Retrograde transport of protein toxins under conditions of COPI dysfunction

Chen, Alice; Hu, Tonghuan; Mikoryak, Carole; Draper, Rockford K.

doi:10.1016/s0167-4889(02)00163-5

Cited by 33 publications

(23 citation statements)

References 46 publications

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“…The effect of simultaneous inhibition of COPI and Rab6A on the action of ricin and cholera toxin We recently noted that ldlF cells, a strain of CHO cells that carries a temperature-sensitive mutation in the ε subunit of COPI, were sensitive to ricin at the restrictive temperature (Chen et al, 2002). This suggested that ricin reaches the cytoplasm by a pathway that does not require ε-COP, such as the Rab6A-dependent pathway used by Shiga toxin.…”

Section: Resultsmentioning

confidence: 99%

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Evidence that the transport of ricin to the cytoplasm is independent of both Rab6A and COPI

Chen

AbuJarour

Draper

2003

Journal of Cell Science

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IntroductionCholera toxin, Shiga toxin and ricin are protein toxins that damage mammalian cells by a mechanism that includes four essential events: receptor-mediated endocytosis, retrograde transport into the lumen of the endoplasmic reticulum (ER), passage through the ER membrane into the cytoplasm, and catalytic inactivation of a target substrate in the cytoplasm. The receptor-binding site of a protein toxin is usually within a subunit or domain that is distinct from the subunit or domain that bears the catalytic activity of the toxin. Both cholera toxin and Shiga toxin belong to the AB5 protein toxin family in which the A chain is the enzymatic subunit and each of the five identical B chains bind cell surface receptors. The receptor for cholera toxin is the ganglioside GM1 and the receptor for Shiga toxin is the globotriaosyl ceramide G b3 (Lingwood, 1996;Spangler, 1992). The A chain of cholera toxin ADP-ribosylates a regulatory G protein and activates adenylate cyclase, which elevates the intracellular cAMP level (Spangler, 1992), whereas the A chain of Shiga toxin arrests protein synthesis by inactivating 28S ribosomal RNA . Ricin has a subunit organization different from the AB5 toxins and contains a single A chain and a single B chain. The B chain binds glycoconjugates that contain galactose residues so that either cell surface glycoproteins or glycolipids that contain galactose can serve as ricin receptors (Sandvig and van Deurs, 2000). The A chain of ricin arrests protein synthesis in target cells by inactivating 28S ribosomal RNA through an enzymatic mechanism identical to that of Shiga toxin .After binding to cell surface receptors, cholera toxin, Shiga toxin and ricin are endocytosed into vesicles and use pathways of retrograde transport to reach the lumen of the ER (Lencer et al., 1999;Lord and Roberts, 1998;Majoul et al., 1996;Rapak et al., 1997;Sandvig et al., 2002). Once in the ER, there is evidence that the catalytic chains of the toxins pass into the cytoplasm by reverse transport through the Sec61p translocon, the same protein complex used by secretory and membrane proteins to enter the ER from the cytoplasm (Koopmann et al., 2000;Schmitz et al., 2000;Simpson et al., 1999;Wesche et al., 1999). Protein toxins that exploit pathways of retrograde transport from the plasma membrane to the ER have been used as model systems to characterize the transport pathways. The best understood pathway of retrograde transport involves coat protein I (COPI), a large protein complex that is primarily found on vesicles budding from Golgi membranes (Cosson and Letourneur, 1997;Lippincott-Schwartz et al., 1998;Rothman and Wieland, 1996). The major component of COPI is coatomer, a cytoplasmic protein complex that contains seven subunits (α-, β-, β′-, γ-, δ-, ε-and ζ-COP) (Scales et al., 2000). Recruitment of COPI onto membranes depends on the activity of ADP ribosylation factor 1 (ARF1), a small GTPase protein, and its effectors (Aoe et al., 1997;Aoe et al., 1998). Together, coatomer and ARF1 constitute COPI. One fu...

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Section: Resultsmentioning

confidence: 99%

“…Coverslips were mounted and viewed with a Nikon TE300 microscope equipped with epi-illuminated fluorescence and a 60X lens (NA=1.4) as previously described (Chen et al, 2002). Images were obtained with a MicroMax digital camera (Princeton Instruments, Trenton, NJ, USA).…”

Section: Immunofluorescence Microscopymentioning

confidence: 99%

Evidence that the transport of ricin to the cytoplasm is independent of both Rab6A and COPI

Chen

AbuJarour

Draper

2003

Journal of Cell Science

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“…However, B subunits lacking an ER retention signal are also transported to the ER via an unknown mechanism. In addition, dysfunction of vesicles coated with COPI, which are involved in the retrograde transport of ER proteins containing a C-terminal KDEL motif, does not impair the entry of toxins such as CT (Chen et al, 2002). Thereby, CT, as well as ST, seems to use a KDEL-receptor-and COPI-independent pathway to gain access to the ER.…”

