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J. Cell Biol.,
Volume 140, Number 3, February 9, 1998 525-540

* Department of Biochemistry, University of Geneva, 1211 Geneva, Switzerland; In this paper, we have investigated the effects of the pore-forming toxin aerolysin, produced by
Aeromonas hydrophila, on mammalian cells. Our data
indicate that the protoxin binds to an 80-kD glycosyl-phosphatidylinositol (GPI)-anchored protein on BHK
cells, and that the bound toxin is associated with specialized plasma membrane domains, described as detergent-insoluble microdomains, or cholesterol-glycolipid
"rafts." We show that the protoxin is then processed to
its mature form by host cell proteases. We propose that
the preferential association of the toxin with rafts,
through binding to GPI-anchored proteins, is likely to
increase the local toxin concentration and thereby promote oligomerization, a step that it is a prerequisite for
channel formation. We show that channel formation
does not lead to disruption of the plasma membrane but to the selective permeabilization to small ions such
as potassium, which causes plasma membrane depolarization. Next we studied the consequences of channel
formation on the organization and dynamics of intracellular membranes. Strikingly, we found that the toxin causes dramatic vacuolation of the ER, but does not affect other intracellular compartments. Concomitantly
we find that the COPI coat is released from biosynthetic membranes and that biosynthetic transport of
newly synthesized transmembrane G protein of vesicular stomatitis virus is inhibited. Our data indicate that
binding of proaerolysin to GPI-anchored proteins and
processing of the toxin lead to oligomerization and
channel formation in the plasma membrane, which in
turn causes selective disorganization of early biosynthetic membrane dynamics.
Center for Microscopy and Microanalysis,
Department of Physiology and Pharmacology, and Center for Molecular and Cellular Biology, University of Queensland,
Queensland 4072, Brisbane, Australia
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