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Chymotrypsin and Peptidylglutamyl peptidase indicating that proteasomes of
spermatozoa with neck abnormalities were endowed with deficient proteolytic
machineries (Morales et al.
2004
;Raweetal.
2008
). The important role of these
organelles is also supported by Platts et al. (
2007
) who reported that the major cellular
system negatively disrupted in teratozoospermia was the ubiquitin-proteasome
pathway. We hypothesized that the failure of centriolar release after sperm penetration
was due to insufficiency of proteasome-dependent proteolytic disassembly of the
sperm connecting piece. In bovine IVF experiments with pharmacologic and immu-
nologic neutralization of proteasomes, aster development and pronuclear apposition
were markedly inhibited (Fig.
2.6
), (Rawe et al.
2008
). Proteasomes and polyubiq-
uitinated proteins were recruited around the sperm connecting piece. These
conglomerates (''aggresomes'', Johnston et al.
1998
,seeFig
2.6b, b'
) may represent
failed attempts to overcome proteasome insufficiency when their capacity to degrade
ubiquitinated proteins is exceeded. These findings point to the male complement
of proteasomes as probably involved in the release of a functional centriole after
proteolytic degradation of the sperm connecting piece. Similar features have been
reported by Rawe et al. (
2008
) in zygotes from couples with spontaneous post-ICSI
fertilization failure.
The assembly of such a complex structure as the sperm neck, with centrioles
encased by a shield of dense proteins organized in the connecting piece and its
sequential disassembly into the zygote are processes for which pathways still have
to be successfully worked out. The studies summarized in this chapter highlight
the central role played by the sperm neck ubiquitin-proteasome system in early
zygote development and encourage further investigation on the physiopathology of
sperm-related fertility failures to fully expose the basic mechanisms involved.
Acknowledgments This chapter was the result of extensive review of the literature on sperm
centrosomes and centrosome-related sperm pathologies, including previous publications of our
group, in particular Chemes et al.
1978
,
1987b
,
1999
; Rawe et al.
2002
,
2008
.
References
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