Showing papers on "Acrosome reaction published in 2005"
TL;DR: It is concluded that male fertility varies substantially in natural populations of Iberian red deer and that, when sperm numbers are equal, it is determined mainly by sperm swimming velocity and sperm morphology.
Abstract: Male reproductive success is determined by the ability of males to gain sexual access to females and by their ability to fertilize ova. Among polygynous mammals, males differ markedly in their reproductive success, and a great deal of effort has been made to understand how selective forces have shaped traits that enhance male competitiveness both before and after copulation (i.e., sperm competition). However, the possibility that males also may differ in their fertility has been ignored under the assumption that male infertility is rare in natural populations because selection against it is likely to be strong. In the present study, we examined which semen traits correlate with male fertility in natural populations of Iberian red deer (Cervus elaphus hispanicus). We found no trade-offs between semen traits. Our analyses revealed strong associations between sperm production and sperm swimming velocity, sperm motility and proportion of morphologically normal spermatozoa, and sperm viability and acrosome integrity. These last two variables had the lowest coefficients of variation, suggesting that these traits have stabilized at high values and are unlikely to be related to fitness. In a fertility trial, our results show a large degree of variation in male fertility, and differences in fertility were determined mainly by sperm swimming velocity and by the proportion of morphologically normal sperm. We conclude that male fertility varies substantially in natural populations of Iberian red deer and that, when sperm numbers are equal, it is determined mainly by sperm swimming velocity and sperm morphology. acrosome reaction, gamete biology, male reproductive tract, sperm, sperm motility and transport
248 citations
TL;DR: It is demonstrated that human sperm express the CB(1), but not CB(2), cannabinoid receptor (CB-R) subtype located in the head and middle piece of the sperm, which negatively influences important sperm functions and suggests a possible role for the cannabinoid system in the pathogenesis of some forms of male infertility.
Abstract: Cannabinoids and endocannabinoids negatively influence sperm functions. These substances have been demonstrated in many mammalian tissues, including male and female reproductive tracts, and previous studies have shown the presence of functional receptors for cannabinoids in human sperm. The present study, by means of RT-PCR and Western blot techniques, demonstrates that human sperm express the CB(1), but not CB(2), cannabinoid receptor (CB-R) subtype located in the head and middle piece of the sperm. The activation of this receptor by anandamide reduces sperm motility and inhibits capacitation-induced acrosome reaction. Activation of the CB(1)-R did not induce any variation in sperm intracellular calcium concentrations, but produced a rapid plasma membrane hyperpolarization that was reduced by the K(+) channel blocker tetraethylammonium. The effects of anandamide on human sperm motility were dependent on the reduction of sperm mitochondrial activity as determined by rhodamine 123 fluorescence. The specificity of anandamide effects in human sperm were confirmed by the effects of the CB(1)-R antagonist SR141716. These findings provide additional evidence that human sperm express functional CB(1)-R, the activation of which negatively influences important sperm functions, and suggest a possible role for the cannabinoid system in the pathogenesis of some forms of male infertility.
218 citations
TL;DR: It is shown that sperm cells have a complete and efficient endocannabinoid system, and that activation of cannabinoid or vanilloid receptors controls, at different time-points, sperm functions required for fertilization.
Abstract: Anandamide (AEA) is the endogenous ligand of cannabinoid (CB) receptors, and as such it plays several central and peripheral activities. Regulation of female fertility by AEA has attracted growing interest, yet a role for this endocannabinoid in controlling sperm function and male fertility in mammals has been scarcely investigated. In this study we report unprecedented evidence that boar sperm cells have the biochemical machinery to bind and degrade AEA, i.e. type-1 cannabinoid receptors (CB1R), vanilloid receptors (TRPV1), AEA-synthesizing phospholipase D (NAPE-PLD), AEA transporter (AMT) and AEA hydrolase (FAAH). We also show that the non-hydrolyzable AEA analogue methanandamide reduces sperm capacitation and, as a consequence, inhibits the process of acrosome reaction (AR) triggered by the zona pellucida, according to a cyclic AMP-dependent pathway triggered by CB1R activation. Furthermore, activation of TRPV1 receptors seems to play a role of stabilization of the plasma membranes in capacitated sperm, as demonstrated by the high incidence of spontaneous AR occurring during the cultural period when TRPV1 activity was antagonized by capsazepine. We show that sperm cells have a complete and efficient endocannabinoid system, and that activation of cannabinoid or vanilloid receptors controls, at different time-points, sperm functions required for fertilization. These observations open new perspectives on the understanding and treatment of male fertility problems.
203 citations
TL;DR: In order to fertilize, the mammalian spermatozoa should reside in the female reproductive tract for several hours, during which they undergo a series of biochemical modifications collectively called capacitation, a process which enables sperm to penetrate into the egg and fertilize it.
Abstract: In order to fertilize, the mammalian spermatozoa should reside in the female reproductive tract for several hours, during which they undergo a series of biochemical modifications collectively called capacitation. Only capacitated sperm can undergo the acrosome reaction after binding to the egg zona pellucida, a process which enables sperm to penetrate into the egg and fertilize it. Polymerization of globular (G)-actin to filamentous (F)-actin occurs during capacitation, depending on protein kinase A activation, protein tyrosine phosphorylation, and phospholipase D activation. F-actin formation is important for the translocation of phospholipase C from the cytosol to the sperm plasma membrane during capacitation. Prior to the occurrence of the acrosome reaction, the F-actin should undergo depolymerization, a necessary process which enables the outer acrosomal membrane and the overlying plasma membrane to come into close proximity and fuse. The binding of the capacitated sperm to the zona pellucida induces a fast increase in sperm intracellular calcium, activation of actin severing proteins which break down the actin fibers, and allows the acrosome reaction to take place.
193 citations
TL;DR: Certain sperm ion channels are turning out to be unique, making them attractive targets for contraception and for the discovery of novel signaling complexes.
Abstract: Generating new life in animals by sexual reproduction depends on adequate communication between mature and competent male and female gametes. Ion channels are instrumental in the dialogue between sperm, its environment, and the egg. The ability of sperm to swim to the egg and fertilize it is modulated by ion permeability changes induced by environmental cues and components of the egg outer layer. Ca(2+) is probably the key messenger in this information exchange. It is therefore not surprising that different Ca(2+)-permeable channels are distinctly localized in these tiny specialized cells. New approaches to measure sperm currents, intracellular Ca(2+), membrane potential, and intracellular pH with fluorescent probes, patch-clamp recordings, sequence information, and heterologous expression are revealing how sperm channels participate in fertilization. Certain sperm ion channels are turning out to be unique, making them attractive targets for contraception and for the discovery of novel signaling complexes.
159 citations
TL;DR: Results suggest that in the mouse, Hyal5 may function principally as a "cumulus matrix depolymerase" in the sperm penetration through the cumulus mass and in the local hyaluronan hydrolysis near or on the surface of the egg zona pellucida to enable the proximal region of sperm tail to move freely.
Abstract: A glycosylphosphatidylinositol (GPI)-anchored hyaluronidase, PH-20, on the sperm surface has long been believed to assist sperm penetration through the cumulus mass surrounding the eggs. However, mouse sperm lacking PH-20 were still capable of penetrating the cumulus mass despite a delayed dispersal of cumulus cells. Intriguingly, a 55-kDa hyaluronan-hydrolyzing protein was abundantly present in wild-type and PH-20-deficient mouse sperm. In this study, we purified the 55-kDa mouse protein from soluble protein extracts released from epididymal sperm by acrosome reaction and identified as a hyaluronidase, Hyal5. Hyal5 was exclusively expressed in the testis and formed a 160-kbp gene cluster together with Hyalp1, Hyal4, and Ph-20 on mouse chromosome 6. Hyal5 was a single-chain hyaluronidase present on the plasma and acrosomal membranes of sperm presumably as a GPI-anchored protein. Moreover, hyaluronan zymography revealed that Hyal5 is enzymatically active in the pH range 5–7 and inactive at pH 3 and 4. Both Hyal5-enriched PH-20-free soluble protein extracts and PH-20-deficient mouse sperm were capable of dispersing cumulus cells from the cumulus mass. Cumulus cell dispersal was strongly inhibited by the presence of a hyaluronidase inhibitor, apigenin. These results suggest that in the mouse, Hyal5 may function principally as a “cumulus matrix depolymerase” in the sperm penetration through the cumulus mass and in the local hyaluronan hydrolysis near or on the surface of the egg zona pellucida to enable the proximal region of sperm tail to move freely. PH-20 may compensate in part for the functional roles of Hyal5.
129 citations
TL;DR: It is proved that 2 protein bands of approximately 14 (P14) and 20 (P20) kd isolated from seminal plasma are responsible for this protective effect and suggest that both proteins are involved in sperm CA and gamete interaction, first by stabilizing the sperm membrane and then by participating in CA in the female reproductive tract.
Abstract: We have already shown that seminal plasma proteins in the ram can repair cold-shock sperm membrane damage and that the addition of seminal plasma proteins before cold-shock treatment prevents sperm membrane injury. In this study, we prove that 2 protein bands of approximately 14 (P14) and 20 (P20) kd isolated from seminal plasma are responsible for this protective effect. In vitro capacitation (CA) and acrosome reaction (AR) modified the content of both proteins on the sperm surface. P20 release began at the beginning of CA, and the induction of the AR accounted for an additional release of both proteins; not more than 35% of these proteins remained on acrosome-reacted sperm. Cytochemical analysis detected that there are several binding sites for P14 and P20 on the sperm surface and that membrane alterations induced by CA and the AR accounted for the loss and redistribution of both proteins to the equatorial and postequatorial regions. The P14-sequenced fragment showed a high homology with several seminal plasma proteins of different species and contained the FN 2 domain like bovine PDC-109. However, the sequence of the P20 fragment was not homologous with any reported protein. By immunochemical analysis, we obtained evidence that P14 is phosphorylated in serine and threonine residues and that P20 is a glycosylated protein. These results suggest that both proteins are involved in sperm CA and gamete interaction, first by stabilizing the sperm membrane and then by participating in CA in the female reproductive tract. The protective effect of P14 and P20 could be related to their decapacitating role.
110 citations
TL;DR: The results suggest that PS exposure in human sperm, as induced by A23187, is mainly related to the acrosome reaction rather than to apoptosis.
Abstract: BACKGROUND: Translocation of phosphatidylserine (PS) from the inner to the outer leaflet of the plasma membrane is a modification of the lipid architecture occurring in sperm. This is one of the earliest signs of apoptosis that can be monitored by the calcium-dependent binding of annexin V. METHODS AND RESULTS: Flow cytometric analysis of annexin V binding was performed. Calcium ionophore A23187 led to a significant increase in the proportion of living sperm with PS exposure: 7.3 ± 3.2% of cells in the untreated ejaculate versus 47.5 ± 5.6% of cells after 1 h of incubation with A23187. Conversely, diminution of mitochondrial membrane potential [DiOC 6 (3)/propidium iodide (PI) assay], caspase activation [fluorescein isothiocyanate (FITC)-Val-Ala-Asp-fluoromethylketone (VAD-FMK)/PI assay], increased plasma membrane permeability (Yo-Pro-1/PI assay) and increased DNA fragmentation [TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end labelling assay], which are among the main signs of apoptosis, were not observed in sperm, even after 4 h of incubation with A23187. However, A23187 significantly increased the proportion of sperm with plasma membrane scrambling and with a reacted acrosome, as detected with the merocyanine 540 probe (M540) and the monoclonal anti-human CD46-PE antibody respectively. CONCLUSIONS: Our results suggest that PS exposure in human sperm, as induced by A23187, is mainly related to the acrosome reaction rather than to apoptosis.
104 citations
TL;DR: The main findings emerging from this study were that the addition of GSH to the freezing media resulted in an improvement in percent motility and motion parameters of thawed spermatozoa, as measured by both microscopic analysis and computer-assisted semen analysis (CASA).
Abstract: In this study, we evaluated the effects of glutathione (L-gamma-glutamyl-L-cysteinylglycine; GSH) supplementation of the freezing extender on semen parameters during the cooling (2 hours at 5 degrees C) and freezing phases of the cryopreservation process to compensate for the decrease in GSH content observed during sperm freezing. To fully address these questions, we incorporated a new set of functional sperm tests. These included tests of mitochondrial function, inducibility of the acrosome reaction, in vitro penetration (IVP) of oocytes, changes in sulfhydryl group content in membrane proteins, and capacitation status. The main findings emerging from this study were that the addition of GSH to the freezing media resulted in 1) an improvement in percent motility (%MOT) and motion parameters of thawed spermatozoa, as measured by both microscopic analysis and computer-assisted semen analysis (CASA); 2) a higher number of total viable spermatozoa; 3) a higher number of noncapacitated viable spermatozoa; and 4) a decrease in the number of spermatozoa with changes in the sulfhydryl groups in membrane proteins. This protective effect on sperm function was more pronounced with 1 mM of GSH than with 5 mM of GSH.
97 citations
TL;DR: Investigation of the expression of HSPD1 and TRA1 during the ontogeny of male germ cells through spermatogenesis, epididymal sperm maturation, capacitation, and acrosomal exocytosis reinforces the notion that these chaperones are intimately involved in the mechanisms by which mammalian spermatozoa both acquire and express their ability to recognize the zona pellucida.
Abstract: Although the molecular basis of sperm-oocyte interaction is unclear, recent studies have implicated two chaperone proteins, heat shock protein 1 (HSPD1; previously known as heat shock protein 60) and tumor rejection antigen gp96 (TRA1; previously known as endoplasmin), in the formation of a functional zonareceptor complex on the surface of mammalian spermatozoa. The current study was undertaken to investigate the expression of these chaperones during the ontogeny of male germ cells through spermatogenesis, epididymal sperm maturation, capacitation, and acrosomal exocytosis. In testicular sections, both HSPD1 and TRA1 were closely associated with the mitochondria of spermatogonia and primary spermatocytes. However, this labeling pattern disappeared from the male germ line during spermiogenesis to become undetectable in testicular spermatozoa. Subsequently, these chaperones could be detected in epididymal spermatozoa and in previously unreported ‘‘dense bodies’’ in the epididymal lumen. The latter appeared in the precise region of the epididymis (proximal corpus), where spermatozoa acquire the capacity to recognize and bind to the zona pellucida, implicating these structures in the functional remodeling of the sperm surface during epididymal maturation. Both HSPD1 and TRA1 were subsequently found to become coexpressed on the surface of live mouse spermatozoa following capacitation in vitro and were lost once these cells had undergone the acrosome reaction, as would be expected of cell surface molecules involved in sperm-egg interaction. These data reinforce the notion that these chaperones are intimately involved in the mechanisms by which mammalian spermatozoa both acquire and express their ability to recognize the zona pellucida.
95 citations
TL;DR: The retention of mouse sperm lysozyme-like protein (mSLLP1) in the equatorial segment of spermatozoa following the acrosome reaction and a role for mSollP1 in sperm-egg binding and fertilization are demonstrated and the hypothesis that a c lyso enzyme-likeprotein is involved in the binding of spermutozoa to the egg plasma membrane during fertilization is supported.
TL;DR: Although substantial improvements have been made in canine semen assessment, surprisingly few parameters were correlated with in vivo fertility, therefore, further research is required to determine which sperm characteristics are of clinical value for predicting the in vivoertility in dogs.
TL;DR: This report is the first to demonstrate the presence of CaMKIV in mammalian sperm and suggests the involvement of this kinase in the regulation of human sperm motility.
Abstract: The mechanisms involved in the regulation of mammalian sperm motility are not well understood. Calcium ions (Ca(2+)) have been suggested to play a key role in the maintenance of motility; nevertheless, how Ca(2+) modulates this process has not yet been completely characterized. Ca(2+) can bind to calmodulin and this complex regulates the activity of multiple enzymes, including Ca(2+)/calmodulin-dependent protein kinases (CaM kinases). Results from this study confirmed that the presence of Ca(2+) in the incubation medium is essential for maintaining human sperm motility. The involvement of CaM kinases in Ca(2+) regulation of human sperm motility was evaluated using specific inhibitors (KN62 and KN93) or their inactive analogues (KN04 and KN92 respectively). Sperm incubation in the presence of KN62 or KN93 led to a progressive decrease in the percentage of motile cells; in particular, incubation with KN62 also reduced sperm motility parameters. These inhibitors did not alter sperm viability, protein tyrosine phosphorylation or the follicular fluid-induced acrosome reaction; however, KN62 decreased the total amount of ATP in human sperm. Immunological studies showed that Ca(2+)/calmodulin-dependent protein kinase IV (CaMKIV) is present and localizes to the human sperm flagellum. Moreover, CaMKIV activity increases during capacitation and is inhibited in the presence of KN62. This report is the first to demonstrate the presence of CaMKIV in mammalian sperm and suggests the involvement of this kinase in the regulation of human sperm motility.
TL;DR: The overall data demonstrate that Hsp70 is present on boar sperm with a dynamic redistribution as the sperm undergoes capacitation and acrosome reaction and suggest an important role of this protein during porcine gamete interaction.
Abstract: The presence and cellular distribution of heat protein 70 (Hsp70) in ejaculated, capacitated, and acrosome-reacted boar spermatozoa was evaluated by immunofluorescence and Western blot; the role of Hsp70 during fertilization was also studied. In freshly ejaculated spermatozoa, Hsp70 immunoreactivity is present in a well-defined triangular-shaped area in the equatorial segment that seems to correspond to the equatorial sub-segment. The distribution of the fluorescent signal changes in capacitated sperm, that exhibit different patterns probably in relation to the stage of capacitation of individual cells; after acrosome reaction Hsp70 immunoreactivity is localized on both a thick sub-equatorial band and a triangle in the equatorial segment. In reacted spermatozoa, Hsp70 seems to be not only relocalized but also translocated from the inner to the outer leaflet of the sperm plasma membrane, as a significant (P < 0.05) increase in the proportion of unfixed cells showing the fluorescent signal has been recorded. No differences in Hsp70 amount between fresh, capacitated, and reacted semen were observed by Western blot. The presence of anti-Hsp70 antibody in the fertilization medium significantly reduced, in a concentration-dependent manner, the fertilization rate of both zona-intact and zona-free oocytes. The overall data demonstrate that Hsp70 is present on boar sperm with a dynamic redistribution as the sperm undergoes capacitation and acrosome reaction and suggest an important role of this protein during porcine gamete interaction.
TL;DR: Results indicate that sea urchin eggs may release AEA after activation by the fertilizing sperm, and suggest that AEA signaling directly affects sperm functions required for fertilization and provide additional evidence for common signaling processes in neurons and sperm.
Abstract: Sea urchin and human sperm contain receptors for neurotransmitters and psychoactive drugs, including cannabinoid receptors (CNRs). Anandamide, arachidonoylethanolamide (AEA), is a lipid-signal molecule that is an endogenous agonist for CNRs. AEA is enyzmatically released from membrane phospholipids when neurons are stimulated. Retrograde AEA signals from depolarized postsynaptic neurons inhibit neurotransmitter release at synapses in mammalian brain. Analogous processes regulate sperm functions during fertilization in sea urchins. AEA and (−)Δ9tetrahydrocannabinol [(−)Δ9THC], the major psychoactive constituent of marijuana, inhibit fertilization by blocking acrosomal exocytosis/acrosome reactions (AR) stimulated by egg jelly. The acrosome is a Golgi-derived secretory granule in sperm analogous to synaptic vesicles in neurons. AEA and (−)Δ9THC do not block ionophore-induced AR, suggesting that they inhibit AR by modulating signal transduction event(s) before opening of ion channels. Unfertilized s...
TL;DR: Results indicate that human TPX1 would be a component of the sperm acrosome that remains associated with sperm after capacitation and AR, and is relevant for sperm-oocyte interaction.
Abstract: Testicular protein Tpx-1, also known as CRISP-2, is a cysteine-rich secretory protein specifically expressed in the male reproductive tract. Since the information available on the human protein is limited to the identification and expression of its gene, in this work we have studied the presence and localization of human Tpx-1 (TPX1) in sperm, its fate after capacitation and acrosome reaction (AR), and its possible involvement in gamete interaction. Indirect immunofluorescence studies revealed the absence of significant staining in live or fixed non-permeabilized sperm, in contrast to a clear labelling in the acrosomal region of permeabilized sperm. These results, together with complementary evidence from protein extraction procedures strongly support that TPX1 would be mainly an intra-acrosomal protein in fresh sperm. After in vitro capacitation and ionophore-induced AR, TPX1 remained associated with the equatorial segment of the acrosome. The lack of differences in the electrophoretic mobility of TPX1 before and after capacitation and AR indicates that the protein would not undergo proteolytical modifications during these processes. The possible involvement of TPX1 in gamete interaction was evaluated by the hamster oocyte penetration test. The presence of anti-TPX1 during gamete co-incubation produced a significant and dose-dependent inhibition in the percentage of penetrated zona-free hamster oocytes without affecting sperm motility, the AR or sperm binding to the oolema. Together, these results indicate that human TPX1 would be a component of the sperm acrosome that remains associated with sperm after capacitation and AR, and is relevant for sperm-oocyte interaction.
TL;DR: It is demonstrated that sp32, a (pro)acrosin binding protein, is the p 32, a tyrosine phosphorylated protein related to capacitation, a protein implicated in proacros in maturation.
Abstract: Mammalian sperm must undergo capacitation, a preparation period in the female reproductive tract or in vitro, in order to fertilize. We have previously described a Mr 32 000 tyrosine phosphorylated protein, "p32," that appears in pig sperm during capacitation. The identity of p32 remains unknown; if and how it is involved during capacitation is not understood. The objective of the present study was to identify p32 by proteomic techniques. Western blotting of proteins separated successively under nonreducing and then reducing conditions showed the appearance of the tyrosine phosphorylated p32 only when sperm were incubated in capacitating conditions. The spot was sequenced by mass spectrometry/mass spectrometry and identified as "sp32," a protein implicated in proacrosin maturation. The same membranes probed with anti-sp32 antibody demonstrated that sp32 is present in both noncapacitating and capacitating conditions and revealed exactly the same spot as p32. Immunoprecipitation with either anti-phosphotyrosine or anti-sp32 antibody corroborated these results. Indirect immunofluorescence with anti-phosphotyrosine antibody or anti-sp32 antibody show similar labeling of capacitated sperm, supporting the hypothesis that p32 is a tyrosine phosphorylated form of sp32. After ionophore treatment to induce the acrosome reaction, anti-sp32 and anti-phosphotyrosine labeling on the acrosome disappeared. These results demonstrate that sp32, a (pro)acrosin binding protein, is the p32, a tyrosine phosphorylated protein related to capacitation. We will now focus on the significance of tyrosine phosphorylation on sp32 function during fertilization-related events.
TL;DR: The observations indicated that the sperm head cortical cytoskeleton exhibits significant changes during the acrosome reaction and, therefore, support the image of cytoskeletal proteins as highly dynamic structures participating actively in processes prior to fertilization.
Abstract: Three major cytoskeletal proteins, actin, tubulin and spectrin, are present in the head of mammalian spermatozoa. Although cytoskeletal proteins are implicated in the regulation of capacitation and the acrosome reaction (AR), their exact role remains poorly understood. The aim of this study was to compare the distribution of the sperm head cytoskeleton before and after the AR in spermatozoa representing a range of acrosome size and shape. Spermatozoa from the human and three rodents (rat, hamster and grey squirrel) were fixed before and after the AR in appropriate medium in vitro. Indirect immunofluorescent localization of cytoskeletal proteins was undertaken with antibodies recognizing actin, spectrin and a-tubulin. Preparations were counterstained with propidium iodide and examined by epifluorescent and confocal microscopy. Our results clearly demonstrated changes in localization of cytoskeleton during the AR, mainly in the apical acrosome with further changes to the equatorial segment and post-acrosomal regions. The pattern of cytoskeletal proteins in the sperm head of all the species was similar in respect to various sub-compartments. These observations indicated that the sperm head cortical cytoskeleton exhibits significant changes during the AR and, therefore, support the image of cytoskeletal proteins as highly dynamic structures participating actively in processes prior to fertilization.
TL;DR: It is found that electroejaculation resulted in a lower recovery efficiency (80% of the cases), as a consequence of contamination with urine or lack of response to the electrical stimulation, and the fresh seminal quality was not significantly different between recovery methods.
TL;DR: The presence in human sperm of α7, α9, α3, α5, and β4 nicotinic acetylcholine receptor subunits and the following proteins known to be associated with the receptor in the somatic cell: rapsyn and the tyrosine kinases c-SRC and FYN are reported.
TL;DR: A review compiles the major observations on the forms of the progesterone receptor in various reproductive tissues to indicate that PR can serve as the marker to define the fertilizing potential of the spermatozoa.
Abstract: The unequivocal role of progesterone in a variety of events like ovulation, mammary gland development, establishment and maintenance of pregnancy etc are well established. Also the data are accumulating on its role in male reproductive events. In vertebrates and humans, the biological activity of progesterone is mediated by two progesterone receptor proteins PR-A and PR-B, that arise from the same gene and are the members of nuclear receptor superfamily of transcriptional factors. Several studies have demonstrated that the blockage of progesterone receptor using antiprogestins impairs folliculogenesis, ovulation, implantation and pregnancy. Progesterone receptor (PR), have also been detected in human spermatozoa. However, unlike the conventional PR, sperm PR was localized on the membrane and showed distinct characteristics in terms of its size. There are data to demonstrate the inhibition of progesterone driven functions such as hyperactive motility, acrosome reaction on neutralization of sperm membrane PR with specific antibodies against PR. Further significant decrease in the % of PR positive spermatozoa was observed in infertile cases as compared to the fertile men. This indicated that PR can serve as the marker to define the fertilizing potential of the spermatozoa. Recently we have also shown that the PR is expressed in human testis. This reinforced that this PR protein is an inherent testicular protein and not a secretion of accessory reproductive organs. This review compiles the major observations on the forms of the progesterone receptor in various reproductive tissues.
TL;DR: It can be concluded that the simultaneous use of the sperm membrane responsiveness and kinetic parameters is a sensitive tool for the detection of storage-related membrane changes in boar semen.
TL;DR: Application of recombinant DNA, transgenic and gene targeting technology to issues in mammalian fertilization has revolutionized the field and new information and new insights have come from relatively recent investigations.
TL;DR: It is argued that results of these transgenic experiments actually are consistent with the prevailing view of gamete recognition that implicates a specific ZP glycoprotein in both binding of mouse sperm to eggs and induction of the acrosome reaction.
Abstract: For sperm to fertilize eggs, they must first bind to the thick zona pellucida (ZP) that surrounds the plasma membrane of all unfertilized mammalian eggs. An extensive literature suggests that mouse sperm recognize and bind to a specific ZP glycoprotein called mZP3. However, the role of individual ZP glycoproteins in binding of mouse sperm to eggs has been called into question by recent transgenic experiments with null mice. Results of such experiments have been interpreted to mean that binding of sperm depends on the supramolecular structure of the ZP, not on an individual ZP glycoprotein. Here, it is argued that results of these transgenic experiments actually are consistent with the prevailing view of gamete recognition that implicates a specific ZP glycoprotein in both binding of mouse sperm to eggs and induction of the acrosome reaction. © 2005 Wiley-Liss, Inc.
TL;DR: A key role for alpha-SNAP/NSF in the AR is suggested, and the understanding of the molecular players involved in the vesicle-to-plasma membrane fusion taking place during exocytosis is strengthened.
Abstract: The acrosome is a membrane-limited granule that overlies the nucleus of the mature spermatozoon. In response to physiological or pharmacological stimuli it undergoes a special type of Ca2+-dependent exocytosis termed the acrosome reaction (AR), which is an absolute prerequisite for fertilization. Aided by a streptolysin-O permeabilization protocol developed in our laboratory, we have previously demonstrated requirements for Rab3A, N-ethylmaleimide-sensitive factor (NSF), several soluble NSF-attachment protein receptor (SNARE) proteins, and synaptotagmin VI in the human sperm AR. Here, we show that alpha-soluble NSF-attachment protein (alpha-SNAP), a protein essential for most fusion events through its interaction with NSF and the SNARE complex, exhibits a direct role in the AR. First, the presence of alpha-SNAP is demonstrated by the Western blot of human sperm protein extracts. Immunostaining experiments reveal an acrosomal localization for this protein. Second, the Ca2+ and Rab3A-triggered ARs are inhibited by anti-alpha-SNAP antibodies. Third, bacterially expressed alpha-SNAP abolishes exocytosis in a fashion that depends on its interaction with NSF. Fourth, we show a requirement for alpha-SNAP/NSF in a prefusion step early in the exocytotic pathway, after the tethering of the acrosome to the plasma membrane and before the efflux of intra-acrosomal Ca2+. These results suggest a key role for alpha-SNAP/NSF in the AR, and strengthen our understanding of the molecular players involved in the vesicle-to-plasma membrane fusion taking place during exocytosis.
TL;DR: It is demonstrated that junctate is expressed in sperm and co-localizes with the IP3R in the acrosomal crescent of the anterior head of rodent sperm, which provides a new hypothesis concerning sperm TRPC2 gating:TRPC2 activation may be due to modifications of its interaction with both junctates and IP3r, induced by depletion of calcium from the Acrosomal vesicle.
TL;DR: Protein analysis revealed that ADAM7, but not ADAM28, is transferred from the epididymis to the sperm surface and redistributed in the sperm head during acrosome reaction and these processes were shown to occur without processing of the protein.
TL;DR: These studies, for the first time, have demonstrated that in humans, ZPB also induces acrosomal exocytosis through a Gi independent pathway.
Abstract: To facilitate our understanding of the role of zona pellucida glycoproteins during fertilization in humans, recombinant human zona pellucida glycoprotein-A (hZPA), -B (hZPB) and -C (hZPC) were obtained by using Escherichia coli and baculovirus expression systems. Analysis by SDS-PAGE and Western blot of the Ni-NTA affinity purified recombinant proteins revealed that the baculovirus-expressed hZPA, hZPB and hZPC have an apparent molecular weight of ,110, ,70‐75 and ,65kDa, respectively, as compared to ,80, ,65 and ,50kDa of the respective E. coli-expressed proteins. Lectin binding studies revealed that the baculovirus-expressed recombinant zona proteins were glycosylated. Major oligosaccharides were represented by strong reactivity with Concanavalin A (mannose a 1‐3 or mannose a 1‐6 residues) and Jacalin (a-O glycosides of Gal or GalNAc moieties). A significant increase in acrosomal exocytosis was observed when capacitated human sperm were incubated in vitro with baculovirus-expressed hZPB (P 5 0.0005) and hZPC (P 5 0.0005) The E. coli-expressed hZPB, hZPC and baculovirus-expressed hZPA failed to induce any significant increase ( P> 0.05) in acrosome reaction. In contrast to hZPC, the acrosome reaction induced by recombinant hZPB was not inhibited by pertussis toxin. These studies, for the first time, have demonstrated that in humans, ZPB also induces acrosomal exocytosis through a Gi independent pathway.
TL;DR: It is shown that short incubations with cyclodextrin, a cholesterol removal agent, just before stimulation promote acrosomal exocytosis, and cholesterol efflux facilitates Rab3A association to sperm plasma membrane, indicating that cholesterol plays a direct role in the calcium-dependent exocyTosis associated with acrosome reaction.
TL;DR: Evidence that cigarette smoking affects male fertility via altering the sperm quality is provided, indicating removal of SM's SP and then subsequent reconstitution with physiological media could be of clinical significance in the various assisted reproductive technologies applied for SM.
Abstract: Numerous investigations have been conducted on the relationship between cigarette smoking and male infertility, however, the exact molecular mechanisms are not well understood in most of the cases. Few studies have indicated the direct effect of seminal plasma (SP) [in different dilutions with phosphate buffer solution (PBS)] from smokers (SM) on the sperm functional parameters from nonsmokers (non-SM). The aim of this study was to provide evidence that cigarette smoking affects male fertility via altering the sperm quality. Our results indicated that exposure of spermatozoa from the non-SM to the SP from the SM yielded a significant reduction in the sperm motility and acrosome reaction and an elevation in the amount of malondialdehyde (MDA), in a certain time course. Exposure of spermatozoa from the SM to the SP from the non-SM or with PBS resulted in the nonsignificant improvement in the altered sperm functional parameters indicating removal of SM's SP and then subsequent reconstitution with physiological media could be of clinical significance in the various assisted reproductive technologies applied for SM. However, the detrimental effect of SM's SP on non-SM's spermatozoa was prominent. In addition, as spermatozoa in SM's SP are susceptible to peroxidative damages, men with such cells who wish to have children should especially benefit from quitting smoking.