Efficacy and safety of 2 risperidone doses were evaluated in children and adolescents with autism. Patients (N = 96; 5–17 years), received risperidone (low-dose: 0.125 mg/day [20 to <45 kg], 0.175 mg/day [>45 kg] or high-dose: 1.25 mg/day [20 to <45 kg], 1.75 mg/day [>45 kg]) or placebo. Mean baseline (range 27–29) to endpoint change in Aberrant Behavior Checklist-Irritability (primary endpoint) was significantly greater in the high-dose—(−12.4 [6.5]; p < 0.001), but not low-dose (−7.4 [8.1]; p = 0.164) group, versus placebo (−3.5 [10.7]). Clinical Global Impressions-Severity and Children’s Yale-Brown Obsessive Compulsive Scale scores improved significantly only in the high-dose group, consistent with ABC-I results. Somnolence, sedation and increased appetite occurred more frequently in high-versus low-dose groups. Overall, increased appetite occurred most frequently.

This open-label, rater-blinded, parallel-group study was designed to evaluate noninferiority of paliperidone palmitate (PP), a once-monthly injectable atypical antipsychotic, to once-biweekly risperidone long-acting injectable (RIS-LAI) in adult Chinese patients with acute schizophrenia. Eligible Chinese adults (N=452) with schizophrenia were randomized (1:1) to either PP (N=229; deltoid injections on day 1 [150mg eq.] and day 8 [100mg eq.]; then once-monthly deltoid or gluteal injections, flexibly dosed [50, 100, or 150mg eq.]), or RIS-LAI (N=223; once-biweekly gluteal injections, flexibly dosed [25, 37.5 or 50mg]). RIS-LAI-treated patients received oral risperidone supplementation (1-6mg/day) at initiation and with RIS-LAI dose increases. Mean (SD) Positive and Negative Syndrome Scale (PANSS) total score at baseline was 83.2 (12.44). Mean (SD) change from baseline to endpoint in PANSS total scores (primary efficacy measure) was: −23.6 (16.28) for PP group and −26.9 (15.43) for RIS-LAI group. PP was noninferior to RIS-LAI (least squares mean difference [95% CI]: −2.3 [−5.20; 0.63]; predetermined non-inferiority margin: −5.5). Mean (SD) change from baseline to endpoint in Clinical Global Impression-Severity scale score was: −1.5 (1.24; PP group), −1.7 (1.16; RIS-LAI group) and in Personal and Social Performance Scale scores was: 16.8 (14.76; PP group), 18.6 (13.92; RIS-LAI group). The incidence of treatment-emergent adverse events (TEAEs) was similar between the two groups (73% [PP]; 75% [RIS-LAI]). The most common TEAEs were akathisia, tremor, and insomnia. The study demonstrated the noninferiority of PP (50–150mg eq., flexibly dosed, without oral paliperidone supplementation) to risperidone-LAI (25–50mg, flexibly dosed, with oral risperidone supplementation) for the treatment of acute schizophrenia in adult Chinese patients. PP injections were generally tolerable, and no new safety signals were detected in this population.

Using a focused screen of biogenic amine compounds we identified a novel series of H(3)R antagonists. A preliminary SAR study led to reduction of MW while increasing binding affinity and potency. Optimization of the physical properties of the series led to (S)-6n, with improved brain to plasma exposure and efficacy in both water intake and novel object recognition models.

Sperm capacitation in vitro is highly correlated with an increase in protein tyrosine phosphorylation that is regulated by cAMP through a unique mode of signal transduction cross-talk. The activation of this signaling pathway, as well as capacitation, requires bovine serum albumin (BSA) in the incubation medium. BSA is hypothesized to modulate capacitation through its ability to remove cholesterol from the sperm plasma membrane. Here we demonstrate that the cholesterol-binding heptasaccharides, methyl-beta-cyclodextrin and OH-propyl-beta-cyclodextrin, promote the release of cholesterol from the mouse sperm plasma membrane in media devoid of BSA. Both of these beta-cyclodextrins were also demonstrated to increase protein tyrosine phosphorylation in the absence of BSA in both mouse and bull sperm, and the patterns of phosphorylation were similar to those induced by media containing BSA. The potency of the different beta-cyclodextrins to increase protein tyrosine phosphorylation in sperm was correlated with their cholesterol binding efficiencies, and preincubation of the beta-cyclodextrins with cholesterol-SO4- to saturate their cholesterol-binding sites blocked the ability of these compounds to stimulate protein tyrosine phosphorylation. The beta-cyclodextrin effect on protein tyrosine phosphorylation was both NaHCO3 and protein kinase A-dependent. The beta-cyclodextrins were also able to capacitate mouse sperm in the absence of BSA, as measured by the ability of the zona pellucida to induce the acrosome reaction and by successful fertilization in vitro. In summary, beta-cyclodextrins can completely replace BSA in media to support signal transduction leading to capacitation. These data further support the coupling of cholesterol efflux to the activation of membrane and transmembrane signaling events leading to the activation of a unique signaling pathway involving the cross-talk between cAMP and tyrosine kinase second messenger systems, thus defining a new mode of cellular signal transduction initiated by cholesterol release.

