title: Adaptor protein-3 (AP-3) complex mediates the biogenesis of acidocalcisomes and is essential for growth and virulence of Trypanosoma brucei.
abstract: Acidocalcisomes are acidic calcium and polyphosphate storage organelles found in a diverse range of organisms. Here we present evidence that the biogenesis of acidocalcisomes in Trypanosoma brucei is linked to the expression of adaptor protein-3 (AP-3) complex. Localization studies in cell lines expressing β3 and δ subunits of AP-3 fused to epitope tags revealed their partial co-localization with the vacuolar proton pyrophosphatase, a marker of acidocalcisomes, with the Golgi marker Golgi reassembly and stacking protein, and with antibodies against the small GTPase Rab11. Ablation of the β3 subunit by RNA interference (RNAi) resulted in disappearance of acidocalcisomes from both procyclic and bloodstream form trypanosomes, as revealed by immmunofluorescence and electron microscopy assays, with no alterations in trafficking of different markers to lysosomes. Knockdown of the β3 subunit resulted in lower acidic calcium, pyrophosphate, and polyphosphate content as well as defects in growth in culture, resistance to osmotic stress, and virulence in mice. Similar results were obtained by knocking down the expression of the δ subunit of AP-3. These results indicate that AP-3 is essential for the biogenesis of acidocalcisomes and for growth and virulence of T. brucei.
authors: Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia 30602, USA.
authors: Guozhong
authors: G
authors: Huang
authors: Jianmin
authors: J
authors: Fang
authors: Celso
authors: C
authors: Sant'Anna
authors: Zhu-Hong
authors: ZH
authors: Li
authors: Dianne L
authors: DL
authors: Wellems
authors: Peter
authors: P
authors: Rohloff
authors: Roberto
authors: R
authors: Docampo
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D051379:Mice; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D015388:Organelles / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
chemical_list: D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; D015800:Protozoan Proteins; D014157:Transcription Factors; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C060759:enhancer-binding protein AP-3