title: Identification of conserved, centrosome-targeting ASH domains in TRAPPII complex subunits and TRAPPC8.
abstract: BACKGROUND
  Assembly of primary cilia relies on vesicular trafficking towards the cilium base and intraflagellar transport (IFT) between the base and distal tip of the cilium. Recent studies have identified several key regulators of these processes, including Rab GTPases such as Rab8 and Rab11, the Rab8 guanine nucleotide exchange factor Rabin8, and the transport protein particle (TRAPP) components TRAPPC3, -C9, and -C10, which physically interact with each other and function together with Bardet Biedl syndrome (BBS) proteins in ciliary membrane biogenesis. However, despite recent advances, the exact molecular mechanisms by which these proteins interact and target to the basal body to promote ciliogenesis are not fully understood.
  
  
  RESULTS
  We surveyed the human proteome for novel ASPM, SPD-2, Hydin (ASH) domain-containing proteins. We identified the TRAPP complex subunits TRAPPC8, -9, -10, -11, and -13 as novel ASH domain-containing proteins. In addition to a C-terminal ASH domain region, we predict that the N-terminus of TRAPPC8, -9, -10, and -11, as well as their yeast counterparts, consists of an α-solenoid bearing stretches of multiple tetratricopeptide (TPR) repeats. Immunofluorescence microscopy analysis of cultured mammalian cells revealed that exogenously expressed ASH domains, as well as endogenous TRAPPC8, localize to the centrosome/basal body. Further, depletion of TRAPPC8 impaired ciliogenesis and GFP-Rabin8 centrosome targeting.
  
  
  CONCLUSIONS
  Our results suggest that ASH domains confer targeting to the centrosome and cilia, and that TRAPPC8 has cilia-related functions. Further, we propose that the yeast TRAPPII complex and its mammalian counterpart are evolutionarily related to the bacterial periplasmic trafficking chaperone PapD of the usher pili assembly machinery.
authors.affiliation: Department of Biology, University of Copenhagen, Universitetsparken 13, Copenhagen, Denmark ; Center for Experimental Bioinformatics, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark.
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Schou
authors.affiliation: Department of Biology, University of Copenhagen, Universitetsparken 13, Copenhagen, Denmark.
authors.forename: Stine K
authors.initials: SK
authors.lastname: Morthorst
authors.affiliation: Department of Biology, University of Copenhagen, Universitetsparken 13, Copenhagen, Denmark.
authors.forename: Søren T
authors.initials: ST
authors.lastname: Christensen
authors.affiliation: Department of Biology, University of Copenhagen, Universitetsparken 13, Copenhagen, Denmark.
authors.forename: Lotte B
authors.initials: LB
authors.lastname: Pedersen
keywords: ASH domain; Centrosome; Cilia; Golgi; MSP domain; Rab8; Rabin8; TPR repeat; TRAPPII complex; Vesicle trafficking