title: Clathrin-independent carriers form a high capacity endocytic sorting system at the leading edge of migrating cells.
abstract: Although the importance of clathrin- and caveolin-independent endocytic pathways has recently emerged, key aspects of these routes remain unknown. Using quantitative ultrastructural approaches, we show that clathrin-independent carriers (CLICs) account for approximately three times the volume internalized by the clathrin-mediated endocytic pathway, forming the major pathway involved in uptake of fluid and bulk membrane in fibroblasts. Electron tomographic analysis of the 3D morphology of the earliest carriers shows that they are multidomain organelles that form a complex sorting station as they mature. Proteomic analysis provides direct links between CLICs, cellular adhesion turnover, and migration. Consistent with this, CLIC-mediated endocytosis of key cargo proteins, CD44 and Thy-1, is polarized at the leading edge of migrating fibroblasts, while transient ablation of CLICs impairs their ability to migrate. These studies provide the first quantitative ultrastructural analysis and molecular characterization of the major endocytic pathway in fibroblasts, a pathway that provides rapid membrane turnover at the leading edge of migrating cells.
authors: The Institute for Molecular Bioscience and Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors: Mark T
authors: MT
authors: Howes
authors: Matthew
authors: M
authors: Kirkham
authors: James
authors: J
authors: Riches
authors: Katia
authors: K
authors: Cortese
authors: Piers J
authors: PJ
authors: Walser
authors: Fiona
authors: F
authors: Simpson
authors: Michelle M
authors: MM
authors: Hill
authors: Alun
authors: A
authors: Jones
authors: Richard
authors: R
authors: Lundmark
authors: Margaret R
authors: MR
authors: Lindsay
authors: Delia J
authors: DJ
authors: Hernandez-Deviez
authors: Gordana
authors: G
authors: Hadzic
authors: Adam
authors: A
authors: McCluskey
authors: Rumasia
authors: R
authors: Bashir
authors: Libin
authors: L
authors: Liu
authors: Paul
authors: P
authors: Pilch
authors: Harvey
authors: H
authors: McMahon
authors: Phillip J
authors: PJ
authors: Robinson
authors: John F
authors: JF
authors: Hancock
authors: Satyajit
authors: S
authors: Mayor
authors: Robert G
authors: RG
authors: Parton
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000502:physiology; D015415:Biomarkers / Q000378:metabolism; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D002465:Cell Movement / Q000502:physiology*; D016764:Cell Polarity; D002966:Clathrin / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism* / Q000648:ultrastructure; D005347:Fibroblasts / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D018345:Mice, Knockout; D041681:NIH 3T3 Cells; D013347:Subcellular Fractions / Q000737:chemistry / Q000378:metabolism
chemical_list: D015415:Biomarkers; D051242:Caveolin 1; D002966:Clathrin