IHEM 20887
INSTITUTO DE HISTOLOGIA Y EMBRIOLOGIA DE MENDOZA DR. MARIO H. BURGOS
Unidad Ejecutora - UE
artículos
Título:
Acrosomal swelling and membrane docking are required for hybrid vesicle formation during the human sperm acrosome reaction
Autor/es:
ZANETTI, MN; MAYORGA, LS
Revista:
BIOLOGY OF REPRODUCTION
Editorial:
SOC STUDY REPRODUCTION
Referencias:
Año: 2009 vol. 81 p. 396 - 405
ISSN:
0006-3363
Resumen:
Acrosomal exocytosis in mammalian sperm is a
regulated secretion with unusual characteristics. One
of its most striking features is the lost of the outer acrosomal
membrane and the overlying plasma membrane as hybrid vesicles. We have
previously reported in human sperm that, by preventing the release of
calcium from the acrosome, the exocytic process can be arrested at a
stage where SNARE proteins are assembled in loose trans complexes. Transmission electron micrographs of sperm at this
stage showed that the acrosomes were profusely swollen, with deep
invaginations of the outer acrosomal membrane. The
protruding edges of these invaginations were tightly apposed (i.e.,
docked) to the plasma membrane. Docking was prevented when streptolysin
O-permeabilized sperm were stimulated in the presence of tetanus toxin
or botulinum neurotoxin C, two SNARE specific proteases.
We propose that SNAREs present in the plasma membrane interact
with SNAREs in the protruding edge of cup-shaped invaginations of the
outer acrosomal membrane to form trans complexes. Fusion pore opening
and expansion in this ring of apposed membranes would generate the
hybrid vesicles that are released during the acrosome reaction
