scholarly journals The role of calcium in the Chlamydomonas reinhardtii mating reaction.

1993 ◽  
Vol 121 (2) ◽  
pp. 365-374 ◽  
Author(s):  
U W Goodenough ◽  
B Shames ◽  
L Small ◽  
T Saito ◽  
R C Crain ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Sharp Increase ◽  
Intracellular Camp ◽  
Dibutyryl Camp ◽  
Mating Reaction ◽  
Flagellar Membrane ◽  
Camp Levels ◽  
Signal Transduction Systems ◽  
Related Increase

The mating reaction of Chlamydomonas reinhardtii entails a rapid series of cell-cell interactions leading to cell fusion. We have demonstrated (Pasquale, S. M., and U. Goodenough. 1987. J. Cell Biol. 105:2279-2293) that cAMP plays a key role in this process: gametic flagellar adhesion elicits a sharp increase in intracellular cAMP, and presentation of dibutyryl-cAMP to unmated gametes elicits all known mating responses. The present study evaluates the role of Ca2+ in this system. We document that the mating-induced increase in cAMP, and hence the mating responses themselves, are blocked by a variety of drugs known to interfere with Ca(2+)-sensitive processes. These data suggest that Ca(2+)-mediated events may couple adhesion to the generation of cAMP. Such events, however, appear to be localized to the flagellar membrane; we find no evidence for the mating-related increase in cytosolic free Ca2+ that has been postulated by others. Indeed, by monitoring the length of the Ca(2+)-sensitive centrin-containing nucleus-basal body connector, we show that cytosolic free Ca2+ levels, if anything, decrease in response to cAMP signaling. We confirm a previous report that Ca2+ levels increase in the mating medium, but document that this represents a response to augmented cAMP levels and not a prelude. Finally, we show that IP3 levels remain constant throughout the mating reaction. These results are discussed in terms of the various signal transduction systems that have now been identified in Chlamydomonas.

scholarly journals Cyclic AMP functions as a primary sexual signal in gametes of Chlamydomonas reinhardtii.

1987 ◽  
Vol 105 (5) ◽  
pp. 2279-2292 ◽  
Author(s):  
S M Pasquale ◽  
U W Goodenough
Keyword(s):  
Adenylate Cyclase ◽  
Chlamydomonas Reinhardtii ◽  
Mating Type ◽  
Cyclic Nucleotide ◽  
Actin Polymerization ◽  
Cyclic Nucleotide Phosphodiesterase ◽  
Intracellular Camp ◽  
Opposite Mating Type ◽  
Flagellar Membrane ◽  
Camp Levels

When Chlamydomonas reinhardtii gametes of opposite mating type are mixed together, they adhere by a flagella-mediated agglutination that triggers three rapid mating responses: flagellar tip activation, cell wall loss, and mating structure activation accompanied by actin polymerization. Here we show that a transient 10-fold elevation of intracellular cAMP levels is also triggered by sexual agglutination. We further show that gametes of a single mating type can be induced to undergo all three mating responses when presented with exogenous dibutyryl-cAMP (db-cAMP). These events are also induced by cyclic nucleotide phosphodiesterase inhibitors, which elevate endogenous cAMP levels and act synergistically with db-cAMP. Non-agglutinating mutants of opposite mating type will fuse efficiently in the presence of db-cAMP. No activation of mating events is induced by calcium plus ionophores, 8-bromo-cGMP, dibutyryl-cGMP, nigericin at alkaline pH, phorbol esters, or forskolin. H-8, an inhibitor of cyclic nucleotide-dependent protein kinase, inhibits mating events in agglutinating cells and antagonizes the effects of cAMP on non-agglutinating cells. Adenylate cyclase activity was detected in both the gamete cell body and flagella, with the highest specific activity displayed in flagellar membrane fractions. The flagellar membrane adenylate cyclase is preferentially stimulated by Mn++, unresponsive to NaF, GTP, GTP gamma S, AlF4-, and forskolin, and is inhibited by trifluoperazine. Cyclic nucleotide phosphodiesterase activity is also present in flagella. Our observations indicate that cAMP is a sufficient initial signal for all of the known mating reaction events in C. reinhardtii, and suggest that the flagellar cyclase and/or phosphodiesterase may be important loci of control for the agglutination-stimulated production of this signal.

