The secretion inhibitor Exo2 perturbs trafficking of Shiga toxin between endosomes and the trans-Golgi network.
The small-molecule inhibitor Exo2 {4-hydroxy-3-methoxy-(5,6,7,8-tetrahydrol[1]benzothieno[2,3-d]pyrimidin-4-yl)hydraz-one benzaldehyde} has been reported to disrupt the Golgi apparatus completely and to stimulate Golgi-ER (endoplasmic reticulum) fusion in mammalian cells, akin to the well-characterized fungal toxin BFA (brefeldin A). It has also been reported that Exo2 does not affect the integrity of the TGN (trans-Golgi network), or the direct retrograde trafficking of the glycolipid-binding cholera toxin from the TGN to the ER lumen. We have examined the effects of BFA and Exo2, and found that both compounds are indistinguishable in their inhibition of anterograde transport and that both reagents significantly disrupt the morphology of the TGN in HeLa and in BS-C-1 cells. However, Exo2, unlike BFA, does not induce tubulation and merging of the TGN and endosomal compartments. Furthermore, and in contrast with its effects on cholera toxin, Exo2 significantly perturbs the delivery of Shiga toxin to the ER. Together, these results suggest that the likely target(s) of Exo2 operate at the level of the TGN, the Golgi and a subset of early endosomes, and thus Exo2 provides a more selective tool than BFA for examining membrane trafficking in mammalian cells.
Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.
Robert A
RA
Spooner
Peter
P
Watson
Daniel C
DC
Smith
Frédéric
F
Boal
Mohammed
M
Amessou
Ludger
L
Johannes
Guy J
GJ
Clarkson
J Michael
JM
Lord
David J
DJ
Stephens
Lynne M
LM
Roberts
D000818:Animals; D001547:Benzaldehydes / Q000378:metabolism / Q000494:pharmacology*; D020126:Brefeldin A / Q000494:pharmacology; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D021381:Protein Transport / Q000187:drug effects; D011743:Pyrimidines / Q000378:metabolism / Q000494:pharmacology*; D022621:Shiga Toxin / Q000378:metabolism*; D014709:Vero Cells; D021601:trans-Golgi Network / Q000187:drug effects / Q000378:metabolism*
C495416:4-hydroxy-3-methoxy-(5,6,7,8-tetrahydro(1)benzothieno(2,3-d)pyrimidin-4-yl)hydrazone benzaldehyde; D001547:Benzaldehydes; D011743:Pyrimidines; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D020126:Brefeldin A; D022621:Shiga Toxin