title: Ire1 supports normal ER differentiation in developing Drosophila photoreceptors.
abstract: The endoplasmic reticulum (ER) serves virtually all aspects of cell physiology and, by pathways that are incompletely understood, is dynamically remodeled to meet changing cell needs. Inositol-requiring enzyme 1 (Ire1), a conserved core protein of the unfolded protein response (UPR), participates in ER remodeling and is particularly required during the differentiation of cells devoted to intense secretory activity, so-called 'professional' secretory cells. Here, we characterize the role of Ire1 in ER differentiation in the developing Drosophila compound eye photoreceptors (R cells). As part of normal development, R cells take a turn as professional secretory cells with a massive secretory effort that builds the photosensitive membrane organelle, the rhabdomere. We find rough ER sheets proliferate as rhabdomere biogenesis culminates, and Ire1 is required for normal ER differentiation. Ire1 is active early in R cell development and is required in anticipation of peak biosynthesis. Without Ire1, the amount of rough ER sheets is strongly reduced and the extensive cortical ER network at the rhabdomere base, the subrhabdomere cisterna (SRC), fails. Instead, ER proliferates in persistent and ribosome-poor tubular tangles. A phase of Ire1 activity early in R cell development thus shapes dynamic ER.
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Zuyuan
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Madhusudana Rao
authors.initials: MR
authors.lastname: Chikka
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Hongai
authors.initials: H
authors.lastname: Xia
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA dready@purdue.edu.
authors.forename: Donald F
authors.initials: DF
authors.lastname: Ready
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D054910:Compound Eye, Arthropod / Q000166:cytology / Q000378:metabolism; D029721:Drosophila Proteins / Q000502:physiology*; D004331:Drosophila melanogaster / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000502:physiology* / Q000648:ultrastructure; D004722:Endoribonucleases / Q000502:physiology*; D005260:Female; D008297:Male; D009024:Morphogenesis; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D029721:Drosophila Proteins; D004722:Endoribonucleases; C511918:inositol requiring enzyme-1, Drosophila
keywords: Drosophila; ER; Ire1; Photoreceptor