scholarly journals Phosphodiesterases in endocrine physiology and disease

2011 ◽  
Vol 165 (2) ◽  
pp. 177-188 ◽  
Author(s):  
Delphine Vezzosi ◽  
Jérôme Bertherat
Keyword(s):  
Camp Signaling ◽  
Intracellular Camp ◽  
Potential Significance ◽  
Endocrine Diseases ◽  
Molecular Alterations ◽  
Regulatory Enzymes ◽  
Camp Signaling Pathway ◽  
Camp Levels ◽  
Endocrine Tissues

The cAMP–protein kinase A pathway plays a central role in the development and physiology of endocrine tissues. cAMP mediates the intracellular effects of numerous peptide hormones. Various cellular and molecular alterations of the cAMP-signaling pathway have been observed in endocrine diseases.Phosphodiesterases (PDEs) are key regulatory enzymes of intracellular cAMP levels. Indeed, PDEs are the only known mechanism for inactivation of cAMP by catalysis to 5′-AMP. It has been suggested that disruption of PDEs could also have a role in the pathogenesis of many endocrine diseases. This review summarizes the most recent advances concerning the role of the PDEs in the physiopathology of endocrine diseases. The potential significance of this knowledge can be easily envisaged by the development of drugs targeting specific PDEs.

THROMBIN-INDUCED RELEASE OF INTRA-PLATELET CA2+ STORES IS INHIBITED BY PROSTACYCLIN, BUT GTP- AND IP3-INDUCED RELEASE IS UNAFFECTED

1987 ◽  
Author(s):  
Michael F Crouch ◽  
Roger D Nolan ◽  
Eduardo G Lapetina
Keyword(s):  
Phosphatidic Acid ◽  
External Medium ◽  
Inositol Phosphates ◽  
Human Platelets ◽  
Direct Application ◽  
Total Cell ◽  
Intracellular Camp ◽  
Dibutyryl Camp ◽  
Tubular System ◽  
Camp Levels

Alpha-thrombin induced the release of internal Ca2+ stores and the influx of Ca2+ in human platelets, as measured by quin-2 fluorescence. This was accompanied by a stimulated formation of inositol phosphates and phosphatidic acid. The Ca2+ responses were inhibited almost totally by pretreatment of cells with prostacyclin (PGI2). Epinephrine was able to restore the influx of Ca2+ from the external medium, but not the alpha-thrombin-induced release of internal Ca2+ stores. This was despite epinephrine restoring phosphatidic acid formation and, at least partially, the generation of inositol trisphosphate (IP3). This suggested that PGI2 was inhibiting the actions of IP3 in inducing release of Ca2+ from the dense tubular system. Since the effects of PGI2 are thought to be mediated by formation of cAMP, we examined whether cAMP could modulate the release of 45Ca2+ induced by IP3 from permeabilized platelets. IP3 induced about a 30% release of cellular 45Ca2+ over a 4 min period. However, neither pretreatment of cells with PGI2 nor the direct application of dibutyryl cAMP had any effect on the IP3-stimulated 45Ca2+ release. GTP, which released about 10% of total cell 45Ca2+, also was not affected by these agents. These results suggest either that permeabilization of platelets dilutes cytoplasmic components which are necessary for cAMP action, or that PGI2 is inhibiting the release of Ca2+ stores induced by thrombin, presumably via IP3, by a mechanism which is separate to the elevation of intracellular cAMP levels.

cAMP and calcium-dependent mechanisms of phospholamban phosphorylation in intact hearts

1990 ◽  
Vol 258 (2) ◽  
pp. H318-H325 ◽  
Author(s):  
L. Vittone ◽  
C. Mundina ◽  
G. Chiappe de Cingolani ◽  
A. Mattiazzi
Keyword(s):  
Physiological Role ◽  
Intracellular Camp ◽  
Adrenergic Stimulation ◽  
Sr Protein ◽  
Myocardial Relaxation ◽  
Calcium Dependent ◽  
High Beta ◽  
Camp Levels ◽  
Phospholamban Phosphorylation

