Constitutive calcium-independent release of Toxoplasma gondii dense granules occurs through the NSF/SNAP/SNARE/Rab machinery.
The signals and the molecular machinery mediating release of dense matrix granules from pathogenic protozoan parasites are unknown. We compared the secretion of the endogenous dense granule marker GRA3 in Toxoplasma gondii with the release of a stably transfected foreign reporter, beta-lactamase, that localizes to parasite dense granules. Both proteins were released constitutively in a calcium-independent fashion, as shown using both intact and streptolysin O-permeabilized parasites. N-Ethylmaleimide and recombinant bovine Rab-guanine dissociation inhibitor inhibited beta-lactamase secretion in permeabilized parasites, whereas recombinant hamster N-ethylmaleimide-sensitive fusion protein and bovine alpha-SNAP augmented release. Guanosine 5'-3-O-(thio)triphosphate, but not cAMP, augmented secretion in the presence but not in the absence of ATP. The T. gondii NSF/SNAP/SNARE/Rab machinery participates in dense granule release using parasite protein components that can interact functionally with their mammalian homologues.
Chaturvedi
S
S
Departments of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Qi
H
H
Coleman
D
D
Rodriguez
A
A
Hanson
P I
PI
Striepen
B
B
Roos
D S
DS
Joiner
K A
KA
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002417:Cattle; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D005089:Exocytosis; D019204:GTP-Binding Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D052066:N-Ethylmaleimide-Sensitive Proteins; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000378:metabolism; D050600:SNARE Proteins; D013696:Temperature; D014122:Toxoplasma / Q000378:metabolism*; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D008565:Membrane Proteins; C110881:S-nitro-N-acetylpenicillamine; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D052066:N-Ethylmaleimide-Sensitive Proteins; D010396:Penicillamine; D002118:Calcium