Section: Lipid-derivative Receptors and Long Trafficking Pathways Of mentioning

confidence: 99%

Bacterial protein toxins and lipids: role in toxin targeting and activity

Geny

Popoff

2006

Biology of the Cell

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All bacterial toxins, which globally are hydrophilic proteins, interact first with their target cells by recognizing a surface receptor, which is either a lipid or a lipid derivative, or another compound but in a lipid environment. Intracellular active toxins follow various trafficking pathways, the sorting of which is greatly dependent on the nature of the receptor, notably lipidic receptor or receptor embedded into a distinct environment such as lipid microdomains. Numerous other toxins act locally on cell membrane. Indeed, phospholipase activity is a common mechanism shared by several membrane‐damaging toxins. In addition, many toxins active intracellularly or on cell membrane modulate host cell phospholipid pathways. Unusually, a few bacterial toxins require a lipid post‐translational modification to be active. Thereby, lipids are obligate partners of bacterial toxins.

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“…Some toxins such as Shiga and Shiga-like toxins also seem to access the ER directly from the trans-Golgi because ER entry is insensitive to perturbations of COPI, required for retrograde transport through the Golgi stack and from the cis-part of the Golgi to the ER (Girod et al, 1999). Indeed, under conditions where most of the Golgi apparatus has been removed (e.g., upon addition of brefeldin-A treatment or by using the COPI-deficient Chinese hamster ovary cell-line LdlF), toxins still enter the ER, bypassing the Golgi stack (Chen et al, 2002;Llorente et al, 2003, Feng et al, 2004. These different lines of evidence are all suggestive of a direct route from the trans-Golgi to the ER that is independent of the Golgi stack.…”

Section: Rab6mentioning

confidence: 99%

Regulation of Microtubule-dependent Recycling at theTrans-Golgi Network by Rab6A and Rab6A'

Young

Stauber

Nery

et al. 2005

MBoC

104

126

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The small GTPase rab6A but not the isoform rab6A has previously been identified as a regulator of the COPIindependent recycling route that carries Golgi-resident proteins and certain toxins from the Golgi to the endoplasmic reticulum (ER). The isoform rab6A has been implicated in Golgi-to-endosomal recycling. Because rab6A but not A , binds rabkinesin6, this motor protein is proposed to mediate COPI-independent recycling. We show here that both rab6A and rab6A GTP-restricted mutants promote, with similar efficiency, a microtubule-dependent recycling of Golgi resident glycosylation enzymes upon overexpression. Moreover, we used small interfering RNA mediated down-regulation of rab6A and A' expression and found that reduced levels of rab6 perturbs organization of the Golgi apparatus and delays Golgi-to-ER recycling. Rab6-directed Golgi-to-ER recycling seems to require functional dynactin, as overexpression of p50/dynamitin, or a C-terminal fragment of Bicaudal-D, both known to interact with dynactin inhibit recycling. We further present evidence that rab6-mediated recycling seems to be initiated from the trans-Golgi network. Together, this suggests that a recycling pathway operates at the level of the trans-Golgi linking directly to the ER. This pathway would be the preferred route for both toxins and resident Golgi proteins. INTRODUCTIONAnterograde flow of material through the exocytic pathway is offset by the constant recycling of both proteins and lipids. This recycling helps to ensure that steady-state distributions of resident proteins are maintained within the pathway at the same time as keeping a lipid balance. Besides intra-Golgi recycling between cisternae (Hoe et al., 1995;Love et al., 1998;Lanoix et al., 1999;Lin et al., 1999), Golgi glycosylation enzymes also can recycle directly to the endoplasmic reticulum (ER). It is estimated that at least 5% of Golgi resident enzymes reside in the ER, at steady state (Pelletier et al., 2000). This pool constitutes recycled material originating from the Golgi apparatus (Cole et al., 1998;Storrie et al., 1998).The extent of ER recycling of Golgi resident membrane proteins is sufficient to allow for complete assembly of functional Golgi stacks. Thus, upon addition of nocodazole to depolymerize microtubules, the central and juxtanuclear Golgi apparatus relocates to the 100 or so peripheral ER exit sites scattered throughout the cell. This microtubule-independent relocation occurs in the absence of any detectable elements tracking outwards from the central Golgi apparatus. Rather, the Golgi apparatus undergoes a molecular deconstruction in the trans-to-cis-direction, i.e., resident glycosylation enzymes of the trans-cisternae/trans-Golgi network (TGN) relocate with faster kinetics than do enzymes of the medial-cisternae (Yang and Storrie, 1998). Enzymes seemingly enter the ER close to the microtubule organizing center (MTOC), diffuse through the ER, and then reemerge at peripheral ER exit sites. Here, Golgi stacks are then reassembled into discrete, yet fully functiona...

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Retrograde transport of protein toxins under conditions of COPI dysfunction

Cited by 33 publications

References 46 publications

Evidence that the transport of ricin to the cytoplasm is independent of both Rab6A and COPI

Evidence that the transport of ricin to the cytoplasm is independent of both Rab6A and COPI

Bacterial protein toxins and lipids: role in toxin targeting and activity

Regulation of Microtubule-dependent Recycling at theTrans-Golgi Network by Rab6A and Rab6A'

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