SAS-4 Protein in Trypanosoma brucei Controls Life Cycle Transitions by Modulating the Length of the Flagellum Attachment Zone Filament.
The evolutionarily conserved centriole/basal body protein SAS-4 regulates centriole duplication in metazoa and basal body duplication in flagellated and ciliated organisms. Here, we report that the SAS-4 homolog in the flagellated protozoan Trypanosoma brucei, TbSAS-4, plays an unusual role in controlling life cycle transitions by regulating the length of the flagellum attachment zone (FAZ) filament, a specialized cytoskeletal structure required for flagellum adhesion and cell morphogenesis. TbSAS-4 is concentrated at the distal tip of the FAZ filament, and depletion of TbSAS-4 in the trypomastigote form disrupts the elongation of the new FAZ filament, generating cells with a shorter FAZ associated with a longer unattached flagellum and repositioned kinetoplast and basal body, reminiscent of epimastigote-like morphology. Further, we show that TbSAS-4 associates with six additional FAZ tip proteins, and depletion of TbSAS-4 disrupts the enrichment of these FAZ tip proteins at the new FAZ tip, suggesting a role of TbSAS-4 in maintaining the integrity of this FAZ tip protein complex. Together, these results uncover a novel function of TbSAS-4 in regulating the length of the FAZ filament to control basal body positioning and life cycle transitions in T. brucei.
From the Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, Texas 77030.
Huiqing
H
Hu
From the Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, Texas 77030.
Qing
Q
Zhou
From the Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, Texas 77030 Ziyin.Li@uth.tmc.edu.
Ziyin
Z
Li
D005407:Flagella / Q000235:genetics / Q000378:metabolism*; D008018:Life Cycle Stages / Q000502:physiology*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000254:growth & development*
D015800:Protozoan Proteins
RNA interference (RNAi); SAS-4; Trypanosoma brucei; basal body; cell biology; cell differentiation; centrosome; epimastigote; flagellum attachment zone; microbiology; microscopy; trypomastigote