Sperm capacitation in vitro is highly correlated with an increase in protein tyrosine phosphorylation that is regulated by cAMP through a unique mode of signal transduction cross-talk. The activation of this signaling pathway, as well as capacitation, requires bovine serum albumin (BSA) in the incubation medium. BSA is hypothesized to modulate capacitation through its ability to remove cholesterol from the sperm plasma membrane. Here we demonstrate that the cholesterol-binding heptasaccharides, methyl-β-cyclodextrin and OH-propyl-β-cyclodextrin, promote the release of cholesterol from the mouse sperm plasma membrane in media devoid of BSA. Both of these β-cyclodextrins were also demonstrated to increase protein tyrosine phosphorylation in the absence of BSA in both mouse and bull sperm, and the patterns of phosphorylation were similar to those induced by media containing BSA. The potency of the different β-cyclodextrins to increase protein tyrosine phosphorylation in sperm was correlated with their cholesterol binding efficiencies, and preincubation of the β-cyclodextrins with cholesterol- SO4 − to saturate their cholesterol-binding sites blocked the ability of these compounds to stimulate protein tyrosine phosphorylation. The β-cyclodextrin effect on protein tyrosine phosphorylation was both NaHCO3 and protein kinase A-dependent. The β-cyclodextrins were also able to capacitate mouse sperm in the absence of BSA, as measured by the ability of the zona pellucida to induce the acrosome reaction and by successful fertilization in vitro. In summary, β-cyclodextrins can completely replace BSA in media to support signal transduction leading to capacitation. These data further support the coupling of cholesterol efflux to the activation of membrane and transmembrane signaling events leading to the activation of a unique signaling pathway involving the cross-talk between cAMP and tyrosine kinase second messenger systems, thus defining a new mode of cellular signal transduction initiated by cholesterol release.

We previously demonstrated that mouse sperm capacitation is accompanied by a time-dependent increase in protein tyrosine phosphorylation that is dependent on the presence of BSA, Ca2+, and NaHCO(3), all three of which are also required for this maturational event. We also demonstrated that activation of protein kinase A (PK-A) is upstream of this capacitation-associated increase in protein tyrosine phosphorylation. BSA is hypothesized to modulate capacitation through the removal of cholesterol from the sperm plasma membrane. In this report, we demonstrate that incubation of mouse sperm medium containing BSA results in a release of cholesterol from the sperm plasma membrane to the medium; release of this sterol does not occur in medium devoid of BSA. We next determined whether cholesterol release leads to changes in protein tyrosine phosphorylation. Blocking the action of BSA by adding exogenous cholesterol-SO-(4) to the BSA-containing medium inhibits the increase in protein tyrosine phosphorylation as well as capacitation. This inhibitory effect is overcome by (1) the addition of increasing concentrations of BSA at a given concentration of cholesterol-SO-(4) and (2) the addition of dibutyryl cAMP plus IBMX. High-density lipoprotein (HDL), another cholesterol binding protein, also supports the capacitation-associated increase in protein tyrosine phosphorylation through a cAMP-dependent pathway, whereas proteins that do not interact with cholesterol have no effect. HDL also supports sperm capacitation, as assessed by fertilization in vitro. Finally, we previously demonstrated that HCO-(3) is necessary for the capacitation-associated increase in protein tyrosine phosphorylation and demonstrate here, by examining the effectiveness of HCO-(3) or BSA addition to sperm on protein tyrosine phosphorylation, that the HCO-(3) effect is downstream of the site of BSA action. Taken together, these data demonstrate that cholesterol release is associated with the activation of a transmembrane signal transduction pathway involving PK-A and protein tyrosine phosphorylation, leading to functional maturation of the sperm.

