title: A Rab11-containing rapidly recycling compartment in macrophages that promotes phagocytosis.
abstract: Macrophages are specialized cells of the immune system that exhibit a prodigious capacity for phagocytosis. The ability of macrophages to internalize a substantial proportion of their plasma membrane during phagocytosis indicates that they possess a mechanism for the rapid renewal of plasma membrane. We examined the role of endocytic membrane recycling in promoting phagocytosis. In contrast to many other cell types, macrophages lack a morphologically distinct peri-centriolar recycling compartment but instead demonstrate an extensive network of transferrin receptor-positive tubules and vesicles that participated in recycling. The rate of transferrin recycling in thioglycollate-elicited murine peritoneal macrophages (thio-macrophages) was exceedingly rapid, with exocytic rate constants that were 2- to 3-fold higher than those of most other cells. Because the GTPase Rab11 has been implicated in transferrin recycling in other cells, we determined its role in transferrin recycling and phagocytosis in macrophages. Macrophages expressing epitope-tagged Rab11 demonstrated the presence of Rab11 in several intracellular membrane compartments, including endosomes and nascent phagosomes. Expression of Rab11 25N, a GTP binding-deficient allele of Rab11, led to a decreased rate of transferrin efflux and impaired Fc(gamma)R-mediated phagocytosis, where Fc(gamma)R is the receptor for the Fc portion of IgG. In contrast, expression of Rab11 70L, a GTPase-deficient allele of Rab11, led to an increased rate of transferrin efflux and enhanced phagocytosis. We conclude that macrophages have adapted a rapidly mobilizable, endocytic compartment to enhance phagocytosis. Rab11 participates in the recruitment of this compartment to the macrophage cell surface.
authors.affiliation: Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
authors.forename: D
authors.initials: D
authors.lastname: Cox
authors.forename: D J
authors.initials: DJ
authors.lastname: Lee
authors.forename: B M
authors.initials: BM
authors.lastname: Dale
authors.forename: J
authors.initials: J
authors.lastname: Calafat
authors.forename: S
authors.initials: S
authors.lastname: Greenberg
mesh_terms: D016475:3T3 Cells; D000483:Alleles; D000818:Animals; D001692:Biological Transport; D002451:Cell Compartmentation / Q000502:physiology*; D002460:Cell Line; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D051379:Mice; D016253:Microscopy, Immunoelectron; D010587:Phagocytosis / Q000502:physiology*; D017452:Receptors, IgG / Q000502:physiology; D011990:Receptors, Transferrin / Q000378:metabolism; D014168:Transferrin / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D000099193:rab11 GTP-Binding Proteins
chemical_list: D017452:Receptors, IgG; D011990:Receptors, Transferrin; D014168:Transferrin; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins