Flashcards in B2.081 Bacterial Toxins and Dehydration Deck (23)
what are the 4 classes of bacterial toxins?
1. surface acting
-hydrolysis of membrane lipids
-formation of pores
4. injected toxins
what is the heat labile (LT) mechanism?
specific to intestinal epithelial cells
hijacks internal cell signaling mechanism to activate CFTR
increases excretion of chloride ions
what is the heat stable (ST) mechanism?
surface acting toxin
specific for intestinal epithelial cells
binds cell surface signaling molecules
increases diverse ion pump functions
what provides the stability in ST toxins?
2 disulfide bonds
what is the mechanism of the shiga toxin?
causes cessation of RNA translation and protein synthesis
activates platelet aggregation (HUS)
what happens in the endosome after the engulfment of a toxin?
acidified by proton pump
drop in pH triggers conformational change in a subunit
what is the mechanism of diphtheria toxin?
binds to membrane bound receptors and enters via receptor-mediated endocytosis
after acidification, A domain is inserted into cytosol
A collects and inhibits protein synthesis by ribosylating EF-2
what are the hallmarks of anthrax?
lymph node swelling
what is the anthrax mechanism?
PA protein forms pore in membrane
LF and EF brought into cell via endosome
lowered pH triggers conformational change
pore allows lethal proteins access to cytosol
how can you tell if you ingested a preformed toxin?
symptoms arise in less than 3 hours
what is the duration of diarrhea when only the toxin was ingested?
shorter than usual
what type of protein is the botulism toxin (BoNT)?
interacts with GD1a (ganglioside) and Syt II/SV2
what differs in the receptors for BoNT and TeNT?
only one sugar unit on the sphingosine derived phospholipid
changes import mechanism
how do the effects of BoNT and TeNT differ?
BoNT blocks acetylcholine release of the PNS
TeNT is retoaxonally transported to intraneurons of the CNS
what is the mechanism of the C.diff toxin?
A disrupts ion pump
B damages actin
what is pseudomembrane colitis?
bacterial aggregation on colonic mucosa
what is the result of the C.diff toxin?
loss of membrane integrity
loss of fluid control
what is the result of pseudomembrane colitis?
inflammatory reaction that causes necrosis of the mucosal layer and decreased fluid absorption
what toxin is associated with campylobacter jejuni?
cytolethal distending toxin
what is the mechanism of the cytolethal distending toxin?
arrests cell cycle at G2/M phase
results in mucosal cell destruction and inflammatory necrosis (bloody) with loss of fluid control
what is the benefit of using a T3SS?
injection of toxins directly into cells through a pore
bypasses barrier mechanisms or need for membrane transporters
what channels transport water?