Sperm-Activating Proteins Obtained from the Herring Eggs Are Homologous to Trypsin Inhibitors and Synthesized in Follicle Cells

Abstract

The activation of sperm motility by the egg is an ubiquitous phenomenon in the animal kingdom, but the molecules by which the egg activates sperm motility have been clarified in only a few invertebrate species. In the Pacific herring, Clupea pallasii, mature unfertilized eggs release the sperm-activating proteins which are prerequisite to successful fertilization. Complementary DNA clones encoding herring sperm-activating proteins were isolated from a herring ovarian complementary DNA library and amino acid sequences were deduced. The herring sperm-activating protein(s) is a secretory product(s) with a strong homology to Kazal-type trypsin inhibitors, such as mammalian acrosin inhibitors. The sperm-activating proteins were globally distributed in the outermost layer of the egg chorion and its gene was found to be expressed in the follicle cells which surround developing oocytes. These results suggest that in the Pacific herring, trypsin inhibitor-like proteins are synthesized in the follicle cells, secreted, accumulated in the egg chorion during oocyte development, and released into the milieu at spawning to activate the motility of spermatozoa at the time of gamete interaction.

Marine fish spermatozoa: racing ephemeral swimmers

“…The motility initiation is regulated by a reverse Na C /Ca 2C exchanger (Vines et al 2002) but some components of the chorion are needed (Oda et al 1995): the herring sperm activating peptide (HSAP) and the sperm motility initiation factor (SMIF). The HSAP has protease inhibitor motifs (Oda et al 1998) which binds to an endopeptidase of the flagellar membrane (Yoshida et al 1999). The SMIF is a 105 kDa glycoprotein localized in the chorion part surrounding the micropyle that induces a trajectory switch from linear in 'free' SW to helicoidal in the micropylar funnel.…”

Motility initiation in herring sperm is regulated by reverse sodium-calcium exchange

“…13); both SMIF-induced and NaF-induced motility initiation require the presence of [Ca 2ϩ ] o (minimum of 1 mM). Herring sperm motility also can be initiated by herring sperm activating peptides (HSAPs) that rapidly diffuse away from the eggs at spawning (19)(20)(21).The requirement for decreased [Na ϩ ] o and the presence of [Ca 2ϩ ] o suggest that a sodium-calcium (Na ϩ ͞Ca 2ϩ ) exchange could occur during ligand-induced herring sperm motility initiation. In this study, we make the finding that there is an efflux of Na ϩ and an influx of Ca 2ϩ during ligand-induced motility initiation in herring sperm and this movement of ions is caused by reverse-Na ϩ ͞Ca 2ϩ exchange.…”

“…13); both SMIF-induced and NaF-induced motility initiation require the presence of [Ca 2ϩ ] o (minimum of 1 mM). Herring sperm motility also can be initiated by herring sperm activating peptides (HSAPs) that rapidly diffuse away from the eggs at spawning (19)(20)(21).…”

Purification and characterization of prolyl endopeptidase from the Pacific herring, Clupea pallasi, and its role in the activation of sperm motility

“…6). Recently, the cDNA sequence of the HSAP showed that the amino acid sequence is homologous to Kazal-type trypsin inhibitor (Oda et al 1998), such as the acrosin inhibitor (Zaneveld et al 1972;1973), or pancreatic secretory trypsin inhibitor (Kikuchi et al 1985), etc., …”

“…pI ϭ 4.8,4.9,5.0,5.1,5.4), with average molecular masses of 8 kDa, have been purified from egg conditioning medium (Oda et al 1995). The cDNA sequence analysis showed that the amino acid sequence of the HSAP is homologous to Kazal-type trypsin inhibitors (Oda et al 1998), such as an acrosin inhibitor (Zaneveld et al 1972;Zaneveld et al 1973), or a pancreatic secretory trypsin inhibitor (Kikuchi et al 1985). These inhibitor, benzyloxycarbonyl-L-thioprolinethioprolinal (Z-Thiopro-thioprolinal;Tsuru et al 1988) or substrates suggest that the PEP concerns the activation of flagellar motility of herring spermatozoa.…”