title: Clathrin-coated pit-associated proteins are required for alveolar macrophage phagocytosis.
abstract: During phagocytosis, phagocytic receptors and membrane material must be inserted in the pseudopod membrane as it extends over the phagocytic target. This may require a clathrin-mediated recycling mechanism similar to that postulated for leading edge formation during cell migration. To investigate this possibility, liposomes were used to deliver to intact rat alveolar macrophages (AMs): 1) Abs to clathrin, clathrin adaptor AP-2, and hsc70, and 2) amantadine. Phagocytosis was assayed by fluorometric and colorimetric techniques. Liposome-delivered Abs to clathrin and AP-2 inhibited AM phagocytosis of zymosan-coated, fluorescent liposomes from 16.3+/-0.3 to 5.8+/-0.3, and 10.1+/-0.9 to 4.8+/-0.2 liposomes/cell (p<0.01). Similarly, liposome-delivered Ab to clathrin also inhibited AM phagocytosis of IgG-opsonized RBCs from 11.7+/-1.7 to 3.8+/-0.7 RBCs/cell (p<0.01). Amantadine, which blocks the budding of clathrin-coated vesicles, inhibited phagocytosis from 13.8+/-0.8 to 5.7+/-0.6 (p<0.01). Ab blockade of hsc70, which catalyzes clathrin turnover, also inhibited phagocytosis from 9.1+/-0.5 to 4.3+/-0.2 (p<0.01). These findings suggest that clathrin-mediated receptor/membrane recycling is required for phagocytosis.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Indiana University School of Medicine, Indianapolis 46202, USA. dperry@iupui.edu
authors.forename: D G
authors.initials: DG
authors.lastname: Perry
authors.forename: G L
authors.initials: GL
authors.lastname: Daugherty
authors.forename: W J
authors.initials: WJ
authors.lastname: Martin
mesh_terms: D000251:Adenosine Triphosphatases / Q000276:immunology; D000547:Amantadine / Q000494:pharmacology; D000818:Animals; D000906:Antibodies / Q000378:metabolism / Q000494:pharmacology; D002352:Carrier Proteins / Q000276:immunology; D002966:Clathrin / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D033922:Clathrin Heavy Chains; D003034:Coated Pits, Cell-Membrane / Q000502:physiology*; D003593:Cytoplasm / Q000276:immunology / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D005260:Female; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000276:immunology; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008081:Liposomes / Q000276:immunology; D016676:Macrophages, Alveolar / Q000737:chemistry / Q000276:immunology / Q000502:physiology*; D010587:Phagocytosis / Q000187:drug effects / Q000276:immunology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000906:Antibodies; D002352:Carrier Proteins; D002966:Clathrin; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C494373:Hspa8 protein, rat; D007166:Immunosuppressive Agents; D008081:Liposomes; D033922:Clathrin Heavy Chains; D000547:Amantadine; D000251:Adenosine Triphosphatases