Loss of Sperm Surface Sialic Acid Induces Phagocytosis: An Assay with a Monoclonal Antibody T21, Which Recognizes a 54K Sialoglycoprotein

Abstract

Using a monoclonal antibody T21, we reported that a mouse sperm maturation-associated antigen sialoglycoprotein of 54000 daltons (54K sialoglycoprotein) was secreted at the distal caput to proximal corpus epididymidis and that the 54K sialoglycoprotein had a hidden determinant (cryptodeterminant), which could be eliminated by sialidase treatment (Toshimori et al. (1988): Histochemistry 90: 195-200; (1990a): Biol Reprod 42:151-160; (1990b): Arch Histol Cytol 53:339-349). This study evaluated the mouse sperm susceptibility to phagocytosis by macrophage in vitro. Comparisons were made between sperm from the caput epididymidis (caput sperm) incubated in modified Krebs Ringer's solution (MKR) and caput sperm incubated in MKR containing cauda fluid, and between sialylated (sialidaseuntreated) sperm from the corpus and cauda epididymidis (corpuslcauda sperm) and desialylated (sialidase-treated) corpuslcauda sperm. The results showed that macrophages were least actively engaged in phagocytosis for caput sperm incubated in MKR containing cauda fluid, and most active for desialylated corpuslcauda sperm. Incubation of caput sperm in MKR containing cauda fluid revealed that the 54K sialoglycoprotein in cauda fluid could be bound to the flagellar surface of caput sperm. These results together with previous findings strongly suggest that the 54K sialoglycoprotein bound to immature sperm during maturation in the epididymis is implicated in the protection of sperm from phagocytosis with the aid of sialic acid residues.Key Words: Mouse; Sperm; Epididymal maturation; Sialic acid; Phagocytosis. INTRODUCTIONA major function of the mammalian epididymal epithelium is to synthesize and secrete glycoproteins, and therefore both the synthetic activity and the nature of the secretory products vary along the excurrent duct, resulting in changes in composition of the duct fluid [26]. These secretory products of the epididymis are believed to be involved in the changes that spermatozoa undergo during maturation which causes them to gain functions essential for fertilizing ability such as zona pellucida binding and forward motility [3,4, 401. In general, cell surface negative charge is chiefly due to sialic acid residues [7,17, 281, and the bound sialic acid residues have significant biological functions, such as masking of antigens (anti-recognition) and cell-cell recognition in some cells [24,27, 281. In the epididymis, sialic acid residues are reported to be secreted by the epithelium as a terminal sugar of sialoglycoproteins and bound to sperm surface [ l , 6, 12-14, 18, 23, 25, 35, 36, 381. In previous studies using a monoclonal antibody T21, we reported evidences that a sperm maturation-associated antigen sialoglycoprotein of 54000 daltons (54K sialoglycoprotein) has a hidden determinant (cryptodeterminant) [3 1, 32, 331. From these evidences, we reported a hypothetical interaction of the 54K sialoglycoprotein with sperm flagellar plasma membrane, especially in consideration of the location of sialic acid residues on the molecule [3...

Histochemical Analysis of Glycoconjugates in the Disseminate Prostate Gland of the Wild Boar (Sus scrofa riukiuanus)

“…In addition, it has been established that O-acetylated sialic acids prevent the invasion of pathogens and influence the metabolic process of sialic acids [10,26]. On the other hand, the removal or loss of sialic acids from sperm surface is known to be necessary events for capacitation and zona pellucida recognition [15] and to induce phagocytosis of spermatozoa by macrophage [32]. In the wild boar, the existence of non-or O-acetylated sialic acids in the secretions of the disseminate prostate gland appears to play an important role for the stabilization of spermatozoa in terms of their metabolism, motility, and protection during ejaculation and ensuing transition to the female genital tract.…”

Desialylation of Spermatozoa and Epithelial Cell Glycocalyx Is a Consequence of Bacterial Infection of the Epididymis

“…Moreover, many sialylated and polysialylated glycoproteins are integrated into the plasma membrane of spermatozoa during epididymal transit (34,35). These glycoproteins inhibit, inter alia, in a sialic acid-dependent way the phagocytosis by leukocytes as seen in murine spermatozoa (30,36). In this regard, the substantial loss of sialic acid residues during epididymitis could prompt phagocytosis of spermatozoa during transit through the epididymis and/or the female reproductive tract, as already indicated (30,37).…”

“…Under normal conditions, neuraminidases are only activated in the female reproductive tract as a consequence of capacitation and/or acrosome reaction (8,10,12,29). Premature release of neuraminidases prior ejaculation is usually avoided, as untimely desialylation could result in elimination of spermatozoa by phagocytic cells (30). Under pathophysiological conditions such as bacterial epididymitis, considerable premature exocytosis of the acrosome has been observed in vivo and in vitro, which contributes substantially to the loss of fertilizing capacity, as shown by subsequent in vitro fertilization experiments in mice (5).…”

The origin of a sperm maturation-associated antigen, 54K sialoglycoprotein; an immunohistochemical study with monoclonal antibody MC81 in the mouse.

“…This will be true especially when antibodies are used for analyses of a membrane-bound sialoglycoprotein which is presumed to have a cryptodeterminant. The major antigen of MC81 is though to be identical to the 54K sialoglycoprotein which is specifically recognized by T21 (35,36,40) in terms of its cellular localization on mouse mature sperm flagellar surfaces from the corpus and cauda epididymidis, its proximal shift, its sialic acid-related masking and its molecular size and acidic nature. In addition, the epitope for the MC81 antibody is supposed to be present on sugar chains based on the observation that the epitope was sensitive to periodate treatment in a dose-dependent manner, as well as in the case of T21 (36).…”

“…Recently, we reported that monoclonal antibody T21 specifically recognizes a mouse sperm maturationassociated antigen of 54,000 dalton (54K) sialoglycoprotein; The 54K protein is considered to be secreted in the distal caput epididymidis, bound to the flagellar surface of sperm during transit in the epididymis, and involved in the protection of sperm from phagocytic cells (35)(36)(37)(38)40).…”