title: IL4/PGE2 induction of an enlarged early endosomal compartment in mouse macrophages is Rab5-dependent.
abstract: The endosomal compartment and the plasma membrane form a complex partnership that controls signal transduction and trafficking of different molecules. The specificity and functionality of the early endocytic pathway are regulated by a growing number of Rab GTPases, particularly Rab5. In this study, we demonstrate that IL4 (a Th-2 cytokine) and prostaglandin E2 (PGE2) synergistically induce Rab5 and several Rab effector proteins, including Rin1 and EEA1, and promote the formation of an enlarged early endocytic (EEE) compartment. Endosome enlargement is linked to a substantial induction of the mannose receptor (MR), a well-characterized macrophage endocytic receptor. Both MR levels and MR-mediated endocytosis are enhanced approximately 7-fold. Fluid-phase endocytosis is also elevated in treated cells. Light microscopy and fractionation studies reveal that MR colocalizes predominantly with Rab5a and partially with Rab11, an endosomal recycling pathway marker. Using retroviral expression of Rab5a:S34N, a dominant negative mutant, and siRNA Rab5a silencing, we demonstrate that Rab5a is essential for the large endosome phenotype and for localization of MR in these structures. We speculate that the EEE is maintained by activated Rab5, and that the EEE phenotype is part of some macrophage developmental program such as cell fusion, a characteristic of IL4-stimulated cells.
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, 660 S. Euclid, Campus Box 8228, Saint Louis, MO 63110, USA.
authors.forename: Marisa J
authors.initials: MJ
authors.lastname: Wainszelbaum
authors.forename: Brandon M
authors.initials: BM
authors.lastname: Proctor
authors.forename: Suzanne E
authors.initials: SE
authors.lastname: Pontow
authors.forename: Philip D
authors.initials: PD
authors.lastname: Stahl
authors.forename: M Alejandro
authors.initials: MA
authors.lastname: Barbieri
mesh_terms: D000818:Animals; D001324:Autoantigens / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D015232:Dinoprostone / Q000494:pharmacology*; D004357:Drug Synergism; D004705:Endocytosis / Q000187:drug effects; D011992:Endosomes / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure; D015847:Interleukin-4 / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D037181:Lectins, C-Type / Q000032:analysis / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D008297:Male; D008351:Mannans / Q000378:metabolism; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000032:analysis / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008854:Microscopy, Electron; D010873:Pinocytosis / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D011956:Receptors, Cell Surface / Q000032:analysis / Q000378:metabolism; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000032:analysis / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D000090802:rab7 GTP-Binding Proteins; D020703:ras GTPase-Activating Proteins / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
chemical_list: D001324:Autoantigens; D002352:Carrier Proteins; D015232:Dinoprostone; D015847:Interleukin-4; D047908:Intracellular Signaling Peptides and Proteins; D037181:Lectins, C-Type; D008351:Mannans; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins; D000090802:rab7 GTP-Binding Proteins; D020703:ras GTPase-Activating Proteins; D000099193:rab11 GTP-Binding Proteins; C101203:IQ motif containing GTPase activating protein 1; C490451:Rin1 protein, mouse; C093846:early endosome antigen 1