Lateral diffusion of a human sperm-head antigen during incubation in a capacitation medium and induction of the acrosome reaction in vitro

Abstract

An integral component of human spermatozoa, a glycoprotein of Mr 143,000 (two subunits of Mr 76,000 and 67,000) was recognized by the a-HS 1A.1 monoclonal antibody. The antigen was localized on the plasma membrane over the sperm head, as demonstrated by transmission electron microscopy. The antigen-antibody binding on gametes during changes in their functional state was followed by an indirect immunofluorescence assay of live human spermatozoa. In freshly ejaculated spermatozoa the antibody binding pattern revealed a patchwork quilt-like topography of the plasma membrane over the acrosome; the percentage of positive cells varied from 20 to 78% with a mean of 50% (n = 82). Incubation in a capacitation medium could increase this percentage up to 98%, revealing new epitopes in an energy-dependent and temperature-independent manner; concomitantly, a part of the antigen migrated in energy-independent and temperature-dependent manner and accumulated in a ring over the postacrosome. When an acrosome reaction was induced in vitro in the presence of Ca2+ with either A23187, ionomycin or human follicular fluid, the HS 1A.1 antigen migrated until immobilization in a well defined pattern around the equatorial segment (single band) or around the equatorial and postacrosomal segments (2 or, seldom, 3 bands). The new antigen localization resulted from a lateral diffusion of pre-existing molecules, occurred in only a few minutes, did not require energy and was temperature-dependent. At the same time, the well outlined large patch burst into a multitude of small spots before vanishing. this veil-like labelling was often observed in spermatozoa kept in the seminal plasma or treated with a metabolic poison. The HS 1A.1 antigen localization reflects surface changes induced by the incubation in a capacitation medium and the acrosome reaction. Apart from the regional heterogeneity of the plasma membrane of a single cell, as noted above, there were differences in the plasma membrane changes in individual spermatozoa from the same ejaculate as well as in semen samples from different donors. The new antibody binding pattern was often alike in successive ejaculates of the same donor. In patients consulting for infertility the percentage of positive cells was often low and migration of the antigen was slight or absent.

A rat sperm flagellar surface antigen that originates in the testis and is expressed on the flagellar surface during epididymal transit

“…The proteins previously reported to show possible mobility in the plasma membrane include galactosyltransferase on the mouse sperm head (Scully et al, 1987), PT-1 and PH-20 polypeptides on the guinea pig sperm head and flagellum (Primakoff and Myles, 1983;Myles and Primakoff, 1984;Cowan et al, 1986Cowan et al, , 1991, the 80K (No. 5.0 antigen) (Saxena et al, 1986a,b) and 78K proteins (P86/5 antigen) (Topfer-Petersen et al, 1990) on the boar sperm head, the 30K protein (Wolf et al, 1986) or 18K sialoglycoprotein (McKinnon et al, 1991) as ESA 152 antigen on the ram sperm surface, the 32K and 40K proteins (2B1 antigen) (Gaunt et al, 1983) and 23-33K multiplet proteins as CE9 (Petruszak et al, 1991) on the rat sperm flagellum, the 70K protein (DAG protein) on the rat sperm head and flagellum (Sylvester et al, 1984), and the 143K protein on the human sperm head (Villarroya and Scholler, 1987). Among these, the MC31 antigen is quite similar to CE9 (Petruszak et al, 1991) in terms of its molecular size, spatial localization, and possible redistribution.…”

Neoglycoproteins as carbohydrate antigens: Synthesis, analysis, and polyclonal antibody response

“…Based on our current, and previous results, we suggest that it may be possible to obtain strictly maltose-specific mAbs by generating sufficiently large monoclonal antibody libraries via mAb proteomics [35]. However, as only few strictly sugar-specific mAbs have been reported in the literature [36,37], we feel that the likelihood of obtaining such reagents is relatively low. We have to add that through extensive search in the literature, we were not able to find polyclonal antibody response to neoglycans with detectable specificity directed strictly to the sugar moiety.…”

Monoclonal antibody labelling of human spermatozoa: an electron microscope study

“…Such a misleading situation has been reported by Jones et al (1983). It is noteworthy that the distribution of this membrane-bound antigen undergoes important modifications with respect to its location on the sperm head and to the percentage of labelled cells during in-vitro capacitation and after induction of the acrosome reaction by a calcium ionophore, as assessed by immunofluorescence (Villarroya & Scholler, 1987).…”

“…This is to be compared with fluorescent patches scattered over the anterior head. With both techniques the distribution of the antigen over the apical region, the anterior and equatorial segments of the acrosome, showed individual variability (Villarroya & Scholler, 1987). Incubating sperm with diluted a-HS lA.l overnight at 4°C resulted in a similar labelling pattern.…”