title: Mechanism of constitutive export from the golgi: bulk flow via the formation, protrusion, and en bloc cleavage of large trans-golgi network tubular domains.
abstract: Transport of constitutive cargo proteins from the Golgi complex to the plasma membrane (PM) is known to be mediated by large tubular-saccular carriers moving along microtubules. However, the process by which these large structures emerge from the trans-Golgi network (TGN) remains unclear. Here, we address the question of the formation of Golgi-to-PM carriers (GPCs) by using a suitable cluster of morphological techniques, providing an integrated view of their dynamics and three-dimensional structure. Our results indicate that exit from the TGN of a constitutive traffic marker, the VSVG protein, occurs by bulk flow and is a three-step process. First, the formation of a tubular-reticular TGN domain (GPC precursor) that includes PM-directed proteins and excludes other cargo and Golgi-resident proteins. Notably, this step does not require membrane fusion. Second, the docking of this preformed domain on microtubules and its kinesin-mediated extrusion. Finally, the detachment of the extruded domain by membrane fission. The formation of GPCs does not involve cargo concentration and is not associated with the presence of known coat proteins on GPC precursors. In summary, export from the Golgi occurs via the formation, protrusion and en bloc cleavage of specialized TGN tubular-saccular domains.
authors.affiliation: Department of Cell Biology and Oncology, Istituto di Ricerche Farmacologiche Mario Negri, 66030 Santa Maria Imbaro, Chieti, Italy. polish@negrisrud.it
authors.forename: Elena V
authors.initials: EV
authors.lastname: Polishchuk
authors.forename: Alessio
authors.initials: A
authors.lastname: Di Pentima
authors.forename: Alberto
authors.initials: A
authors.lastname: Luini
authors.forename: Roman S
authors.initials: RS
authors.lastname: Polishchuk
mesh_terms: D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D002462:Cell Membrane / Q000502:physiology* / Q000648:ultrastructure; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D002966:Clathrin / Q000378:metabolism / Q000502:physiology; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000502:physiology* / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000502:physiology* / Q000648:ultrastructure; D006367:HeLa Cells; D006801:Humans; D008561:Membrane Fusion / Q000502:physiology; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology; D008845:Microinjections; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D008870:Microtubules / Q000502:physiology* / Q000648:ultrastructure; D008958:Models, Molecular; D014759:Viral Envelope Proteins / Q000378:metabolism / Q000502:physiology; D021601:trans-Golgi Network / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D002966:Clathrin; C028391:G protein, vesicular stomatitis virus; D008562:Membrane Glycoproteins; D014759:Viral Envelope Proteins