Abstract
Cholera toxin (CT) and related AB(5) toxins bind to glycolipids at the plasma membrane and are then transported in a retrograde manner, first to the Golgi and then to the endoplasmic reticulum (ER). In the ER, the catalytic subunit of CT is translocated into the cytosol, resulting in toxicity. Using fluorescence microscopy, we found that CT is internalized by multiple endocytic pathways. Inhibition of the clathrin-, caveolin-, or Arf6-dependent pathways by overexpression of appropriate dominant mutants had no effect on retrograde traffic of CT to the Golgi and ER, and it did not affect CT toxicity. Unexpectedly, when we blocked all three endocytic pathways at once, although fluorescent CT in the Golgi and ER became undetectable, CT-induced toxicity was largely unaffected. These results are consistent with the existence of an additional retrograde pathway used by CT to reach the ER.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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ADP-Ribosylation Factor 6
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ADP-Ribosylation Factors / analysis
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ADP-Ribosylation Factors / physiology*
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Animals
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Biological Assay
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Caveolin 1
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Caveolins / physiology
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Cell Line
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Cholera Toxin / analysis
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Cholera Toxin / metabolism*
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Cholera Toxin / toxicity*
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Clathrin / physiology
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Cytoplasmic Vesicles / chemistry
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Cytoplasmic Vesicles / immunology
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Cytoplasmic Vesicles / physiology
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Dynamins / physiology*
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Endocytosis / physiology*
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Endoplasmic Reticulum / chemistry
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Endoplasmic Reticulum / immunology
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Endoplasmic Reticulum / physiology
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Golgi Apparatus / chemistry
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Golgi Apparatus / immunology
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Golgi Apparatus / physiology
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Membrane Proteins / analysis
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Membrane Proteins / metabolism
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Protein Serine-Threonine Kinases / analysis
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Protein Serine-Threonine Kinases / metabolism
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Protein Transport / physiology
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Vesicular Transport Proteins
Substances
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ADP-Ribosylation Factor 6
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Caveolin 1
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Caveolins
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Clathrin
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Membrane Proteins
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Vesicular Transport Proteins
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early endosome antigen 1
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Cholera Toxin
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AAK1 protein, human
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Protein Serine-Threonine Kinases
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ADP-Ribosylation Factors
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ARF6 protein, human
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Dynamins