Vesicles in the Subacrosomal Space and Partial Diaphragms in the Subacrosomal Nuclear Envelope of Round Spermatids of a Rat Injected Intravenously with Gold Labeled-Testosterone-Bovine Serum Albumin Conjugate: Vesicular Trafficking from Acrosome to Nucleus.

Abstract

Colloidal gold labeled-testosterone-bovine serum albumin conjugate (testosterone-BSA-gold) injected into the vascular system of rats is taken up by endocytosis into round spermatids. Based on observation of silver deposits indicating testosterone-BSA-gold with silver enhancement, we have suggested that testosterone-BSA-gold enters the nuclei through not only the postacrosomal nuclear envelope but also the subacrosomal nuclear envelope (SNE) via the acrosome (Nishimura and Nakano, 1997). However, it was unclear how testosterone-BSA-gold in the acrosome entered the nucleoplasm. Spermatids showing silver deposits on the subacrosomal space were observed under electron microscope without silver enhancement, to clarify the courses of translocation. In the spermatids, vesicles with the gold particles were seen in the subacrosomal space. Some of the vesicles were in contact with the SNE. A part of the outer nuclear membrane projected into the space. Furthermore, local single-bilayer nuclear membranes, which seemed to partially lack nuclear lamina, were present in the SNE. These results indicate the possibility that the vesicles mediate the transport of testosterone-BSA-gold from acrosome to nucleus, and that the vesicle membrane fuses with not only the outer nuclear membrane but also a shared bilayer in the SNE.

Steroid Hormones as Transporters to Carry Exogenous Macromolecules into the Target Cell Nuclei in Vivo

“…3). These results indicate the possibility that the membranes of vesicles fuse with shared bilayers in the SNE [30].…”

Transportation Course of Macromolecules to the Nucleus from the Extracellular Environment: Steroid Hormones’ Cellular Entry Mode Revisited

“…Two membranes of SNE are in close apposition. The continuity between the outer and inner nuclear membranes of SNE was observed successfully [13], indicating the possibility that there is hemifusion membrane in the SNE. Earlier, we found pores that are different from NPCs in nuclear export of baculovirus nucleocapsids.…”

“…In the spermatogenic cells of rat injected with testosterone-BSA-gold, the silver deposits were present on the cell membrane, vesicles, Golgi region, acrosome, subacrosomal space, both the post-acrosomal and the subacrosomal nuclear envelope, and the nucleoplasm [10,21]. In observations without silver enhancement, a single-bilayer nuclear membrane or a diaphragm was visible in the SNE [10,13]. In post-acrosomal nuclear envelope, the outer nuclear membrane was invaginated toward the inner nuclear membrane, and was likely to interact with the latter (Figure 1e) [10,21].…”