SLLP1, A Unique, Intra-acrosomal, Non-bacteriolytic, c Lysozyme-Like Protein of Human Spermatozoa1

Abstract

We report the presence of a unique, non-bacteriolytic, c (chicken or conventional type) lysozyme-like protein, SLLP1, in the acrosome of human sperm. C lysozymes are bacteriolytic and can also bind to N-acetylglucosamines linked by beta-1,4 glycosidic bonds. Most of the invariant residues (17 out of 20), including all the cysteines, were conserved in SLLP1, but the two catalytic residues E35 and D52 of c lysozymes were replaced with T and N, respectively. The full-length cDNA encodes a protein of 215 aa with a predicted protease cleavage site between A87 and K88. The processed form of SLLP1, which showed an exon-intron organization similar to human c lysozyme, was the major isoform in the acrosome of ejaculated sperm. As expected, based on its sequence, the mature protein secreted from yeast showed no bacteriolytic activity. A significant decrease (54%, P < or = 0.001) in the number of sperm bound to zona-free hamster eggs was observed in the presence of antisera to recombinant SLLP1. SLLP1 mRNA (size, approximately 1 kb) appeared to be expressed only in the testis and in the Burkitt lymphoma Raji cell line. The gene SPACA3 encodes SLLP1 and contains five exons at locus 17q11.2. Because of its typical c lysozyme-like sequence, genomic organization, conservation of putative substrate-binding sites even in the absence of catalytic residues, and localization in the acrosomal matrix, we hypothesize that, after acrosome reaction, SLLP1 could be a potential receptor for the egg oligosaccharide residue N-acetylglucosamine, which is present in the extracellular matrix over the egg plasma membrane, within the perivitelline space, pores of zona pellucida, and cumulus layers.

SPACA3gene variants in a New Zealand cohort of infertile and fertile couples

“…Wagner, unpublished). This pattern of gonad/gamete-specifi c expression also supports the concept that SPRASA has an important role in fertility (Herrero et al, 2005; 2 D. Prendergast et al Human Fertility Mandal et al, 2003;Wagner, 2009). While we discovered SPRASA as the antigen for antisperm antibodies in some infertile men, the association of SPRASA with human infertility has not been investigated further.…”

“…SPRASA is a member of the c-type lysozyme/ alpha-lactalbumin family (Chiu et al, 2004;Mandal et al, 2003), and human SPRASA is encoded by a gene ( SPACA3 ) at chromosomal locus 17q11.2 (Mandal et al, 2003). SPRASA is known to be the target for antisperm antibodies in some infertile men, and this protein has been shown to have roles in sperm -oocyte binding and early embryo development in murine, hamster, or bovine models (Chiu et al, 2004;Mandal et al, 2003;Zhang et al, 2005;A. Wagner, unpublished).…”

Elevation of transcription factor Islet-1 levels in vivo increases β-cell function but not β-cell mass

“…3D), although neither of these genes was detected in the microarray study, likely due to sensitivity issues with gene expression arrays. 32 We also attempted to confirm an increase in the expression of several other genes that may be involved in secretion, including glutamate receptor (Grin2c), 33 non voltage-gated sodium channel (Scnn1a), 34,35 and sperm acrosome associated 1 (Spaca1), 36,37 but were unable to validate upregulation of these genes. Taken together, our results suggest that Isl-1 may mediate increased β-cell functionality through a subset of genes involved in protein trafficking, metabolism, development, signal transduction and transcriptional regulation.…”

Characterisation of Lyzls in mice and antibacterial properties of human LYZL6

“…In the human male reproductive system, four c-type lysozyme genes (LYZL2, SPACA3, LYZL4 and LYZL6) have been identified 4,6 and are all highly expressed in the testis or epididymis. Mandal et al 6 showed that antisera to a sperm lysozyme-like protein (SLLP1), encoded by the SPACA3 gene, block sperm-egg binding in the hamster-oocyte penetration assay, indicating a possible role of SLLP1 in sperm-oocyte binding or penetration.…”

“…Mandal et al 6 showed that antisera to a sperm lysozyme-like protein (SLLP1), encoded by the SPACA3 gene, block sperm-egg binding in the hamster-oocyte penetration assay, indicating a possible role of SLLP1 in sperm-oocyte binding or penetration. There are four c-type lysozymes (Lyzl1, Lyzl3/ Spaca3, Lyzl4 and Lyzl6) in mice; a fertilisation role has been shown for Lyzl4 and Spaca3 in mice, 7,8 but the function of the remaining two mouse c-type lysozyme genes is not clear.…”