Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a previous article, we suggested that gp273, the ligand molecule for sperm-egg interaction in the bivalve mollusk Unio elongatulus has functional carbohydrate epitopes in common with a human zona pellucida glycoprotein, probably ZP3. We demonstrated that: 1) anti-gp273-purified immunoglobulin G (IgG), which recognizes a carbohydrate gp273 epitope including a Lewisa-like structure, interacts with a zona pellucida protein; 2) human sperm specifically bind to gp273; and 3) binding is reversed by anti-gp273 IgG. In the present study, we confirm this suggestion by demonstrating that heat-solubilized zonae pellucidae reverse gp273-human sperm binding, that gp273-binding sites are restricted to the acrosomal region, and that gp273 induces the acrosome reaction in human sperm. We also demonstrated that gp273-binding sites on human sperm function as signaling receptors because exposure of spermatozoa to this glycoprotein results in significant stimulation of protein kinase C (PKC) activity. Because the PKC inhibitor, bisindolylmaleimide I, reverses both PKC activation and the acrosome reaction, this kinase is a key component of the signal transduction pathway activated by gp273 and leading to the exocytotic event.
 ...
PMID:Gp273, the ligand molecule for sperm-egg interaction in the bivalve mollusk, Unio elongatulus, binds to and induces acrosome reaction in human spermatozoa through a protein kinase C-dependent pathway. 1289 Jul 19

We determined if acrosomal reaction was influenced by exposure of sperm cells to two dietary phytochemicals, genistein isoflavone and beta-lapachone, using the rat model. Spermatozoa were capacitated in capacitating medium with or without genistein isoflavone and beta-lapachone, and the percentage of posttreatment acrosome reaction compared with controls was assessed with two fluorescent probes, chlortetracycline (CTC) and fluorescein isothiocyanate- Pisum sativum ag-glutinin conjugate (FITC-PSA). Spermatozoa were permeabilized in ethanol and labeled with the FITC-PSA or CTC to determine the acrosome status. The results revealed that calcium ionophore could induce acrosome reaction in spermatozoa and that acrosome-reacted sperm cells showed obvious darkness in the head region, whereas acrosome-intact sperm displayed bright fluorescence over the entire sperm head. The basic response and pattern of acrosome reaction status were significantly similar in both CTC and FITC assays and in both treatment (genistein and beta-lapachone) groups. It was observed that higher doses of both genistein and beta-lapachone significantly suppressed acrosome reaction and that this inhibitory effect was both dose- and time-dependent. It was stipulated that the observed genistein inhibition of acrosome reaction could be due to suppression of protein kinase C, and that beta-lapachone could inhibit acrosome reaction through direct cytotoxic effects on sperm cell membrane at higher doses. However, light microscopic examination indicated that both phytochemicals had no significant effect on sperm morphology. It is concluded that, in view of the fact that acrosome reaction is a physiological prerequisite for fertilization of most mammalian eggs, both genistein and beta-lapachone could potentially suppress male fertility via suppression of acrosome reaction at higher doses, but could enhance fertility by promoting acrosome reaction at lower doses. This bimodal mode of action of both phytochemicals could offer a potentially new dimension in the search for causes of male infertility and possibly for male contraceptive development.
 ...
PMID:Toxic potential of dietary genistein isoflavone and beta-lapachone on capacitation and acrosome reaction of epididymal spermatozoa. 1458 86

In boar spermatozoa, the capacitating agent bicarbonate has been shown to induce rapid changes both in plasma membrane lipid architecture and in motility; in each case, a PKA-dependent pathway is involved. Early bicarbonate-induced changes in protein phosphorylation were probed using a commercial antibody against the phosphorylated form of the consensus substrate site for cyclic AMP-dependent protein kinase. The antibody detected relatively few bands in sperm extracts, of which only a small number showed incubation-dependent changes. While the quantitative response varied between boar ejaculates, in general terms bicarbonate induced phosphorylation increases in bands of 96, 64, and 59 kDa within 80 sec. The changes reached a maximum after about 160 sec, declined somewhat thereafter, and then increased again slowly as incubation progressed further (up to 21 min). The bicarbonate-induced increases were strongly dependent on the presence of BSA in the incubation medium. They were inhibited by H89 (PKA inhibitor) but not by GF (PKC inhibitor), and were enhanced by papaverine (phosphodiesterase inhibitor) and by calyculin (protein phosphatase inhibitor). The cyclic AMP analogue cBIMPS was able to mimic bicarbonate action though its effect was less dramatic. Stearated Ht31, a permeable inhibitor of PKA's binding to A-kinase anchoring protein, did not affect either the intensity or the specificity of the bicarbonate-induced phosphorylation changes, though it blocked motility entirely. Immunocytochemical studies revealed marked bicarbonate-dependent phosphorylation changes in the post-acrosomal region of the head and in the neck, midpiece, and anterior regions of the tail. Fractionation of stimulated spermatozoa showed that all bands detectable with the antibody were bound to heads and to midpieces and associated large tail fragments; no bands were detected in either small tail or membrane fragments or in the cytoplasmic fraction. Differential extraction of the midpiece/large tail fraction revealed two protein bands with closely similar electrophoretic mobilities to the 96- and 59-kDa phosphorylated bands; MALDI-TOF analyses of these bands revealed both to be members of the Odf2 family.
 ...
PMID:Rapid PKA-catalysed phosphorylation of boar sperm proteins induced by the capacitating agent bicarbonate. 1473 95

