title: Galectin-3 endocytosis by carbohydrate independent and dependent pathways in different macrophage like cell types.
abstract: BACKGROUND
  Galectin-3 (the Mac-2 antigen) is abundantly expressed in both macrophage like cells and certain non-macrophage cells. We have studied endocytosis of galectin-3 as one important step relevant for its function, and compared it between variants of a macrophage like cell line, and non-macrophage cells.
  
  
  METHODS
  Endocytosis of galectin-3 was observed by fluorescence microscopy and measured by flow cytometry. The endocytosis mechanism was analysed using galectin-3 mutants, galectin-3 inhibitors and endocytic pathways inhibitors in the human leukaemia THP-1 cell line differentiated into naïve (M0), classical (M1) or alternatively activated (M2) macrophage like cells, and the non-macrophage cell lines HFL-1 fibroblasts and SKBR3 breast carcinoma.
  
  
  RESULTS
  Galectin-3 endocytosis in non-macrophage cells and M2 cells was blocked by lactose and a potent galectin-3 inhibitor TD139, and also by the R186S mutation in the galectin-3 carbohydrate recognition domain (CRD). In M1 cells galectin-3 endocytosis could be inhibited only by chlorpromazine and by interference with the non-CRD N-terminal part of galectin-3. In all the cell types galectin-3 entered early endosomes within 5-10 min, to be subsequently targeted mainly to non-degradative vesicles, where it remained even after 24 h.
  
  
  CONCLUSIONS
  Galectin-3 endocytosis in M1 cells is receptor mediated and carbohydrate independent, while in M2 cells it is CRD mediated, although the non-CRD galectin-3 domain is also involved. General significance The demonstration that galectin-3 endocytosis in M1 macrophages is carbohydrate independent and different from M2 macrophages and non-macrophage cells, suggests novel, immunologically significant interactions between phagocytic cells, galectin-3 and its ligands.
authors.affiliation: Section MIG (Microbiology, Immunology, Glycobiology), Department of Laboratory Medicine, Lund University, 223 62 Lund, Sweden. adrianalepur@gmail.com
authors.forename: Adriana
authors.initials: A
authors.lastname: Lepur
authors.forename: Michael C
authors.initials: MC
authors.lastname: Carlsson
authors.forename: Ruđer
authors.initials: R
authors.lastname: Novak
authors.forename: Jerka
authors.initials: J
authors.lastname: Dumić
authors.forename: Ulf J
authors.initials: UJ
authors.lastname: Nilsson
authors.forename: Hakon
authors.initials: H
authors.lastname: Leffler
mesh_terms: D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D002241:Carbohydrates / Q000494:pharmacology*; D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004705:Endocytosis / Q000187:drug effects*; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D037502:Galectin 3 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D002241:Carbohydrates; D037502:Galectin 3; D012333:RNA, Messenger