Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.25.1 (proteasome)
 28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sperm proteasomes are thought to be involved in sperm binding to and in sperm penetration through the vitelline coat of the eggs of the stolidobranch ascidian Halocynthia roretzi. However, it is not known whether they are involved in the fertilization of eggs of other ascidians. Therefore, we investigated whether sperm proteasomes are also involved in the fertilization of the eggs of the primitive phlebobranch ascidian Ciona intestinalis. Fertilization of the eggs of C. intestinalis was potently inhibited by the proteasome inhibitors MG115 and MG132 but not by the cysteine protease inhibitor E-64-d. On the other hand, neither fertilization of the vitelline coat-free eggs nor sperm binding to the vitelline coat was inhibited by the two proteasome inhibitors at a concentration sufficient to inhibit fertilization of intact eggs. These results indicate that the proteasome plays an essential role in sperm penetration through the vitelline coat rather than in sperm binding to the coat or in sperm-egg membrane fusion. The proteasome activity, which was detected in the sperm extract using Suc-Leu-Leu-Val-Tyr-MCA as a substrate, was strongly inhibited by both MG115 and MG132, and was weakly inhibited by chymostatin, whereas neither leupeptin nor E-64-d inhibited the activity. The molecular mass of the enzyme was estimated to be 600-kDa by Superose 12 gel filtration, and the activity in sperm extract was immunoprecipitated with an anti-proteasome antibody. These results indicate that the proteasome present in sperm of C. intestinalis is involved in fertilization, especially in the process of sperm penetration through the vitelline coat, probably functioning as a lysin.
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PMID:Participation of sperm proteasome in fertilization of the phlebobranch ascidian Ciona intestinalis. 966 33

Fertilization is a precisely controlled process involving many gamete molecules in sperm binding to and penetration through the extracellular matrix of the egg. After sperm bind to the extracellular matrix (vitelline coat), they undergo the acrosome reaction which exposes and partially releases a lytic agent called "lysin" to digest the vitelline coat for the sperm penetration. The vitelline coat sperm lysin is generally a protease in deuterostomes. The molecular mechanism of the actual degradation of the vitelline coat, however, remains poorly understood. In order to understand the lysin system, we have been studying the fertilization mechanism in ascidians (Urochordata) because we can obtain large quantities of gametes which are readily fertilized in the laboratory. Whereas ascidians are hermaphrodites, which release sperm and eggs simultaneously, many ascidians, including Halocynthia roretzi, are strictly self-sterile. Therefore, after sperm recognize the vitelline coat as nonself, the sperm lysin system is thought to be activated. We revealed that two sperm trypsin-like proteases, acrosin and spermosin, the latter of which is a novel sperm protease with thrombin-like substrate specificity, are essential for fertilization in H. roretzi. These molecules contain motifs involved in binding to the vitelline coat. We found that the proteasome rather than trypsin-like proteases has a direct lytic activity toward the vitelline coat. The target for the ascidian lysin was found to be a 70-kDa vitelline coat component called HrVC70, which is made up of 12 EGF-like repeats. In addition to the proteasome system, the ubiquitination system toward the HrVC70 was found to be necessary for ascidian fertilization. In this review, I describe recent progress on the structures and roles in fertilization of the two trypsin-like proteases, acrosin and spermosin, and also on the novel extracellular ubiquitin-proteasome system, which plays an essential role in the degradation of the ascidian vitelline coat.
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PMID:Ascidian sperm lysin system. 1201 76

