Sea urchin egg preparations as systems for the study of calcium-triggered exocytosis.
This paper reviews recent work in our laboratory on the mechanism of calcium-triggered exocytosis. Upon echinoderm egg fertilization, cortical secretory vesicle exocytosis is massive and synchronous. By combining physiological and molecular analyses with a variety of purified membrane isolates containing secretory vesicles that fuse to the plasma membrane or each other, we have characterized the final steps of this calcium-triggered exocytosis. Our kinetic analysis led to a functional definition of the fusion complex whose activation by calcium follows Poisson statistics. The properties of this complex are compared with the properties of the heterotrimeric SNARE protein complex that is present in the cortical vesicle system. Our data do not support the hypothesis that this particular heterotrimeric complex is by itself the biological fusogen.
Zimmerberg
J
J
Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1855, USA. joshz@helix.nih.gov
Coorssen
J R
JR
Vogel
S S
SS
Blank
P S
PS
D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D005089:Exocytosis / Q000502:physiology*; D007700:Kinetics; D008565:Membrane Proteins / Q000502:physiology; D010063:Ovum / Q000502:physiology*; D050600:SNARE Proteins; D012617:Sea Urchins; D033921:Vesicular Transport Proteins
D008565:Membrane Proteins; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins