title: Human GCIP interacts with CT847, a novel Chlamydia trachomatis type III secretion substrate, and is degraded in a tissue-culture infection model.
abstract: The obligate intracellular bacterium Chlamydia trachomatis occupies a parasitophorous vacuole and employs a type III secretion mechanism to translocate host-interactive proteins. These proteins most likely contribute to pathogenesis through modulation of host cell mechanisms crucial for the establishment and maintenance of a permissive intracellular environment. Using a surrogate Yersinia type III secretion system (T3SS), we have identified the conserved gene product CT847 as a chlamydial T3SS substrate. Yeast two-hybrid studies using CT847 as bait to screen a HeLa cell cDNA library identified an interaction with mammalian Grap2 cyclin D-interacting protein (GCIP). Immunoblot analyses of C. trachomatis-infected HeLa cells showed that GCIP levels begin to decrease (as compared with mock-infected HeLa cells) between 8 h and 12 h post infection. GCIP was virtually undetectable in 24 h time point material. This decrease was inhibited by proteasome inhibitors lactacystin and MG-132, and the T3SS inhibitor Compound 1. CT847 was detectible in purified reticulate body but not elementary body lysates, and reverse transcription polymerase chain reaction (RT-PCR) expression analyses indicate a mid-cycle expression pattern. Both of these findings are consistent with CT847 contributing to the observed effect on GCIP. Given the established roles of GCIP, we believe that we have discovered a novel C. trachomatis antihost protein whose activity is relevant to chlamydial pathogenesis.
authors.affiliation: Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33101, USA.
authors.forename: Blandine
authors.initials: B
authors.lastname: Chellas-Géry
authors.forename: Camille N
authors.initials: CN
authors.lastname: Linton
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Fields
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism*; D002690:Chlamydia Infections / Q000378:metabolism* / Q000382:microbiology; D002692:Chlamydia trachomatis / Q000378:metabolism*; D015723:Gene Library; D006367:HeLa Cells; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011485:Protein Binding; D025941:Protein Interaction Mapping; D014157:Transcription Factors / Q000378:metabolism*; D015007:Yersinia / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C485815:CCNDBP1 protein, human; D007976:Leupeptins; D061988:Proteasome Inhibitors; D014157:Transcription Factors; C067713:lactacystin; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D000111:Acetylcysteine