The roles of sperm proteasomes in fertilization were investigated in the sea urchin Pseudocentrotus depressus. Two proteasome inhibitors, MG-132 and MG-115, inhibited fertilization at 100 microM, whereas chymostatin and leupeptin showed no inhibition. Among three proteasome substrates, Z-Leu-Leu-Glu-MCA showed the strongest inhibition toward fertilization. MG-132 inhibited the egg-jelly-induced, but not ionomycin-induced, acrosome reaction. In addition, MG-132, but not E-64-d, inhibited fertilization of dejellied eggs by acrosome-reacted sperm. MG-132 showed no significant inhibition toward the binding of reacted sperm to the vitelline layer. Proteasomes were detected by Western blotting in the acrosomal contents, which are partially released upon exocytosis. We also found that the inhibition pattern of the caspase-like activity of the proteasome in the acrosomal contents by chymostatin and proteasome inhibitors coincided well with their inhibitory abilities toward fertilization. Furthermore, the vitelline layer of unfertilized eggs appears to be ubiquitinated as revealed by immunocytochemistry and Western blotting. Extracellular ATP, required for the degradation of ubiquitinated proteins by the proteasome, was also necessary for fertilization. These results indicate that the sperm proteasome plays a key role not only in the acrosome reaction but also in sperm penetration through the vitelline envelope, most probably as a lysin, during sea urchin fertilization.
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PMID:Sperm proteasomes are responsible for the acrosome reaction and sperm penetration of the vitelline envelope during fertilization of the sea urchin Pseudocentrotus depressus. 1758 94

The sperm proteasome has been reported to be involved in sperm penetration through the proteinaceous egg-coat during fertilization in ascidians and mammals. However, such an extracellular role for the sperm proteasome in fertilization is not known in other deuterostomes. Here, we investigated the effects of two proteasome inhibitors on fertilization of the sea urchin Anthocidaris crassispina. Two proteasome inhibitors, MG-132 and MG-115, inhibited fertilization, whereas E-64-d, chymostatin or leupeptin showed no inhibition at 100 microM. MG-132 inhibited the egg-jelly-induced acrosome reaction, but not the reaction induced by the Ca(2+) ionophore ionomycin. MG-132 and MG-115, but not E-64-d, inhibited the fertilization of dejellied eggs by acrosome-reacted sperm. Furthermore, MG-132-susceptible proteasome activity was detected in the acrosomal contents. These results suggest that the sperm proteasome plays a key role not only in the acrosome reaction, in particular, in a process before the increase in intracellular Ca(2+) concentration but also in the sperm penetration through the vitelline coat, most probably as a lysin.
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PMID:Effects of proteasome inhibitors on fertilization of the sea urchin Anthocidaris crassispina. 1760 76

Despite decades of research, the mechanism by which the fertilizing spermatozoon penetrates the mammalian vitelline membrane, the zona pellucida (ZP) remains one of the unexplained fundamental events of human/mammalian development. Evidence has been accumulating in support of the 26S proteasome as a candidate for echinoderm, ascidian and mammalian egg coat lysin. Monitoring ZP protein degradation by sperm during fertilization is nearly impossible because those few spermatozoa that penetrate the ZP leave behind a virtually untraceable residue of degraded proteins. We have overcome this hurdle by designing an experimentally consistent in vitro system in which live boar spermatozoa are co-incubated with ZP-proteins (ZPP) solubilized from porcine oocytes. Using this assay, mimicking sperm-egg interactions, we demonstrate that the sperm-borne proteasomes can degrade the sperm receptor protein ZPC. Upon coincubation with motile spermatozoa, the solubilized ZPP, which appear to be ubiquitinated, adhered to sperm acrosomal caps and induced acrosomal exocytosis/formation of the acrosomal shroud. The degradation of the sperm receptor protein ZPC was assessed by Western blotting band-densitometry and proteomics. A nearly identical pattern of sperm receptor degradation, evident already within the first 5 min of coincubation, was observed when the spermatozoa were replaced with the isolated, enzymatically active, sperm-derived proteasomes. ZPC degradation was blocked by proteasomal inhibitors and accelerated by ubiquitin-aldehyde(UBAL), a modified ubiquitin protein that stimulates proteasomal proteolysis. Such a degradation pattern of ZPC is consistent with in vitro fertilization studies, in which proteasomal inhibitors completely blocked fertilization, and UBAL increased fertilization and polyspermy rates. Preincubation of intact zona-enclosed ova with isolated active sperm proteasomes caused digestion, abrasions and loosening of the exposed zonae, and significantly reduced the fertilization/polyspermy rates after IVF, accompanied by en-mass detachment of zona bound sperm. Thus, the sperm borne 26S proteasome is a candidate zona lysin in mammals. This new paradigm has implications for contraception and assisted reproductive technologies in humans, as well as animals.
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PMID:Sperm proteasomes degrade sperm receptor on the egg zona pellucida during mammalian fertilization. 2138 44