Vesicles Bearing Toxoplasma Apicoplast Membrane Proteins Persist Following Loss of the Relict Plastid or Golgi Body Disruption

被引:15
|
作者
Bouchut, Anne [1 ]
Geiger, Jennifer A. [1 ,2 ]
DeRocher, Amy E. [1 ]
Parsons, Marilyn [1 ,2 ]
机构
[1] Seattle Biomed Res Inst, Seattle, WA 98109 USA
[2] Univ Washington, Dept Global Hlth, Seattle, WA 98195 USA
来源
PLOS ONE | 2014年 / 9卷 / 11期
基金
美国国家卫生研究院;
关键词
ENDOPLASMIC-RETICULUM; PLASMODIUM-FALCIPARUM; MOLECULAR CHARACTERIZATION; BINDING PROTEIN; LIPID DROPLETS; GONDII; TRAFFICKING; TRANSPORT; PATHWAY; CHLOROPLAST;
D O I
10.1371/journal.pone.0112096
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Toxoplasma gondii and malaria parasites contain a unique and essential relict plastid called the apicoplast. Most apicoplast proteins are encoded in the nucleus and are transported to the organelle via the endoplasmic reticulum (ER). Three trafficking routes have been proposed for apicoplast membrane proteins: (i) vesicular trafficking from the ER to the Golgi and then to the apicoplast, (ii) contiguity between the ER membrane and the apicoplast allowing direct flow of proteins, and (iii) vesicular transport directly from the ER to the apicoplast. Previously, we identified a set of membrane proteins of the T. gondii apicoplast which were also detected in large vesicles near the organelle. Data presented here show that the large vesicles bearing apicoplast membrane proteins are not the major carriers of luminal proteins. The vesicles continue to appear in parasites which have lost their plastid due to mis-segregation, indicating that the vesicles are not derived from the apicoplast. To test for a role of the Golgi body in vesicle formation, parasites were treated with brefeldin A or transiently transfected with a dominant-negative mutant of Sar1, a GTPase required for ER to Golgi trafficking. The immunofluorescence patterns showed little change. These findings were confirmed using stable transfectants, which expressed the toxic dominant-negative sar1 following Cre-loxP mediated promoter juxtaposition. Our data support the hypothesis that the large vesicles do not mediate the trafficking of luminal proteins to the apicoplast. The results further show that the large vesicles bearing apicoplast membrane proteins continue to be observed in the absence of Golgi and plastid function. These data raise the possibility that the apicoplast proteome is generated by two novel ER to plastid trafficking pathways, plus the small set of proteins encoded by the apicoplast genome.
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页数:14
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