylcadaverine; D002103:Cadaverine; D002746:Chlorpromazine