Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The involvement of anion channels in the mechanism of the acrosome reaction (AR) was investigated. The AR was induced by Ca2+ or by addition of the Ca2+ ionophore A23187. The occurrence of AR was determined by following the release of acrosin from the cells. In order to investigate the role of anion channels in the AR, several anion-channel inhibitors were tested, mainly DIDS (4,4'-diisothiocyanostilbene-2,2'-disulfonic acid). Other blockers, like SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid), furosemide, probenecid and pyridoxal 5-phosphate, were also tested. We found that DIDS binds covalently to sperm plasma membrane in a time- and concentration-dependent manner. Maximal binding occurs after 2 h with 0.3 mM DIDS. DIDS and SITS inhibit AR in a concentration-dependent manner. The IC50 of DIDS and SITS in the presence of A23187 is 0.15 and 0.22 mM, respectively. Tributyltin chloride (TBTC), an Cl-/OH- exchanger, partially overcomes DIDS inhibition of the AR. HCO3- is required for a maximal acrosin release and Ca(2+)-uptake, in the presence or absence of A23187. It is known that HCO3- activates adenylate cyclase and therefore, increases the intracellular level of cAMP. The inhibition of the AR by DIDS decreases from 95 to 50% when (dibutyryl cyclic AMP (dbcAMP) was added, i.e., HCO3- is no longer required while elevating the level of cAMP in an alternative way. Moreover, we show that the stimulatory effect of HCO3- on Ca(2+)-uptake is completely inhibited by DIDS. We conclude that DIDS inhibits AR by blocking anion channels, including those that transport HCO3- into the cell.
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PMID:The role of anion channels in the mechanism of acrosome reaction in bull spermatozoa. 138 Mar

The analogue of the second messenger cAMP, dibutyryl cAMP (dbcAMP), was shown to induce the human sperm acrosome reaction to the same extent as calcium ionophore A23187, providing preliminary evidence for the involvement of the adenylate cyclase system in the acrosome reaction (AR) of human spermatozoa. Using the human synchronous acrosome reaction system, proteinase inhibitors were tested for their effect on the dbcAMP-induced human sperm acrosome reaction. The proteinase inhibitor 4'-acetamidophenyl 4-guanidinobenzoate (AGB), an inhibitor of proacrosin activation and of acrosin, when added at either the onset of incubation or to capacitated spermatozoa, 5 min prior to stimulation by dbcAMP, significantly (P less than 0.01) inhibited the acrosome reaction at final concentrations of 1 x 10(-4) M to 1 x 10(-6) M in comparison to dbcAMP treatment alone. At concentrations less than 1 x 10(-6) M, no significant inhibitory effect was seen. Similarly, para-aminobenzamidine (pAB), also an inhibitor of proacrosin activation and of acrosin, significantly (P less than 0.01) inhibited the dbcAMP-induced acrosome reaction at final concentrations of 1 x 10(-4) M to 1 x 10(-6) M when added at either the onset of incubation or to capacitated spermatozoa, 5 min prior to stimulation by dbcAMP, in comparison to stimulation by dbcAMP alone. However, at concentrations less than 1 x 10(-6) M, no significant (P greater than 0.05) inhibitory effect was seen. These results indicate that a serine proteinase, most likely acrosin, has a role in the human sperm acrosome reaction and suggest that the enzyme functions after the involvement of the adenylate cyclase system.
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PMID:Inhibition of the human sperm acrosome reaction by proteinase inhibitors. 255 Mar 39

The beta-adrenoceptor adenylate cyclase complex (beta ACR), located in the sarcolemmal membrane, is one of the most effective signal transduction systems regulating function and metabolism of heart muscle primarily via cyclic AMP. It is thought to play an important role in adaptive mechanisms of the heart as to pressure load and stressful stimuli. Present knowledge about composition and function of beta ARC enable us to clear up which of the single components of this system contributes to pathophysiological alterations of heart function. Cardiac beta ARC was investigated in three experimental groups: I) adult rats of WKY strain (WKY), II) adult rats of WKY strain cardiac hypertrophy in which was induced by aortic constriction (WKYAC), and III) adult spontaneously hypertensive rats (SHR). Quantitative assessment of beta-adrenoceptor number (beta AR) as revealed by [3H]dihydroalprenolol binding studies showed a significant reduction to 30% and 35% of control beta AR in membrane preparations of WKYAC and SHR, respectively. The diminished density of myocardial beta AR was accompanied by a reduction of the maximum stimulatory effect of 1(-)adrenaline on adenylate cyclase (AC). Evidence was obtained for a close correlation between the diminished response of beta ARC to beta AR-mediated stimuli and the heart index as measure of cardiac hypertrophy. No correlation between graduated states of hypertrophy and activation of AC has been observed by NaF and Gpp(NH)p. The results indicate that in rat hearts severe hypertrophy of which was induced by pressure-load, mainly the beta AR component of the beta ARC complex contributes to the reduction of beta ARC-mediated responsiveness of the hypertrophied myocardium.
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PMID:Signal transfer in cardiac muscle. Alteration of the beta-adrenoceptor adenylate cyclase system in the hypertrophied myocardium. 300 9

