title: Alpha-COPI coatomer protein is required for rough endoplasmic reticulum whorl formation in mosquito midgut epithelial cells.
abstract: BACKGROUND
  One of the early events in midgut epithelial cells of Aedes aegypti mosquitoes is the dynamic reorganization of rough endoplasmic reticulum (RER) whorl structures coincident with the onset of blood meal digestion. Based on our previous studies showing that feeding on an amino acid meal induces TOR signaling in Ae. aegypti, we used proteomics and RNAi to functionally identify midgut epithelial cell proteins that contribute to RER whorl formation.
  
  
  RESULTS
  Adult female Ae. aegypti mosquitoes were maintained on sugar alone (unfed), or fed an amino acid meal, and then midgut epithelial cells were analyzed by electron microscopy and protein biochemistry. The size and number of RER whorls in midgut epithelial cells were found to decrease significantly after feeding, and several KDEL-containing proteins were shown to have altered expression levels. LC-MS/MS mass spectrometry was used to analyze midgut microsomal proteins isolated from unfed and amino acid fed mosquitoes, and of the 127 proteins identified, 8 were chosen as candidate whorl forming proteins. Three candidate proteins were COPI coatomer subunits (alpha, beta, beta'), all of which appeared to be present at higher levels in microsomal fractions from unfed mosquitoes. Using RNAi to knockdown alpha-COPI expression, electron microscopy revealed that both the size and number of RER whorls were dramatically reduced in unfed mosquitoes, and moreover, that extended regions of swollen RER were prevalent in fed mosquitoes. Lastly, while a deficiency in alpha-COPI had no effect on early trypsin protein synthesis or secretion 3 hr post blood meal (PBM), expression of late phase proteases at 24 hr PBM was completely blocked.
  
  
  CONCLUSIONS
  alpha-COPI was found to be required for the formation of RER whorls in midgut epithelial cells of unfed Aa. aegypti mosquitoes, as well as for the expression of late phase midgut proteases.
authors.affiliation: Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona, United States of America.
authors.forename: Guoli
authors.initials: G
authors.lastname: Zhou
authors.forename: Jun
authors.initials: J
authors.lastname: Isoe
authors.forename: W Antony
authors.initials: WA
authors.lastname: Day
authors.forename: Roger L
authors.initials: RL
authors.lastname: Miesfeld
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002853:Chromatography, Liquid; D020756:Coatomer Protein / Q000235:genetics / Q000378:metabolism*; D004064:Digestive System / Q000166:cytology* / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D018870:Endoplasmic Reticulum, Rough / Q000378:metabolism* / Q000648:ultrastructure; D004847:Epithelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D005260:Female; D046529:Microscopy, Electron, Transmission; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053719:Tandem Mass Spectrometry
chemical_list: D020756:Coatomer Protein