The present work was undertaken with two main goals: 1) to further elucidate the physiological role of the adenosine 3',5'-cyclic monophosphate (cAMP) and Ca2(+)-calmodulin (Ca2(+)-Cm)-dependent mechanisms of phospholamban phosphorylation (32PiPHL), and 2) to study the possible interaction between these two systems in the intact heart. Interventions that increased twitch or tetanic tension without modifying cAMP levels [high extracellular Ca2+ concentration [( Ca2+]o) or BAY K 8644 in catecholamine-depleted hearts] failed to alter 32PiPHL. Moderate and high beta-adrenergic stimulation (3 x 10(-9) and 3 x 10(-8) M isoproterenol, respectively) increased cAMP from 0.345 +/- 0.032 to 0.636 +/- 0.069 and 0.772 +/- 0.060 pmol/mg wet wt, and 32PiPHL from 26.8 +/- 4.1 to 58.6 +/- 13.1 and 174.7 +/- 13.8 pmol 32Pi/mg sarcoplasmic reticular [SR] protein, respectively. Both doses of isoproterenol produced an enhanced myocardial relaxation. Reversal of the positive inotropic effect of isoproterenol by interventions that decrease intracellular Ca2+ supply failed to reduce the enhancement in 32PiPHL and myocardial relaxation elicited by 3 x 10(-9) M isoproterenol but diminished the increase in 32PiPHL induced by 3 x 10(-8) M isoproterenol to 116.3 +/- 10.9 without significant changes in cAMP. Changes in myocardial relaxation closely paralleled the changes in 32PiPHL. These results suggest that 1) 32PiPHL may be enhanced by the cAMP-dependent mechanism independently of the Ca2(+)-Cm system, and 2) 32PiPHL and myocardial relaxation may be modified by intracellular Ca2+ changes only at high-intracellular cAMP levels.

Chloride secretion by canine tracheal epithelium: I. Role of intracellular cAMP levels

1982 ◽  
Vol 70 (3) ◽  
pp. 217-226 ◽  
Author(s):  
Philip L. Smith ◽  
Michael J. Welsh ◽  
Jeffrey S. Stoff ◽  
Raymond A. Frizzell
Keyword(s):  
Chloride Secretion ◽  
Tracheal Epithelium ◽  
Intracellular Camp ◽  
Camp Levels

scholarly journals Down-regulation by prostaglandins of type-II phospholipase A2 expression in guinea-pig alveolar macrophages: a possible involvement of cAMP

1998 ◽  
Vol 330 (1) ◽  
pp. 89-94 ◽  
Author(s):  
Daniel VIAL ◽  
Laurence ARBIBE ◽  
Nathalie HAVET ◽  
Claude DUMAREY ◽  
B. Boris VARGAFTIG ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Phospholipase A2 ◽  
Alveolar Macrophages ◽  
Intracellular Camp ◽  
Type Ii ◽  
Dibutyryl Camp ◽  
Down Regulation ◽  
Camp Phosphodiesterase ◽  
Tnf Α ◽  
Camp Levels

We have demonstrated previously that isolated guinea-pig alveolar macrophages (AM) synthesize type-II phospholipase A2 (PLA2-II) through a tumour necrosis factor-α (TNF-α)-dependent process. This synthesis is enhanced by lipopolysaccharide (LPS) and accompanied by a release of prostaglandin E2 (PGE2) into the medium. Because agents elevating intracellular cAMP, such as PGE2, have been shown to stimulate PLA2-II expression in various cell types, we investigated the modulation of PLA2-II synthesis by cAMP in AM. Surprisingly, incubation of AM with PGE2, dibutyryl-cAMP, cholera toxin or rolipram (an inhibitor of specific cAMP-phosphodiesterase) inhibited both basal and LPS-stimulated PLA2-II expression. The inhibitory effect of PGE2 was observed at concentrations similar to those released by AM. Moreover, treatment of AM with either aspirin or neutralizing PGE2 monoclonal antibody stimulated PLA2-II synthesis. These effects were closely correlated with the ability of these agents to modulate TNF-α release, which was decreased by dibutyryl-cAMP and exogenous PGE2, whereas neutralizing PGE2 antibody markedly increased this release. Hence, in contrast to other cell systems, we report that: (i) agents elevating intracellular cAMP levels down-regulate both basal and LPS-induced PLA2-II synthesis, (ii) prostaglandins exert a negative feedback effect on this synthesis, probably through an elevation of intracellular cAMP levels, and (iii) inhibition of TNF-α release may account, at least in part, for the down-regulation of PLA2-II expression by endogenously produced prostaglandins and cAMP-elevating agents.