Journal of AndrologyVolume 19, Issue 2 p. 242-248 Free Access The Molecular Basis of Sperm Capacitation PABLO E. VISCONTI, PABLO E. VISCONTI Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania.Search for more papers by this authorHANNAH GALANTINO-HOMER, HANNAH GALANTINO-HOMER Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania.Search for more papers by this authorGRACE D. MOORE, GRACE D. MOORE Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania. Department of Pathology, Allegheny University Hospitals, Philadelphia, Pennsylvania.Search for more papers by this authorJANICE L. BAILEY, JANICE L. BAILEY Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania. Centre de Recherche en Biologie de la Reproduction, Department des Sciences Animales, Universite Laval, Quebec, Quebec, Canada.Search for more papers by this authorXIAOPING NING, XIAOPING NING Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania. Wyeth Ayerst Laboratories, Princeton, New Jersey.Search for more papers by this authorMIGUEL FORNES, MIGUEL FORNES Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania. Institute de Histologia y Embriologica, Facultad de Ciencias, Medicas Universidad Nacional de Cuyo, Casilla de Correo 56, Mendoza 5500, Argentina.Search for more papers by this authorGREGORY S. KOPF Ph.D., Corresponding Author GREGORY S. KOPF Ph.D. Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania.Center for Research on Reproduction and Women's Health, Room 313, John Morgan Building, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104–6080.Search for more papers by this author PABLO E. VISCONTI, PABLO E. VISCONTI Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania.Search for more papers by this authorHANNAH GALANTINO-HOMER, HANNAH GALANTINO-HOMER Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania.Search for more papers by this authorGRACE D. MOORE, GRACE D. MOORE Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania. Department of Pathology, Allegheny University Hospitals, Philadelphia, Pennsylvania.Search for more papers by this authorJANICE L. BAILEY, JANICE L. BAILEY Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania. Centre de Recherche en Biologie de la Reproduction, Department des Sciences Animales, Universite Laval, Quebec, Quebec, Canada.Search for more papers by this authorXIAOPING NING, XIAOPING NING Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania. Wyeth Ayerst Laboratories, Princeton, New Jersey.Search for more papers by this authorMIGUEL FORNES, MIGUEL FORNES Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania. Institute de Histologia y Embriologica, Facultad de Ciencias, Medicas Universidad Nacional de Cuyo, Casilla de Correo 56, Mendoza 5500, Argentina.Search for more papers by this authorGREGORY S. KOPF Ph.D., Corresponding Author GREGORY S. KOPF Ph.D. Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania.Center for Research on Reproduction and Women's Health, Room 313, John Morgan Building, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104–6080.Search for more papers by this author First published: 02 January 2013 https://doi.org/10.1002/j.1939-4640.1998.tb01994.xCitations: 46 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat References Aitken RJ, Paterson M., Fisher H., Buckingham DW, Van Duin M. Redox regulation of tyrosine phosphorylation in human spermatozoa and its role in the control of human sperm function. J Cell Sci 1995; 108: 2017–2025. Arnoult C., Zeng Y., Florman HM. ZP3-dependent activation of sperm cation channels regulates acrosomal secretion during mammalian fertilization. J Cell Biol 1996; 134: 637–645. Austin CR. Observations on the penetration of the sperm into the mammalian egg. Aust J Sci Res 1951; 4: 581–596. Austin CR. The “capacitation” of the mammalian sperm. Nature 1952; 170: 326. Boatman DE, Robbins RS. Bicarbonate: carbon-dioxide regulation of sperm capacitation, hyperactivated motility, and acrosome reactions. Biol Reprod 1991; 44: 806–813. Carrera A., Moos J., Ning XP, Gerton GL, Tesarik J., Kopf GS, Moss SB. Regulation of protein tyrosine phosphorylation in human sperm by a calcium/calmodulin-dependent mechanism: identification of A kinase anchor proteins as major substrates for tyrosine phosphorylation. Dev Biol 1996; 180: 284–296. Chang MC. Fertilizing capacity of spermatozoa deposited into the fallopian tubes. Nature 1951; 168: 697–698. Chang MC. Development of fertilizing capacity of rabbit spermatozoa in the uterus. Nature 1955; 175: 1036–1037. Cohen-Dayag A., Eisenbach M. Potential assays for sperm capacitation in mammals. Am J Physiol Cell Physiol 1994; 267: C1167–C1176. Cross NL. Role of cholesterol in sperm capacitation. Biol Reprod 1998; in press. DasGupta S., Mills CL, Fraser LR. Ca2+-related changes in the capacitation state of human spermatozoa assessed by a chlortetracycline fluorescence assay. J Reprod Fertil 1993; 99: 135–143. de Lamirande E., Gagnon C. A positive role for the superoxide anion in triggering hyperactivation and capacitation of human spermatozoa. Int J Androl 1993; 16: 21–25. Emiliozzi C., Fenichel P. Protein tyrosine phosphorylation is associated with capacitation of human sperm in vitro but is not sufficient for its completion. Biol Reprod 1997; 56: 674–679. Florman HM, Babcock DF. Progress towards understanding the molecular basis of capacitation. In: P. Wassarman, ed. Elements of Mammalian Fertilization. Vol. I. Basic Concepts. Boca Raton, Florida: CRC Press; 1991: 105–132. Florman HM, Lemos JR, Arnoult C., Kazam I., O'Toole C. Sperm ion channel regulation during capacitation and fertilization. Biol Reprod 1998; in press. Fraser LR, Herod JE. Expression of capacitation-dependent changes in chlortetracycline fluorescence patterns in mouse spermatozoa requires a suitable glycolysable substrate. J Reprod Fertil 1990; 88: 611–621. Galantino-Homer H., Visconti PE, Kopf GS. Regulation of protein tyrosine phosphorylation during bovine sperm capacitation by a cyclic adenosine 3′,5′-monophosphate-dependent pathway. Biol Reprod 1997; 56: 707–719. Garty N., Salomon Y. Stimulation of partially purified adenylate cyclase from bull sperm by bicarbonate. FEBS Lett 1987; 218: 148–152. Go KJ, Wolf DP. Albumin-mediated changes in sperm sterol content during capacitation. Biol Reprod 1985; 32: 145–153. Harrison RAP. Capacitation mechanisms, and the role of capacitation as seen in eutherian mammals. Reprod Fertil Dev 1996; 8: 581–594. Hunter AG, Nornes HO. Characterization and isolation of a sperm-coating antigen from rabbit seminal plasma with capacity to block fertilization. J Reprod Fertil 1969; 20: 419–427. Hyne RV, Garbers DL. Regulation of guinea pig sperm adenylate cyclase by calcium. Biol Reprod 1979; 21: 1135–1142. Langlais J., Roberts KD. A molecular membrane model of sperm capacitation and the acrosome reaction of mammalian spermatozoa. Gamete Res 1985; 12: 183–224. Leclerc P., de Lamirande E., Gagnon C. Cyclic adenosine 3′,5′-monophosphate-dependent regulation of protein tyrosine phosphorylation in relation to human sperm capacitation and motility. Biol Reprod 1996; 55: 684–692. Leclerc P., de Lamirande E., Gagnon C. Regulation of protein-tyrosine phosphorylation and human sperm capacitation by reactive oxygen derivatives. Free Rad Biol Med 1997; 22: 643–656. Lee MA, Storey BT. Bicarbonate is essential for fertilization of mouse eggs; mouse sperm require it to undergo the acrosome reaction. Biol Reprod 1986; 34: 349–356. Lee MA, Trucco GS, Bechtol KB, Wummer N., Kopf GS, Blasco L., Storey BT. Capacitation and acrosome reactions in human spermatozoa monitored by a chlortetracycline fluorescence assay. Fertil Steril 1987; 48: 649–658. Luconi M., Krausz C., Forti G., Baldi E. Extracellular calcium negatively modulates tyrosine phosphorylation and tyrosine kinase activity during capacitation of human spermatozoa. Biol Reprod 1996; 55: 207–216. Mahadevan MM, Miller MM, Moutos DM. Absence of glucose decreases human fertilization and sperm movement characteristics in vitro. Hum Reprod 1997; 12: 119–123. Miller DJ, Winer MA, Ax RL. Heparin-binding proteins from seminal plasma bind to bovine spermatozoa and modulate capacitation by heparin. Biol Reprod 1990; 42: 899–915. Neill J., Olds-Clarke P. A computer-assisted assay for mouse sperm hyperactivation demonstrates that bicarbonate but not bovine serum albumin is required. Gamete Res 1987; 18: 121–140. Okamura N., Tajima Y., Soejima A., Masuda H., Sugita Y. Sodium bicarbonate in seminal plasma stimulates the motility of mammalian spermatozoa through the direct activation of adenylate cyclase. J Biol Chem 1985; 260: 9699–9705. Okamura N., Tajima Y., Sugita Y. Decrease in bicarbonate transport activities during epididymal maturation of porcine sperm. Biochem Biophys Res Commun 1988; 157: 1280–1287. Parkkila S., Rajaniemi H., Kellokumpu S. Polarized expression of a band 3-related protein in mammalian sperm cells. Biol Reprod 1993; 49: 326–331. Parrish JJ, Susko-Parrish J., Uguz C., First NL. Differences in the role of cyclic adenosine 3′,5′-monophosphate during capacitation of bovine sperm by heparin or oviduct fluid. Biol Reprod 1994; 51: 1099–1108. Parrish JJ, Susko-Parrish J., Winer MA, First NL. Capacitation of bovine sperm by heparin. Biol Reprod 1988; 38: 1171–1180. Rogers BJ, Perreault SD. Importance of glycolysable substrates for in vitro capacitation of human spermatozoa. Biol Reprod 1990; 43: 1064–1069. Saling PM, Storey BT. Mouse gamete interactions during fertilization in vitro: chlortetracycline as fluorescent probe for the mouse sperm acrosome reaction. J Cell Biol 1979; 83: 544–555. Shi Q-X, Roldan ERS. Bicarbonate/CO2 is not required for zona pellucida- or progesterone-induced acrosomal exocytosis of mouse spermatozoa but is essential for capacitation. Biol Reprod 1995; 52: 540–546. Spira B., Breitbart H. The role of anion channels in the mechanism of acrosome reaction in bull spermatozoa. Biochim Biophys Acta 1992; 1109: 65–73. Storey BT. Biochemistry of the induction and prevention of lipoperoxi-dative damage in human spermatozoa. Mol Hum Reprod 1997; 3: 203–213. Storey BT. Kopf GS. Fertilization in the Mouse: II. Spermatozoa. In: B. Dunbar, M. O'Rand, eds. A Comparative Overview of Mammalian Fertilization. New York: Plenum Press, Inc; 1991: 167–216. Suarez SS. Hyperactivated motility in sperm. J Androl 1996; 17: 331–335. Thérien I., Bleau G., Manjunath P. Phosphatidylcholine-binding proteins of bovine seminal plasma modulate capacitation of spermatozoa by heparin. Biol Reprod 1995; 52: 1372–1379. Thérien I., Manjunath P. Phospholipid-binding proteins of bovine seminal vesicles modulate HDL- and heparin-induced capacitation of spermatozoa. Biol Reprod 1996; 54(Suppl 1): 23. Uguz C., Vredenburgh WL, Parrish JJ. Heparin-induced capacitation but not intracellular alkalinization of bovine sperm is inhibited by Rp-adenosine-3′,5′-cyclic monophosphothioate. Biol Reprod 1994; 51: 1031–1039. Visconti PE, Bailey JL, Moore GD, Pan D., Olds-Clarke P., Kopf GS. Capacitation of mouse spermatozoa. I. Correlation between the capacitation state and protein tyrosine phosphorylation. Development 1995a; 121: 1129–1137. Visconti PE, Johnson L., Oyaski M., Fornés M., Moss SB, Gerton GL, Kopf GS. Regulation, localization, and anchoring of protein kinase A subunits during mouse sperm capacitation. Dev Biol 1997; 192: 351–363. Visconti PE, Moore GD, Bailey JL, Leclerc P., Connors SA, Pan D., Olds-Clarke P., Kopf GS. Capacitation of mouse spermatozoa. II. Protein tyrosine phosphorylation and capacitation are regulated by a cAMP-dependent pathway. Development 1995b; 121: 1139–1150. Visconti PE, Muschietti JP, Flawia MM, Tezon JG. Bicarbonate dependence of cAMP accumulation induced by phorbol esters in hamster spermatozoa. Biochim Biophys Acta 1990; 1054: 231–236. Vredenburgh-Wilberg WL, Parrish JJ. Intracellular pH of bovine sperm increases during capacitation. Mol Reprod Dev 1995; 40: 490–502. Ward CR, Storey BT. Determination of the time course of capacitation in mouse spermatozoa using a chlortetracycline fluorescence assay. Dev Biol 1984; 104: 287–296. White DR, Aitken RJ. Relationship between calcium, cyclic AMP, ATP, and intracellular pH and the capacity of hamster spermatozoa to express hyperactivated motility. Gamete Res 1989; 22: 163–177. Wolf DE, Hagopian SS, Isogima S. Changes in sperm plasma membrane lipid diffusibility after hyperactivation during in vitro capacitation in the mouse. J Cell Biol 1986; 102: 1372–1377. Yanagimachi R. Mammalian fertilization. In: E. Knobil, JD Neill, eds. The Physiology of Reproduction. New York: Raven Press, Ltd; 1994: 189–317. Zeng Y., Clark EN, Florman HM. Sperm membrane potential: hyperpolarization during capacitation regulates zona pellucida-dependent acrosomal secretion. Dev Biol 1995; 171: 554–563. Zeng Y., Oberdorf JA, Florman HM. pH regulation in mouse sperm. Identification of Na+, Cl− and HCO3− -dependent and arylaminobenzoate-dependent regulatory mechanisms and characterization of their role in sperm capacitation. Dev Biol 1996; 173: 510–520. Citing Literature Volume19, Issue2March‐April 1998Pages 242-248 ReferencesRelatedInformation

