β-Microseminoprotein in human spermatozoa and its potential role in male fertility

Abstract

Abstractb-Microseminoprotein (MSMB) is one of the most abundant proteins in human seminal plasma. The objectives of this study were: (1) to purify MSMB from seminal plasma (SP) and generate antibodies against the pure protein; (2) to investigate the interaction of MSMB with ejaculated spermatozoa and its possible effect on the spontaneous acrosome reaction (AR); and (3) to quantify MSMB content in SP and examine its relationship with the clinical sperm parameters. MSMB was purified from SP and its presence on the sperm surface was examined by indirect immunofluorescence using a specific polyclonal antibody. The effect of MSMB on the AR was evaluated using guinea pig epididymal spermatozoa as a model. MSMB quantification assay was performed with a two-site binding ELISA using two polyclonal antibodies against MSMB. MSMB was assessed in semen samples from fertile donors (controls) and subfertile patients according to World Health Organization criteria. MSMB was detected on the sperm surface and mainly localized to the acrosomal region of the head and neck. A significant spontaneous AR inhibition was observed when guinea pig epididymal spermatozoa were preincubated with MSMB. Finally, MSMB was significantly increased in subfertile patients when compared with fertile controls (P!0.02). The association of MSMB to the sperm surface, the inhibitor effect on the spontaneous AR and the increased MSMB levels found in SP in subfertile men suggests a relationship between this protein and semen quality and a possible role in the process of fertilization. Reproduction (2008) 136 157-166

Reproductive tissue expression and sperm localization of porcine beta-microseminoprotein

“…Moreover, an increased MSP level has been found in subfertile men, suggesting a relationship between this protein and semen quality in males. Additionally, some authors have expressed a possible involvement of MSP in the sperm-zona pellucida interaction (Franchi et al 2008). Interestingly, our findings that MSP disappears from the sperm surface after capacitation but is still present in the sperm acidic extract containing intra-acrosomal proteins suggest further possible roles of MSP in the reproductive process.…”

“…On the basis of the suggested structure and physical features, the interaction of porcine MSP with the plasma membrane is likely because of the electrostatic interactions between the MSP and the integral proteins (Wang et al 2005;Franchi et al 2008). During ejaculation, boar spermatozoa receive a protective protein layer formed by seminal plasma components Fig.…”

“…In human spermatozoa, MSP has been reported to be attached to the cell membrane of the head but not to the tail (Ito et al 1989). Immunofluorescence has revealed human MSP in the acrosomal region and in the equatorial segment of the head or on the neck of ejaculated spermatozoa (Franchi et al 2008). On the other hand, in the macaque, MSP has been detected only on the sperm flagellum (Tollner et al 2004).…”

Crystal Structure of Prostate Secretory Protein PSP94 Shows an Edge-to-Edge Association of two Monomers to Form a Homodimer

“…The final, refined atomic model contains 369 out of 376 amino acid residues in four polypeptide chains of PSP94. The missing region is a flexible loop (amino acids [10][11][12][13][14][15][16] in chain A. The atomic coordinates have been deposited in the Protein Data Bank (PDB) with the accession code 3IX0.…”

“…[7][8][9] PSP94 has also been shown to be a motility inhibitor of sperm 10 and an inhibitor of sperm acrosome reaction. 11 Apart from reproductive tissues, PSP94 has also been detected in several nonreproductive tissues, such as the respiratory and gastric tract tissues, and in both males and females. 12 PSP94 homologues have also been identified in several other mammals [13][14][15] and nonmammalian species.…”