Mammalian spermatozoa should reside in the female reproductive tract for a certain time before gaining the ability to fertilize. During this time, the spermatozoa undergo a series of biochemical processes collectively called capacitation. We recently demonstrated that actin polymerization is a necessary step in the cascade leading to capacitation. We demonstrate here for the first time a role for phospholipase D (PLD) in the induction of actin polymerization and capacitation in spermatozoa. The involvement of PLD is supported by specific inhibition of F-actin formation during sperm capacitation by PLD inhibitors and the stimulation of fast F-actin formation by exogenous PLD or phosphatidic acid (PA). Moreover, PLD activity is enhanced during capacitation before actin polymerization. Protein kinase A (PKA), known to be active in sperm capacitation, and protein kinase C (PKC), involved in the acrosome reaction, can both activate PLD and actin polymerization. We suggest that PKA- and PKC-dependent signal transduction pathways can potentially lead to PLD activation; however, under physiological conditions, actin polymerization depends primarily on PKA activity. Activation of PKA during capacitation causes inactivation of phospholipase C, and as a result, PKC activation is prevented. It appears that PKA activation promotes sperm capacitation whereas early activation of PKC during capacitation would jeopardize this process.
 ...
PMID:Crosstalk between protein kinase A and C regulates phospholipase D and F-actin formation during sperm capacitation. 1497 29

Tubulobulbar complexes may be part of the mechanism by which intercellular adhesion junctions are internalized by Sertoli cells during sperm release. These complexes develop in regions where Sertoli cells are attached to adjacent cells by intercellular adhesion junctions termed ectoplasmic specializations. At sites where Sertoli cells are attached to spermatid heads, tubulobulbar complexes consist of fingerlike processes of the spermatid plasma membrane, corresponding invaginations of the Sertoli cell plasma membrane, and a surrounding cuff of modified Sertoli cell cytoplasm. At the terminal ends of the complexes occur clusters of vesicles. Here we show that tubulobulbar complexes develop in regions previously occupied by ectoplasmic specializations and that the structures share similar molecular components. In addition, the adhesion molecules nectin 2 and nectin 3, found in the Sertoli cell and spermatid plasma membranes, respectively, are concentrated at the distal ends of tubulobulbar complexes. We also demonstrate that double membrane bounded vesicles are associated with the ends of tubulobulbar complexes and nectin 3 is present on spermatids, but is absent from spermatozoa released from the epithelium. These results are consistent with the conclusion that Sertoli cell and spermatid membrane adhesion domains are internalized together by tubulobulbar complexes. PKCalpha, a kinase associated with endocytosis of adhesion domains in other systems, is concentrated at tubulobulbar complexes, and antibodies to endosomal and lysosomal (LAMP1, SGP1) markers label the cluster of vesicles associated with the ends of tubulobulbar complexes. Our results are consistent with the conclusion that tubulobulbar complexes are involved with the disassembly of ectoplasmic specializations and with the internalization of intercellular membrane adhesion domains during sperm release.
 ...
PMID:Evidence that tubulobulbar complexes in the seminiferous epithelium are involved with internalization of adhesion junctions. 1508 82

The effect of nitric oxide (NO*) on the capacitation rates of cryopreserved bull spermatozoa and the participation of protein kinases in the capacitation process were evaluated. A pool of spermatozoa from four bulls were incubated in TALP medium in the presence of heparin (10 IU/ml) or sodium nitroprusside (SNP, 0.05-100 microM), a NO* donor. The participation of NO* was confirmed by the use of scavengers, i.e. methylene blue (50,100 microM) and hemoglobin (20-40 microg/ml). The role of nitric oxide synthase in heparin-induced capacitation was evaluated using enzyme inhibitors Nomega-nitro-L-arginine methyl ester (L-NAME) and Nomega-nitro-L-arginine (L-NA) in concentrations ranging from 1 to 500 microM. The effects of protein kinase A (PKA), protein kinase C (PKC) and protein tyrosine kinase (PTK), on NO*-induced capacitation were evaluated by incubation with specific inhibitors of these enzymes (H-89, 50 microM; bisindolylmaleimide I, 0.1 microM and genistein, 3 microM). The role of hydrogen peroxide or superoxide anion in NO*-induced capacitation was evaluated by incubation with catalase (20-100 microg/ml) or superoxide dismutase (SOD, 0.05-0.5 mg/ml), respectively. Capacitation percentages were determined by the fluorescence technique with chlortetracycline (CTC). SNP concentrations employed had no effect on progressive motility or sperm viability. Capacitation values of the 0.05 microM SNP treatment (31 +/- 5.15%) were similar to those of heparin treated samples (33 +/- 4.27%). Inhibitors of nitric oxide synthase (NOS) diminished capacitation percentages in a dose-dependent manner as did the addition of NO*- scavengers (P <0.05). The presence of PKA, PKC and PTK inhibitors likewise decreased capacitation percentages (6.25 +/- 0.71, 12.75 +/- 1.41, 9.00 +/- 1.41%, respectively). The presence of catalase or SOD in the incubation medium had no effect on capacitation percentages. These results indicate that NO* may be generated by a sperm NOS during heparin-induced capacitation and that exogenous NO* acts as a capacitation inducer and involves the participation of PKA, PKC and PTK as part of the intracellular mechanisms that lead to capacitation in cryopreserved bull spermatozoa.
 ...
PMID:Nitric oxide-induced capacitation of cryopreserved bull spermatozoa and assessment of participating regulatory pathways. 1558 7

Acrosome reaction (AR) is an exocytotic process of fundamental importance for the spermatozoon to fertilize the oocyte. The mechanisms mediating this process are only partially defined. The aim of the present study was to investigate the role of various kinases and the extracellular signal-regulated kinase (ERK) pathway in the induction of the AR and associated phosphorylation of tyrosine (Tyr) residues and of the threonine-glutamic acid-tyrosine (Thr-Glu-Tyr) motif that occurs in 80 and 105 kDa proteins (p80/p105). Human spermatozoa were capacitated and AR was induced with lysophosphatidylcholine in the presence of inhibitors of various kinases and of the ERK pathway. Phosphorylation of Tyr and of Thr-Glu-Tyr peaked 15 min after the induction of the AR. Both phosphorylations were prevented by inhibitors of protein kinase C, MEK, phosphoinositide 3-kinase and Akt but not by protein kinase A inhibitors. Phosphorylation of Thr-Glu-Tyr, but not Tyr, was decreased by inhibitors of protein tyrosine kinase and Grb2-SH2. All the inhibitors prevented lysophosphatidylcholine-induced AR, indicating the involvement of PKC, PKA, PTK, PI3K, Akt and the ERK pathway. These results show that phosphorylation of Tyr and Thr-Glu-Tyr are associated with the AR and are differently regulated by the various kinases emphasing the complexity of this process.
 ...
PMID:Various protein kinases regulate human sperm acrosome reaction and the associated phosphorylation of Tyr residues and of the Thr-Glu-Tyr motif. 1570 55

