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Cholera toxin toxicity does not require functional Arf6- and dynamin-dependent endocytic pathways.
Ramiro H Massol1, Jakob E Larsen, Yukako Fujinaga
1Department of Cell Biology, Harvard Medical School and The Center for Blood Research for Biomedical Research, Boston, Massachusetts 02115, USA.
Molecular Biology of the Cell
|May 18, 2004
Summary
Cholera toxin (CT) uses multiple pathways to enter cells. Blocking major entry routes did not stop CT toxicity, suggesting an alternative pathway to the endoplasmic reticulum (ER).
Area of Science:
- Cell Biology
- Molecular Biology
- Toxicology
Background:
- Cholera toxin (CT) and AB(5) toxins target cell membranes.
- Retrograde transport to the Golgi and endoplasmic reticulum (ER) is crucial for CT toxicity.
- ER translocation of the catalytic subunit leads to cellular damage.
Purpose of the Study:
- Investigate the endocytic pathways utilized by Cholera toxin (CT).
- Determine the role of clathrin-, caveolin-, and Arf6-dependent pathways in CT retrograde transport.
- Identify the mechanism of CT entry into the ER and subsequent toxicity.
Main Methods:
- Fluorescence microscopy to track CT internalization.
- Overexpression of dominant mutants to inhibit specific endocytic pathways.
- Assessment of CT toxicity following pathway inhibition.
Main Results:
- CT is internalized via multiple endocytic routes.
- Inhibiting clathrin-, caveolin-, or Arf6-dependent pathways did not impede CT retrograde transport or toxicity.
- Blocking all three pathways simultaneously did not abolish CT-induced toxicity, despite reduced Golgi and ER presence.
Conclusions:
- The clathrin-, caveolin-, and Arf6-dependent pathways are not essential for CT retrograde transport to the ER.
- An alternative, unidentified pathway facilitates CT entry into the ER.
- CT toxicity can occur independently of these major endocytic routes.