title: Insect stage-specific receptor adenylate cyclases are localized to distinct subdomains of the Trypanosoma brucei Flagellar membrane.
abstract: Increasing evidence indicates that the Trypanosoma brucei flagellum (synonymous with cilium) plays important roles in host-parasite interactions. Several studies have identified virulence factors and signaling proteins in the flagellar membrane of bloodstream-stage T. brucei, but less is known about flagellar membrane proteins in procyclic, insect-stage parasites. Here we report on the identification of several receptor-type flagellar adenylate cyclases (ACs) that are specifically upregulated in procyclic T. brucei parasites. Identification of insect stage-specific ACs is novel, as previously studied ACs were constitutively expressed or confined to bloodstream-stage parasites. We show that procyclic stage-specific ACs are glycosylated, surface-exposed proteins that dimerize and possess catalytic activity. We used gene-specific tags to examine the distribution of individual AC isoforms. All ACs examined localized to the flagellum. Notably, however, while some ACs were distributed along the length of the flagellum, others specifically localized to the flagellum tip. These are the first transmembrane domain proteins to be localized specifically at the flagellum tip in T. brucei, emphasizing that the flagellum membrane is organized into specific subdomains. Deletion analysis reveals that C-terminal sequences are critical for targeting ACs to the flagellum, and sequence comparisons suggest that differential subflagellar localization might be specified by isoform-specific C termini. Our combined results suggest insect stage-specific roles for a subset of flagellar adenylate cyclases and support a microdomain model for flagellar cyclic AMP (cAMP) signaling in T. brucei. In this model, cAMP production is compartmentalized through differential localization of individual ACs, thereby allowing diverse cellular responses to be controlled by a common signaling molecule.
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California, USA.
authors.forename: Edwin A
authors.initials: EA
authors.lastname: Saada
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California, USA.
authors.forename: Z Pius
authors.initials: ZP
authors.lastname: Kabututu
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California, USA.
authors.forename: Miguel
authors.initials: M
authors.lastname: Lopez
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California, USA.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Shimogawa
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California, USA.
authors.forename: Gerasimos
authors.initials: G
authors.lastname: Langousis
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Oberholzer
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California, USA.
authors.forename: Angelica
authors.initials: A
authors.lastname: Riestra
authors.affiliation: Department of Biological Chemistry, University of California, Los Angeles, California, USA.
authors.forename: Zophonias O
authors.initials: ZO
authors.lastname: Jonsson
authors.affiliation: Department of Biological Chemistry, University of California, Los Angeles, California, USA Molecular Biology Institute, University of California, Los Angeles, California, USA.
authors.forename: James A
authors.initials: JA
authors.lastname: Wohlschlegel
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California, USA Molecular Biology Institute, University of California, Los Angeles, California, USA kenthill@mednet.ucla.edu.
authors.forename: Kent L
authors.initials: KL
authors.lastname: Hill
mesh_terms: D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D005407:Flagella / Q000201:enzymology*; D007313:Insecta / Q000469:parasitology; D008018:Life Cycle Stages; D021381:Protein Transport; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000254:growth & development
chemical_list: D015800:Protozoan Proteins; D012333:RNA, Messenger; D000262:Adenylyl Cyclases