title: The Aspergillus nidulans peripheral ER: disorganization by ER stress and persistence during mitosis.
abstract: The genetically amenable fungus Aspergillus nidulans is well suited for cell biology studies involving the secretory pathway and its relationship with hyphal tip growth by apical extension. We exploited live-cell epifluorescence microscopy of the ER labeled with the translocon component Sec63, endogenously tagged with GFP, to study the organization of 'secretory' ER domains. The Sec63 A. nidulans ER network includes brightly fluorescent peripheral strands and more faintly labeled nuclear envelopes. In hyphae, the most abundant peripheral ER structures correspond to plasma membrane-associated strands that are polarized, but do not invade the hyphal tip dome, at least in part because the subapical collar of endocytic actin patches constrict the cortical strands in this region. Thus the subapical endocytic ring might provide an attachment for ER strands, thereby ensuring that the growing tip remains 'loaded' with secretory ER. Acute disruption of secretory ER function by reductive stress-mediated induction of the unfolded protein response results in the reversible aggregation of ER strands, cessation of exocytosis and swelling of the hyphal tips. The secretory ER is insensitive to brefeldin A treatment and does not undergo changes during mitosis, in agreement with the reports that apical extension continues at normal rates during this period.
authors.affiliation: Departamento de Biología Celular y Molecular, Centro de Investigaciones Biológicas Consejo Superior de Investigaciones Científicas, Madrid, Spain.
authors.forename: Ane
authors.initials: A
authors.lastname: Markina-Iñarrairaegui
authors.forename: Areti
authors.initials: A
authors.lastname: Pantazopoulou
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Espeso
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Peñalva
mesh_terms: D000199:Actins / Q000378:metabolism; D001233:Aspergillus nidulans / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D005089:Exocytosis / Q000187:drug effects; D005656:Fungal Proteins / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D025301:Hyphae / Q000187:drug effects / Q000378:metabolism; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D008938:Mitosis / Q000187:drug effects; D058105:Polymerization / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013172:Spores, Fungal / Q000187:drug effects / Q000378:metabolism; D056811:Unfolded Protein Response / Q000187:drug effects
chemical_list: D000199:Actins; D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D020126:Brefeldin A; D004229:Dithiothreitol