title: A novel hook-related protein family and the characterization of hook-related protein 1.
abstract: The spatial organization of organelles within a cell is dependent on microtubules. Recently, members of the Hook family of proteins have been proposed to function in linking organelles to microtubules. We report the identification of a completely novel protein family, the Hook-related protein (HkRP) family, from which the Hook proteins have diverged. Bioinformatic analysis of the HkRP family revealed several conserved domains, including a unique C-terminal HkRP domain. The central region of each protein is comprised of an extensive coiled-coil domain, and the N-terminus contains a putative microtubule-binding domain. This domain has been shown to bind microtubules in the Hook protein and show that the HkRP1 protein is microtubule-associated. While endogenous HkRP1 has no distinct organelle association, expression of the C-terminal membrane-binding domain suggests a function of the HkRP1 in early endosome. Ultrastructural studies reveal that expression of the C-terminal HkRP1 domain causes an accumulation of internal membranes with an electron-dense coat. Co-localization studies show a concomitant redistribution of the early endosome marker sorting-nexin 1 but not the early endosome antigen-1 (EEA1). The steady-state distribution of the epidermal growth factor receptor is also specifically disrupted by expression of the C-terminal domain. We propose that HkRP1 is involved in the process of tubulation of sorting nexin-1 positive membranes from early endosome subdomains.
authors.affiliation: Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD 4072, Australia. f.simpson@imb.uq.edu.au
authors.forename: Fiona
authors.initials: F
authors.lastname: Simpson
authors.forename: Sally
authors.initials: S
authors.lastname: Martin
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Evans
authors.forename: Markus
authors.initials: M
authors.lastname: Kerr
authors.forename: David E
authors.initials: DE
authors.lastname: James
authors.forename: Robert G
authors.initials: RG
authors.lastname: Parton
authors.forename: Rohan D
authors.initials: RD
authors.lastname: Teasdale
authors.forename: Carol
authors.initials: C
authors.lastname: Wicking
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D017173:Caenorhabditis elegans; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D019295:Computational Biology; D006224:Cricetinae; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D030541:Databases, Genetic; D004331:Drosophila melanogaster; D034281:Dynamins / Q000378:metabolism; D005091:Exons; D018507:Gene Expression Regulation, Developmental; D015723:Gene Library; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D017403:In Situ Hybridization; D008565:Membrane Proteins / Q000737:chemistry; D051379:Mice; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D008957:Models, Genetic; D008969:Molecular Sequence Data; D005810:Multigene Family; D017239:Paclitaxel / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D017422:Sequence Analysis, DNA; D014404:Tubulin / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; C471056:Hook1 protein, mouse; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D014404:Tubulin; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; D049452:Green Fluorescent Proteins; D034281:Dynamins; D017239:Paclitaxel