Forskolin and thyrotrophin stimulation of rat FRTL-5 thyroid cell growth: the role of cyclic AMP

1987 ◽  
Vol 114 (2) ◽  
pp. 199-205 ◽  
Author(s):  
P. A. Ealey ◽  
C. A. Ahene ◽  
J. M. Emmerson ◽  
N. J. Marshall
Keyword(s):  
Cyclic Amp ◽  
Dose Range ◽  
Phosphodiesterase Inhibitor ◽  
Lag Phase ◽  
Thyroid Cell ◽  
Intracellular Camp ◽  
Camp Levels ◽  
Tsh Stimulation ◽  
Stimulation Of

ABSTRACT The adenylate cyclase stimulator forskolin increases intracellular cyclic AMP (cAMP) in rat FRTL-5 cells within minutes and, after a lag phase of 20–24 h, an increase of cells in metaphase is seen. The dose– response relationships were similar in both systems, with significant increases in the number of metaphases observed at ∼0·1 μmol/l and a doubling of cAMP levels at 1 μmol/l, whilst doses of 0·1 mmol/l and above proved cytotoxic. An involvement of intracellular cAMP as a positive intermediate in cell division was further suggested by the finding that a low dose of forskolin (0·1 μmol/l) potentiated TSH stimulation of mitosis. Isobutyl methyl xanthine (IBMX), a phosphodiesterase inhibitor, also acted as a mitogen and potentiated TSH action. Moreover, the simultaneous inclusion of low doses of IBMX and forskolin additionally potentiated TSH stimulation of mitosis. An analogue of cAMP, dibutyryl cAMP, also stimulated mitosis and acted over a restricted dose range, with maximal stimulation at 1 mmol/l. We conclude that cAMP may act as a positive signal for FRTL-5 thyroid cell proliferation. J. Endocr. (1987) 114, 199–205

Reversal of increased microvascular permeability associated with ischemia-reperfusion: role of cAMP

1992 ◽  
Vol 72 (1) ◽  
pp. 389-395 ◽  
Author(s):  
A. F. Seibert ◽  
W. J. Thompson ◽  
A. Taylor ◽  
W. H. Wilborn ◽  
J. Barnard ◽  
...  
Keyword(s):  
Ischemia Reperfusion ◽  
Microvascular Permeability ◽  
Oxidant Injury ◽  
Dibutyryl Camp ◽  
Hemodynamic Changes ◽  
Beneficial Effects ◽  
Camp Analogue ◽  
Adenylate Cyclase Activation ◽  
Camp Levels

Ischemia-reperfusion (IR) is a form of oxidant injury known to increase microvascular permeability in the lung. Agents that increase adenosine 3′,5′-cyclic monophosphate (cAMP) levels have been shown to have beneficial effects in several models of oxidant lung injury associated with increased microvascular permeability. We investigated the role of adenylate cyclase activation with isoproterenol (ISO) or forskolin (FSK) in reversing the increased microvascular permeability associated with IR. ISO or FSK administered after 45 min of ischemia and 46 min of reperfusion caused a reduction in the capillary filtration coefficient (Kfc) from 1.25 +/- 0.13 to 0.53 +/- 0.08 and 0.55 +/- 0.10 ml.min-1.cmH2O–1.100 g tissue-1, respectively, at 90 min of reperfusion. This reduction in Kfc was accompanied by a rise in perfusate cAMP levels from 16.5 +/- 4.9 and 31.2 +/- 11.9 pmol/ml at 45 min of reperfusion to 444.2 +/- 147.8 and 276.1 +/- 91.0 pmol/ml at 105 min of reperfusion in lungs treated with ISO or FSK, respectively, at 46 min of reperfusion. Dibutyryl cAMP (DBcAMP), a membrane-permeable cAMP analogue, mimicked the permeability effect by reducing Kfc to 0.67 +/- 0.15 at 90 min of reperfusion. Significant hemodynamic changes occurred but were small and cannot explain the observed effect on Kfc. Photomicrographs from lungs treated with ISO or FSK revealed a reversal of the morphological manifestations of increased microvascular permeability. We conclude that the increased microvascular permeability associated with IR can be reversed by ISO, FSK, and DBcAMP and that cAMP produced by the lung contributes to the observed reversal.

scholarly journals Autoantibodies to β1-adrenergic receptor: pathogenetic role, mechanisms of action and methods of determination

2020 ◽  
pp. 20-26
Author(s):  
М.М. Пекло ◽  
Л.Н. Липатова ◽  
Е.И. Герасимова
Keyword(s):  
Adrenergic Receptor ◽  
Enzyme Linked Immunosorbent Assay ◽  
Intracellular Camp ◽  
Pathogenetic Role ◽  
Functional Methods ◽  
Biologic Activity ◽  
Healthy Donors ◽  
Camp Levels ◽  
Cultured Cardiomyocytes