Capacitation is an essential process by which spermatozoa acquire fertilizing ability. Reactive oxygen species (ROS), protein kinase A (PKA), protein kinase C (PKC), protein tyrosine kinases (PTKs), and the extracellular signal-regulated protein kinase (ERK or mitogen-activated protein kinase [MAPK]) pathway regulate sperm capacitation. Our aim was to evaluate the phosphorylation of MEK (MAPK kinase or MAP2K) or MEK-like proteins in human sperm capacitation and its modulation by ROS and kinases. Immunoblotting using an anti-phospho-MEK antibody indicated that the phosphorylation of three protein bands (55, 94, and 115 kDa) increased in spermatozoa treated with fetal cord serum ultrafiltrate (FCSu), BSA, or isobutylmethylxanthine plus dibutyryl cAMP as capacitating agents. These phospho-MEK-like proteins are localized along the sperm flagellum. The MEK-inhibitors PD98059 and U126 prevented this phosphorylation, suggesting that these proteins are MEK-like proteins. The ROS scavengers prevented, and the addition of H(2)O(2) or spermine-NONOate (nitric oxide donor) triggered, the increase of phospho-MEK-like proteins. The capacitation-related increases in phospho-MEK-like proteins induced by FCSu, H(2)O(2), and spermine-NONOate were similarly modulated by PKA, PKC, and PTK, suggesting ROS as mediators in this phenomenon. These results indicate that phospho-MEK-like proteins are modulated by ROS and kinases and probably represent an intermediary step between the early events and the late tyrosine phosphorylation associated with capacitation.
 ...
PMID:Reactive oxygen species and protein kinases modulate the level of phospho-MEK-like proteins during human sperm capacitation. 1577 58

We investigated, using guinea-pig spermatozoa as a model, whether phospholipase A2 (PLA2) is involved in progesterone or zona pellucida (ZP)-stimulated acrosomal exocytosis, if progesterone enhances ZP-induced activation of PLA2, and mechanisms underlying PLA2 regulation. Spermatozoa were capacitated and labeled in low Ca2+ medium with [14C]choline chloride or [14C]arachidonic acid, washed, and then exposed to millimolar Ca2+ and progesterone and/or ZP. Each agonist stimulated decrease of phosphatidylcholine (PC) and release of arachidonic acid and lysoPC, indicative of PLA2 activation. Aristolochic acid (a PLA2 inhibitor) abrogated lipid changes and exocytosis, indicating that these lipid changes are essential for exocytosis. Exposure of spermatozoa to submaximal concentrations of both progesterone and ZP resulted in a synergistic increase of arachidonic acid and lysoPC releases, and exocytosis, suggesting that, under natural conditions, both agonists interact to bring about acrosomal exocytosis. Progesterone-induced PLA2 activation appears to be mediated by a GABA(A)-like receptor, because bicuculline (a GABA(A) receptor antagonist) blocked arachidonic acid release and exocytosis. In agreement with this, GABA mimicked progesterone actions. ZP-induced activation of PLA2 seemed to be transduced via G(i) proteins because pertussis toxin blocked arachidonic acid release and acrosomal exocytosis. PLA2 may be regulated by PKC because progesterone- or ZP-induced release of arachidonic acid was blocked by the PKC inhibitors staurosporine or chelerythrine chloride. PLA2 could also be regulated by the cAMP-PKA pathway; inclusion of the PKA inhibitor 14-22 amide or H-89 led to a reduction in arachidonic acid release or exocytosis after progesterone or ZP. Taken together, these results suggest that PLA2 plays an essential role in progesterone or ZP-stimulated exocytosis with progesterone priming ZP action.
 ...
PMID:Progesterone primes zona pellucida-induced activation of phospholipase A2 during acrosomal exocytosis in guinea pig spermatozoa. 1596 49

We investigated whether GABA activates phospholipase A2 (PLA2) during acrosomal exocytosis, and if the MEK-ERK1/2 pathway modulates PLA2 activation initiated by GABA, progesterone or zona pellucida (ZP). In guinea pig spermatozoa prelabelled with [14C]arachidonic acid or [14C]choline chloride, GABA stimulated a decrease in phosphatidylcholine (PC), and release of arachidonic acid and lysoPC, during exocytosis. These lipid changes are indicative of PLA2 activation and appear essential for exocytosis since inclusion of aristolochic acid (a PLA2 inhibitor) abrogated them, along with exocytosis. GABA activation of PLA2 seems to be mediated, at least in part, by diacylglycerol (DAG) and protein kinase C since inclusion of the DAG kinase inhibitor R59022 enhanced PLA2 activity and exocytosis stimulated by GABA, whereas exposure to staurosporine decreased both. GABA-, progesterone- and ZP-induced release of arachidonic acid and exocytosis were prevented by U0126 and PD98059 (MEK inhibitors). Taken together, our results suggest that PLA2 plays a fundamental role in agonist-stimulated exocytosis and that MEK-ERK1/2 are involved in PLA2 regulation during this process.
 ...
PMID:GABA, progesterone and zona pellucida activation of PLA2 and regulation by MEK-ERK1/2 during acrosomal exocytosis in guinea pig spermatozoa. 1609 15


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>