Signal transduction pathways regulate various aspects of mammalian sperm function. When human sperm were incubated in a medium supporting capacitation, proteins became tyrosine-phosphorylated in a time-dependent manner. This phosphorylation was inhibited by genistein, a protein tyrosine kinase inhibitor. Phosphorylation was also reduced when sperm were incubated either in the presence of increasing concentrations of extracellular Ca2+ or in a medium containing the Ca2+ ionophore A23187. This Ca2+-induced dephosphorylation was calmodulin-dependent, suggesting that calcineurin was involved. In this regard, the calcineurin inhibitor deltamethrin inhibited the Ca2+ ionophore-induced dephosphorylation. A limited number of Mr 80,000-105,000 polypeptides were the most prominent phosphotyrosine-containing proteins present in human sperm. Unlike mouse sperm, which contains a tyrosine-phosphorylated isoform of hexokinase, a phosphotyrosine-containing hexokinase in human sperm was not detected. Most of the tyrosine-phosphorylated proteins were Triton X-100-insoluble and were localized to the principal piece of the flagellum, the region where the cytoskeletal fibrous sheath is found. Prominent phosphotyrosine-containing proteins of Mr 82,000 and 97,000 were identified as the human homologues of mouse sperm AKAP82, the major fibrous sheath protein, and pro-AKAP82, its precursor polypeptide, respectively. These proteins are A Kinase Anchor Proteins, polypeptides that sequester protein kinase A to subcellular locations. Taken together, these results suggest that protein tyrosine phosphorylation may be part of a signal transduction cascade(s) regulating events pertaining to capacitation and/or motility in mammalian sperm and that an interrelationship between tyrosine kinase and cAMP signaling pathways exists in these cells.

Intercellular communication between gametes is essential to the unique event in the life cycle of an organism called fertilization. Achievement of successful fertilization results from requisite and reciprocal cell-induced sperm and egg activation events mediated by unique cellular and environmental cues associated with either the gametes or the reproductive tract/environment. In the case of the sperm, the interaction of this highly motile cell with the female reproductive tract/environment, as well as with the egg both at a distance and in close proximity, represent a series of integrated processes designed to deliver sperm with optimal fertilizing potential to the site of fertilization. Recent studies have revealed that many aspects of gamete activation prior and subsequent to fertilization have similarities to intercellular and intracellular signaling systems utilized by somatic cells. Cell surface receptors or binding proteins on sperm for egg products have been identified in some species, while their identity in other species remains controversial. The occupancy of these receptors/binding proteins by egg products results in trans-membrane signaling and stimulation of intracellular effector systems, leading to subsequent sperm activation. Such activation events may include changes in motility, chemotaxis, and induction of acrosomal exocytosis, all of which may be essential prerequisites to successful fertilization in various species. This review will summarize what is known about these intercellular communicative events, with an emphasis on the mechanisms by which mammalian sperm process egg-associated signals via signal transduction pathways to effect changes in cellular function. The nature of these signaling systems is now being elucidated at the molecular level and has revealed some unique aspects of communication and transmembrane signaling between gametes. An understanding of signal transduction in mammalian sperm will ultimately yield information about the nature of the receptors to which these signal transduction pathways are coupled, as well as the intracellular effectors that ultimately regulate sperm function. Moreover, an understanding of these regulatory pathways will be essential for the future development of clinical approaches designed to enhance or preclude fertilization.