Title

The cholera toxin A1(3) subdomain is essential for interaction with ADP-ribosylation factor 6 and full toxic activity but is not required for translocation from the endoplasmic reticulum to the cytosol

Authors

Authors

K. Teter; M. G. Jobling; D. Sentz;R. K. Holmes

Comments

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Abbreviated Journal Title

Infect. Immun.

Keywords

CHO-CELLS RESISTANT; C-TERMINAL REGION; HEAT-LABILE TOXIN; ESCHERICHIA-COLI; BREFELDIN-A; INTRACELLULAR TRAFFICKING; DEGRADATION; PATHWAY; RETRO-TRANSLOCATION; PLASMA-MEMBRANE; PROTEIN; Immunology; Infectious Diseases

Abstract

Cholera toxin (CT) moves from the plasma membrane to the endoplasmic reticulum (ER) by retrograde vesicular traffic. In the ER, the catalytic CTA1 polypeptide dissociates from the rest of the toxin and enters the cytosol by a process that involves the quality control mechanism of ER-associated degradation (ERAD). The cytosolic CTA1 then ADP ribosylates Gs alpha, resulting in adenylate cyclase activation and intoxication of the target cell. It is hypothesized that the C-terminal A1(3) subdomain of CTA1 plays two crucial roles in the. p intoxication process: (i) it contains a hydrophobic domain that triggers the ERAD mechanism and (ii) it facilitates interaction with the cytosolic ADP-ribosylation factors (ARFs) that serve as allosteric activators of CTA1 In this study, we examined the role(s) of the CTA1(3) subdomain in CT intoxication. Full-length CTA1 constructs and truncated CTA1 constructs lacking the A1(3), subdomain were generated and used to conduct two-hybrid studies of interactions with ARF6, in vitro enzyme assays, in vivo toxicity assays, and in vivo processing/degradation assays. Direct, plasm id-mediated expression of CTA1 constructs in the ER or cytosol of transfected CHO cells was used to perform the in vivo assays. With these methods, we found that the A1(3), subdomain of CTA1 is important both for interaction with ARF6 and for full expression of enzyme activity in vivo. Surprisingly, however, the A1(3), subdomain was not required for ERAD-mediated passage of CTA1 from the ER to the cytosol. A possible alternative trigger for CTA1 to activate the ERAD mechanism is discussed.

Journal Title

Infection and Immunity

Volume

74

Issue/Number

4

Publication Date

1-1-2006

Document Type

Article

Language

English

First Page

2259

Last Page

2267

WOS Identifier

WOS:000236477000029

ISSN

0019-9567

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