N-ethylmaleimide-sensitive factor is required to organize functional exocytotic microdomains in paramecium.
In exocytosis, secretory granules contact plasma membrane at sites where microdomains can be observed, which are sometimes marked by intramembranous particle arrays. Such arrays are particularly obvious when membrane fusion is frozen at a subterminal stage, e.g., in neuromuscular junctions and ciliate exocytotic sites. In Paramecium, a genetic approach has shown that the "rosettes" of intramembranous particles are essential for stimulated exocytosis of secretory granules, the trichocysts. The identification of two genes encoding the N-ethylmaleimide-sensitive factor (NSF), a chaperone ATPase involved in organelle docking, prompted us to analyze its potential role in trichocyst exocytosis using a gene-silencing strategy. Here we show that NSF deprivation strongly interferes with rosette assembly but does not disturb the functioning of exocytotic sites already formed. We conclude that rosette organization involves ubiquitous partners of the fusion machinery and discuss where NSF could intervene in this mechanism.
Froissard
Marine
M
Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, 91198 Gif-sur-Yvette Cedex, France.
Kissmehl
Roland
R
Dedieu
Jean-Claude
JC
Gulik-Krzywicki
Tadeusz
T
Plattner
Helmut
H
Cohen
Jean
J
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D005089:Exocytosis / Q000502:physiology*; D020868:Gene Silencing; D008561:Membrane Fusion / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D052066:N-Ethylmaleimide-Sensitive Proteins; D010247:Paramecium / Q000235:genetics*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D015800:Protozoan Proteins; D033921:Vesicular Transport Proteins; D052066:N-Ethylmaleimide-Sensitive Proteins