title: Dynamics of transitional endoplasmic reticulum sites in vertebrate cells.
abstract: A typical vertebrate cell contains several hundred sites of transitional ER (tER). Presumably, tER sites generate elements of the ER-Golgi intermediate compartment (ERGIC), and ERGIC elements then generate Golgi cisternae. Therefore, characterizing the mechanisms that influence tER distribution may shed light on the dynamic behavior of the Golgi. We explored the properties of tER sites using Sec13 as a marker protein. Fluorescence microscopy confirmed that tER sites are long-lived ER subdomains. tER sites proliferate during interphase but lose Sec13 during mitosis. Unlike ERGIC elements, tER sites move very little. Nevertheless, when microtubules are depolymerized with nocodazole, tER sites redistribute rapidly to form clusters next to Golgi structures. Hence, tER sites have the unusual property of being immobile, yet dynamic. These findings can be explained by a model in which new tER sites are created by retrograde membrane traffic from the Golgi. We propose that the tER-Golgi system is organized by mutual feedback between these two compartments.
authors.affiliation: Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA.
authors.forename: A T
authors.initials: AT
authors.lastname: Hammond
authors.forename: B S
authors.initials: BS
authors.lastname: Glick
mesh_terms: D000818:Animals; D016466:CHO Cells; D002453:Cell Cycle; D002455:Cell Division; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure*; D005246:Feedback; D006056:Golgi Apparatus / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure*; D000077614:Golgi Matrix Proteins; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D008164:Luminescent Proteins / Q000032:analysis; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D008870:Microtubules / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D015739:Nocodazole / Q000494:pharmacology; D028861:Nuclear Pore Complex Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D014162:Transfection; D014714:Vertebrates; D014982:Xenopus laevis
chemical_list: D000077614:Golgi Matrix Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D028861:Nuclear Pore Complex Proteins; D011993:Recombinant Fusion Proteins; C079620:SEC13 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C087574:macrogolgin; D049452:Green Fluorescent Proteins; D015739:Nocodazole