The effects of trypsin, acrosin and a recently described trypsin-like protease from bovine sperm were studied on adenylate cyclase activity in membranes of human platelets. These proteases caused an immediate decrease in adenylate cyclase activity, which was independent of the platelet membrane concentration used and which was constant for up to 20 min of incubation at 25 degrees C. When the incubation was prolonged, the proteases eliminated their own inhibitory action as well as that of the inhibitory hormone epinephrine. The adenylate cyclase inhibition caused by the proteases was strictly dependent on the presence of GTP (EC50 approximately 0.1 microM), whereas in the absence of GTP only minor changes in enzyme activity were observed at the conditions and protease concentrations used. Maximal inhibition caused by the proteases was between 40% and 60%. Half-maximal inhibition by the purified proteases trypsin and acrosin was observed at about 30 ng/ml and 2 micrograms/ml respectively. Inhibition of platelet adenylate cyclase by the proteases was partially additive with that caused by epinephrine, while with thrombin no additivity was observed. The serine protease inhibitor leupeptin blocked the actions of the proteases when added simultaneously with the enzymes, but was ineffective when added later on. Treatment of platelet membranes with the alkylating N-ethylmaleimide at low concentrations and Mn2+ ions (greater than or equal to 1 mM), both agents known to abolish inhibition of adenylate cyclase via the inhibitory guanine-nucleotide-binding protein Gi, eliminated the inhibitory action of the proteases. The data indicate that trypsin and trypsin-like proteases have two opposite effects on the platelet adenylate cyclase system, the well-documented elimination of Gi action and, as shown here, an immediate activation of Gi with subsequent adenylate cyclase inhibition. The data are consistent with the hypothesis that the activation of Gi caused by the proteases is due to an interaction of the proteases with specific cell-surface receptor sites in a manner similar to thrombin.
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PMID:Thrombin-like inhibitory action of trypsin and trypsin-like proteases on human platelet adenylate cyclase. 327 7

We previously reported the activation of adenylate cyclases from rat brain (Johnson, R. A., Awad, J. A., Jakobs, K. H., and Schultz, G., (1983) FEBS Lett. 152, 11-16) and from human platelets (Jakobs, K. H., Johnson, R. A., and Schultz, G. (1983) Biochim. Biophys. Acta 756, 369-375) by a factor derived from bovine sperm. In this report we describe the conditions for the extraction of the factor from bovine sperm and characteristics of its effects on adenylate cyclase which are consistent with its being a protease. The activating capacity of sperm particles was extracted from previously washed and frozen sperm into a 30,000 X g supernatant fraction by various salts, but not by the nonionic detergent Lubrol-PX. The amount of extracted factor: (a) was greatest with NH4HCO3 greater than NaCl greater than Na acetate; (b) was optimal with 0.5 M salt; (c) was not appreciably affected by the pH of the extraction buffer between pH 5.0 and 8.5; and (d) exhibited the greatest specific activity at the lower pH. The extracted sperm factor could be concentrated without loss by ultrafiltration on Amicon PM-10 membranes. The effect on adenylate cyclase of concentrated and desalted sperm extracted was inhibited 50% by various salts at 10 to 30 mM. The effects of the sperm factor to activate platelet adenylate cyclase, to block its inhibition via the alpha-adrenoceptor, and to block inhibition of stimulated forms of the enzyme by stable guanine nucleotides were prevented by protease inhibitors. A 50% reduction in the sperm factor's activation of platelet adenylate cyclase was caused by 30 nM soybean trypsin inhibitor, 30 nM alpha 2-macroglobulin, 300 nM leupeptin, 1 microM antipain, 15 microM aprotinin, and 100 microM benzamidine. Up to 3 mM phenylmethanesulfonyl fluoride was without effect on activation of the platelet cyclase by the sperm factor. The effects of the sperm factor persisted after its removal by the washing of pretreated platelet membranes and after its inactivation by the subsequent addition of leupeptin. The data strongly support the conclusion that the bovine sperm factor is a trypsin-like protease. alpha-Chymotrypsin, trypsin, and sperm acrosin were comparably effective in stimulating the platelet adenylate cyclase 5- to 8-fold, with concentrations eliciting maximal stimulation being: 200 ng trypsin/ml; 2 micrograms alpha-chymotrypsin/ml; and 2 micrograms acrosin/ml.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Extraction of the adenylate cyclase-activating factor of bovine sperm and its identification as a trypsin-like protease. 388 Jul 36

Coordination of cell movement with cell differentiation is a major feat of embryonic development. The Dictyostelium stalk always forms at the organizing tip, by a mechanism that is not understood. We previously reported that cyclic diguanylate (c-di-GMP), synthesized by diguanylate cyclase A (DgcA), induces stalk formation. Here we used transcriptional profiling of dgca- structures to identify target genes for c-di-GMP, and used these genes to investigate the c-di-GMP signal transduction pathway. We found that knockdown of cAMP-dependent protein kinase (PKA) activity in prestalk cells reduced stalk gene induction by c-di-GMP, whereas PKA activation bypassed the c-di-GMP requirement for stalk gene expression. c-di-GMP caused a persistent increase in cAMP, which still occurred in mutants lacking the adenylate cyclases ACG or ACR, or the cAMP phosphodiesterase RegA. However, both inhibition of adenylate cyclase A (ACA) with SQ22536 and incubation of a temperature-sensitive ACA mutant at the restrictive temperature prevented c-di-GMP-induced cAMP synthesis as well as c-di-GMP-induced stalk gene transcription. ACA produces the cAMP pulses that coordinate Dictyostelium morphogenetic cell movement and is highly expressed at the organizing tip. The stalk-less dgca- mutant regained its stalk by expression of a light-activated adenylate cyclase from the ACA promoter and exposure to light, indicating that cAMP is also the intermediate for c-di-GMP in vivo. Our data show that the more widely expressed DgcA activates tip-expressed ACA, which then acts on PKA to induce stalk genes. These results explain why stalk formation in Dictyostelia always initiates at the site of the morphogenetic organizer.
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PMID:Adenylate cyclase A acting on PKA mediates induction of stalk formation by cyclic diguanylate at the Dictyostelium organizer. 2805 64