title: Essential role of the chaperonin CCT in rod outer segment biogenesis.
abstract: OBJECTIVE
  While some evidence suggests an essential role for the chaperonin containing t-complex protein 1 (CCT) in ciliogenesis, this function remains poorly understood mechanistically. We used transgenic mice, previously generated in our lab, and characterized by a genetically-induced suppression of CCT in rod photoreceptors as well as a malformation of the rod sensory cilia, the outer segments, to gain new insights into this underlying molecular mechanism.
  
  
  METHODS
  The CCT activity in rod photoreceptors of mice was suppressed by overexpressing the chaperonin inhibitor, phosducin-like protein short, and the ensuing changes of cellular morphology were analyzed by light and electron microscopy. Protein expression levels were studied by fluorescent microscopy and Western blotting.
  
  
  RESULTS
  Suppressing the chaperonin made the photoreceptors incompetent to build their outer segments. Specifically, the CCT-deficient rods appeared unable to expand the outer segment plasma membrane, and accommodate growth of this compartment. Seeking the molecular mechanisms underlying such a shortcoming, we found that the affected rods could not express normal levels of Bardet-Biedl Syndrome (BBS) proteins 2, 5, and 7 and, owing to that deficiency, were unable to assemble the BBSome, a multisubunit complex responsible for ciliary trafficking. A similar effect in response to the chaperonin suppression was also observed in cultured ciliated cells.
  
  
  CONCLUSIONS
  Our data provide new evidence indicating the essential role of the chaperonin CCT in the biogenesis of vertebrate photoreceptor sensory cilia, and suggest that it may be due to the direct participation of the chaperonin in the posttranslational processing of selected BBS proteins and assembly of the BBSome.
authors.affiliation: Department of Ophthalmology, West Virginia University, Morgantown, West Virginia, United States.
authors.forename: Satyabrata
authors.initials: S
authors.lastname: Sinha
authors.affiliation: Department of Ophthalmology, West Virginia University, Morgantown, West Virginia, United States.
authors.forename: Marycharmain
authors.initials: M
authors.lastname: Belcastro
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa, United States.
authors.forename: Poppy
authors.initials: P
authors.lastname: Datta
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa, United States.
authors.forename: Seongjin
authors.initials: S
authors.lastname: Seo
authors.affiliation: Department of Ophthalmology, West Virginia University, Morgantown, West Virginia, United States Department of Biochemistry, West Virginia University, Morgantown, West Virginia, United States.
authors.forename: Maxim
authors.initials: M
authors.lastname: Sokolov
mesh_terms: D000818:Animals; D020788:Bardet-Biedl Syndrome / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D015153:Blotting, Western; D002460:Cell Line; D056404:Chaperonin Containing TCP-1 / Q000096:biosynthesis / Q000235:genetics*; D004247:DNA / Q000235:genetics*; D004195:Disease Models, Animal; D004596:Electroretinography; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D008822:Mice, Transgenic; D012374:Rod Cell Outer Segment / Q000378:metabolism* / Q000473:pathology
chemical_list: D004247:DNA; D056404:Chaperonin Containing TCP-1
keywords: BBSome; Bardet-Biedl Syndrome; chaperonin CCT; outer segments; rods