Аутоантитела к β1-адренорецептору (АДРБ1 АТ) часто обнаруживаются в сыворотке пациентов с хронической сердечной недостаточностью, обусловленной различными этиологическими факторами. АДРБ1 АТ выявляются также и у некоторых здоровых доноров, однако они отличаются по своим функциональным свойствам от антител крови больных. Патогенетическая роль АДРБ1 АТ была продемонстрирована в различных модельных экспериментах на животных. Рассмотрены предполагаемые патогенетические механизмы действия АДРБ1 АТ. Приводятся различные данные, свидетельствующие о предполагаемой особой роли аутоантител подкласса IgG3 в развитии сердечно-сосудистых патологий. В клинической практике наличие АДРБ1 АТ в крови больных играет прогностическую роль , а так же может являться маркером желудочковых нарушений ритма сердца. Анализируются различные методы выявления АДРБ1 АТ: иммуноферментный анализ с использованием пептидов в качестве антигена, а также методы с использованием в качестве антигена нативной молекулы адренорецептора. Наиболее информационно значимыми являются функциональные методы определения АДРБ1 АТ, в которых исследуется их биологическая активность. Такими методами авляются определение хронотропного эффекта антител на культурах кардиомиоцитов, а также детектирование подъема концентрации цАМФ на линиях клеток, экспрессирующих молекулу адренорецептора. Autoantibodies to β1-adrenergic receptor (β1ADR Ab) are often found in the serum of patients with congestive heart failure due to various etiologic factors. β1ADR Abs also occur in some healthy donors, however, such antibodies differ by their functional characteristics from those discovered in the blood of diseased subjects. Pathogenetic role of β1ADR Abs has been demonstrated in various animal models. Presumed pathogenetic mechanisms of β1ADR Ab action have been reviewed. Different evidences for putative specific role of IgG3 autoantibodies in the development of cardiovascular disorders are presented. In clinical practice, the presence of β1ADR Abs in patients’ blood has a prognostic value and can also be a marker of ventricular cardiac rhythm disturbances. Different methods of β1ADR Abs detection have been reviewed, including enzyme-linked immunosorbent assay using peptides as antigens and methods utilizing a native molecule of adrenergic receptor as an antigen. The highest informative value have the functional methods of β1ADR Abs detection, which are based on the evaluation of their biologic activity. These methods include the measuring of the chronotropic effect of antibodies in cultured cardiomyocytes and detection of increase in intracellular cAMP levels in cell lines expressing the molecules of adrenergic receptor.

Regulation of Na+-K+-Cl−cotransporter in primary astrocytes by dibutyryl cAMP and high [K+]o

2000 ◽  
Vol 279 (6) ◽  
pp. C1710-C1721 ◽  
Author(s):  
Gui Su ◽  
Robert A. Haworth ◽  
Robert J. Dempsey ◽  
Dandan Sun
Keyword(s):  
Channel Blocker ◽  
Intracellular Camp ◽  
Dependent Manner ◽  
Dibutyryl Camp ◽  
Cortical Astrocyte ◽  
High K ◽  
Voltage Dependent ◽  
Astrocyte Differentiation ◽  
Stimulation Of

In this study, we examined the Na+-K+-Cl− cotransporter activity and expression in rat cortical astrocyte differentiation. Astrocyte differentiation was induced by dibutyryl cAMP (DBcAMP, 0.25 mM) for 7 days, and cells changed from a polygonal to process-bearing morphology. Basal activity of the cotransporter was significantly increased in DBcAMP-treated astrocytes ( P < 0.05). Expression of an ∼161-kDa cotransporter protein was increased by 91% in the DBcAMP-treated astrocytes. Moreover, the specific [3H]bumetanide binding was increased by 67% in the DBcAMP-treated astrocytes. Inhibition of protein synthesis by cyclohexamide (2–3 μg/ml) significantly attenuated the DBcAMP-mediated upregulation of the cotransporter activity and expression. The Na+-K+-Cl−cotransporter in astrocytes has been suggested to play a role in K+ uptake. In 75 mM extracellular K+concentration, the cotransporter-mediated K+ influx was stimulated by 147% in nontreated cells and 79% in DBcAMP-treated cells ( P < 0.05). To study whether this high K+-induced stimulation of the cotransporter is attributed to membrane depolarization and Ca2+ influx, the role of the L-type voltage-dependent Ca2+ channel was investigated. The high-K+-mediated stimulation of the cotransporter activity was abolished in the presence of either 0.5 or 1.0 μM of the L-type channel blocker nifedipine or Ca2+-free HEPES buffer. A rise in intracellular free Ca2+ in astrocytes was observed in high K+. These results provide the first evidence that the Na+-K+-Cl− cotransporter protein expression can be regulated selectively when intracellular cAMP is elevated. The study also demonstrates that the cotransporter in astrocytes is stimulated by high K+ in a Ca2+-dependent manner.

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