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Protein toxins in membrane trafficking.

Abujarour, Ramzey J.

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Protein toxins in membrane trafficking.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Protein toxins in membrane trafficking./
作者:	Abujarour, Ramzey J.
面頁冊數:	118 p.
附註:	Source: Dissertation Abstracts International, Volume: 66-02, Section: B, page: 0653.
Contained By:	Dissertation Abstracts International66-02B.
標題:	Biology, Cell. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3163234
ISBN:	9780496971046

Protein toxins in membrane trafficking.
Abujarour, Ramzey J.

Protein toxins in membrane trafficking. - 118 p.

Source: Dissertation Abstracts International, Volume: 66-02, Section: B, page: 0653.

Thesis (Ph.D.)--The University of Texas at Dallas, 2005.

Members of the AB type of protein toxins intoxicate mammalian cells by targeting cellular proteins in the cytoplasm of their host cells. Some toxins such as shiga toxin (STX), exotoxin A (ETA), and ricin, are transported to the trans Golgi network (TGN) and the endoplasmic reticulum (ER) before their translocation into the cytoplasm. Transport of these toxins to the TGN and the ER is required to induce cellular intoxication. The rate of intoxication therefore reflects the ability of the toxin to reach the target sub-cellular compartment.

ISBN: 9780496971046Subjects--Topical Terms:

1017686
Biology, Cell.

Protein toxins in membrane trafficking.
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500 $a Supervisor: Rockford K. Draper.
502 $a Thesis (Ph.D.)--The University of Texas at Dallas, 2005.
520 $a Members of the AB type of protein toxins intoxicate mammalian cells by targeting cellular proteins in the cytoplasm of their host cells. Some toxins such as shiga toxin (STX), exotoxin A (ETA), and ricin, are transported to the trans Golgi network (TGN) and the endoplasmic reticulum (ER) before their translocation into the cytoplasm. Transport of these toxins to the TGN and the ER is required to induce cellular intoxication. The rate of intoxication therefore reflects the ability of the toxin to reach the target sub-cellular compartment.
520 $a In one study described in this thesis, I used the technique of RNA interference (RNAi) to investigate the involvement of Rab11, a small ras-like GTPase, in membrane trafficking of STX and ricin. Two ubiquitous Rab11 isoforms are expressed in mammalian cells (Rab11a and Rab11b), and localized mainly to the early/recycling endosome. Suppressing either Rab11a or Rab11b alone by RNAi had no effect on the cytotoxicity of STX. However, the double knockdown of the Rab11a and Rab11b sensitized HeLa cells to intoxication by STX, but not by ricin. The sensitizing effect was coupled to increased association of STX with endosomes and with increased transport to the TGN. These results suggest that Rab11a and Rab11b are involved in recycling of STX to the plasma membrane (PM). In addition, Rab6a and Rab6c have been implicated in the transport of STX to the TGN. To test our technical approach, I thus suppressed the two Rab proteins by RNAi and examined the effects on STX cytotoxicity and trafficking. As expected, the double knockdown of Rab6a and Rab6c protected HeLa cells against STX by inhibiting its transport to the TGN. Overall, the results implicate Rab11 in the regulation of STX recycling to the PM.
520 $a The rest of this theses focuses on my studies of how ER-targeted toxins translocate from the lumen of the ER into the cytoplasm. The process of retro-translocation is still vague, but it may involve the endoplasmic reticulum associated degradation (ERAD) pathway. The AAA ATPase p97 participates in the retro-translocation of cellular ERAD substrates and is therefore a candidate to participate in the retro-translocation of protein toxins. To investigate whether p97 functions in toxin retro-translocation to the cytoplasm, we measured the sensitivity to ER-targeted toxins of cells expressing either wild-type p97 or a dominant ATPase-defective p97 mutant under control of a tetracycline-inducible promoter. The rate at which cholera toxin and related toxins entered the cytoplasm was reduced in cells expressing the ATPase-defective p97, suggesting that the toxins might interact with p97. Overexpressing mutant p97 had no effect on the cytotoxicity of diphtheria toxin (DT), which translocates into cytoplasm from early endosomes and thus is not expected to interact with p97. To assess interaction, the cholera toxin A chain was immunoprecipitated from cholera toxin-treated Vero cells expressing p97. The immunoprecipitates contained both cholera toxin A chain (CTA) and p97, evidence that the two proteins are in a complex. Furthermore, similar experiments revealed that CTA co-immunoprecipitates with endogenous p97 as well. Altogether, these results provide functional and structural evidence that p97 participates in the transport of cholera toxin to the cytoplasm.
590 $a School code: 0382.
650 4 $a Biology, Cell. $3 1017686
650 4 $a Biology, Microbiology. $3 1017734
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