Localization of boar sperm proacrosin during spermatogenesis and during sperm maturation in the epididymis

Abstract

The localization of proacrosin was determined by using colloidal gold labeling and electron microscopy of boar germ cells during spermiogenesis to post-ejaculation. Proacrosin was first localized in round spermatids during the Golgi phase of spermiogenesis; it was associated with the electron-dense granule, or acrosomal granule that was conspicuous within the acrosome. It remained within the acrosomal granule during the cap and acrosome phases of spermiogenesis. At these stages, there was no apparent association of the proacrosin molecule with the acrosomal membranes. During the maturation phase of spermiogenesis, proacrosin was seen to become dispersed into all regions of the acrosome except the equatorial segment. When sperm from different segments of the epididymis and ejaculated sperm were examined, localization was observed throughout the acrosome except for the equatorial segment. Here proacrosin appeared to be localized on both the inner and outer acrosomal membranes as well as with the acrosomal matrix, although further studies are required to verify the membrane localization. No labeling was seen on the plasma membrane. These data suggest that the synthesis and movement of proacrosin to sites in the acrosome are controlled by an as yet unknown process. The absence of proacrosin on the plasma membrane of mature ejaculated sperm makes it unlikely that this enzyme plays a role in sperm-zona adhesion prior to capacitation.

Transport and rearrangement of the intra-acrosomal protein acrin1 (MN7) during spermiogenesis in the guinea pig testis

“…At this stage, acrin1 further drastically changed its location from the peripheral to the dorsal matrix region in the apical segment. Other acrosomal proteins such as human SP-10 (Kurth et al, 1991) and boar proacrosin (Bozzola et al, 1991), and the structural protein AM50 (Westbrook-Case et al, 1995) have also been shown to be redistributed at this stage, suggesting that the remodeling of acrosome shape may be involved in the final sorting and assembly of domain-specific proteins of the acrosomal matrix. Overall, the rearrangement of acrin1 during the acrosome and maturation phases seem to be closely related to the modifications in the acrosomal structural proteins.…”

Two Eye Guanylyl Cyclases Are Expressed in the Same Photoreceptor Cells and Form Homomers in Preference to Heteromers

“…The next day the samples were transferred into the same rinse buffer containing 0.1 M glycine. The ultrathin sections were prepared from LR White-embedded tissue and used to perform colloidal gold labeling as described (20).…”

Organization and modifications of sperm acrosomal molecules during spermatogenesis and epididymal maturation

“…Several intra-acrosomal proteins exhibit modifications of the molecular weights during epididymal maturation. For example, proacrosin of boar spermatozoa appears to be localized on the IAM and OAM as well as in the acrosomal matrix (Bozzola et al, 1991). Molecular size reduction is reported in the spermatozoa of rabbit (Mukerji and Meizel, 1979), boar (Baba et al, 1989), guinea pig (Anakwe et al, 1991), rat (NagDas et al, 1992), and human (Baba et al, 1994).…”

“…In these stages, acrosomal proteins are generally transported from the endoplasmic reticulum into the developing acrosomal system through the Golgi apparatus until the end of the cap phase (Clermont and Tang, 1985). For example, boar proacrosin (Bozzola et al, 1991), guinea pig AM 50 (Westbrook-Case et al, 1995), rat and guinea pig acrin1 (Tanii et al, 1994;Yoshinaga et al, 2000), and mouse sp56 (Kim et al, 2001a) first appear in association with Golgi-derived granules and the developing acrosomal vesicle of early spermatids (Fig. 2a).…”

“…2a-c; Yoshinaga et al, 2000). Other acrosomal proteins such as boar proacrosin (Bozzola et al, 1991) and AM50 (Westbrook-Case et al, 1995) are also relocated. Acrogranin (granulin/epithelin precursor) ) is reduced in its synthesis during late spermiogenesis (Anakwe and Gerton, 1990).…”