title: Receptor complexes cotransported via polarized endocytic pathways form clusters with distinct organizations.
abstract: Previously, FRET confocal microscopy has shown that polymeric IgA-receptor (pIgA-R) is distributed in a clustered manner in apical endosomes. To test whether different membrane-bound components form clusters during membrane trafficking, live-cell quantitative FRET was used to characterize the organization of pIgA-R and transferrin receptor (TFR) in endocytic membranes of polarized MDCK cells upon internalization of donor- and acceptor-labeled ligands. We show that pIgA-R and TFR complexes form increasingly organized clusters during cotransport from basolateral to perinuclear endosomes. The organization of these receptor clusters in basolateral versus perinuclear/apical endosomes is significantly different; the former showing a mixed random/clustered distribution while the latter highly organized clusters. Our results indicate that although both perinuclear and apical endosomes comprise pIgA-R and TFR clusters, their E% levels are significantly different suggesting that these receptors are packed into clusters in a distinct manner. The quantitative FRET-based assay presented here suggests that different receptor complexes form clusters, with diverse levels of organization, while being cotransported via the polarized endocytic pathways.
authors.affiliation: Department of Biology, W. M. Keck Center for Cellular Imaging, University of Virginia, Charlottesville, VA 22904, USA.
authors.forename: H
authors.initials: H
authors.lastname: Wallrabe
authors.forename: G
authors.initials: G
authors.lastname: Bonamy
authors.forename: A
authors.initials: A
authors.lastname: Periasamy
authors.forename: M
authors.initials: M
authors.lastname: Barroso
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D048430:Cell Shape; D004285:Dogs; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism / Q000648:ultrastructure; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D007070:Immunoglobulin A / Q000378:metabolism*; D008954:Models, Biological; D019056:Receptors, Polymeric Immunoglobulin / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D011990:Receptors, Transferrin / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D007070:Immunoglobulin A; D019056:Receptors, Polymeric Immunoglobulin; D011990:Receptors, Transferrin; C034639:polymeric IgA