Role Of Soluble Adenylyl Cyclase Research Articles

The Role of Soluble Adenylyl Cyclase in the Regulation of Flagellar Motility in Ascidian Sperm.

Flagellar motility in sperm is activated and regulated by factors related to the eggs at fertilization. In the ascidian Ciona intestinalis, a sulfated steroid called the SAAF (sperm activating and attracting factor) induces both sperm motility activation and chemotaxis. Cyclic AMP (cAMP) is one of the most important intracellular factors in the sperm signaling pathway. Adenylyl cyclase (AC) is the key enzyme that synthesizes cAMP at the onset of the signaling pathway in all cellular functions. We previously reported that both transmembrane AC (tmAC) and soluble AC (sAC) play important roles in sperm motility in Ciona. The tmAC plays a major role in the SAAF-induced activation of sperm motility. On the other hand, sAC is involved in the regulation of flagellar beat frequency and the Ca2+-dependent chemotactic movement of sperm. In this study, we focused on the role of sAC in the regulation of flagellar motility in Ciona sperm chemotaxis. The immunochemical analysis revealed that several isoforms of sAC protein were expressed in Ciona sperm, as reported in mammals and sea urchins. We demonstrated that sAC inhibition caused strong and transient asymmetrization during the chemotactic turn, and then sperm failed to turn toward the SAAF. In addition, real-time Ca2+ imaging in sperm flagella revealed that sAC inhibition induced an excessive and prolonged Ca2+ influx to flagella. These results indicate that sAC plays a key role in sperm chemotaxis by regulating the clearance of [Ca2+]i and by modulating Ca2+-dependent flagellar waveform conversion.

FRI576 - Role of soluble adenylyl cyclase in the formation and growth of liver tumours

FRI576 - Role of soluble adenylyl cyclase in the formation and growth of liver tumours

Protective role of soluble adenylyl cyclase against reperfusion-induced injury of cardiac cells

AimsDisturbance of mitochondrial function significantly contributes to the myocardial injury that occurs during reperfusion. Increasing evidence suggests a role of intra-mitochondrial cyclic AMP (cAMP) signaling in promoting respiration and ATP synthesis. Mitochondrial levels of cAMP are controlled by type 10 soluble adenylyl cyclase (sAC) and phosphodiesterase 2 (PDE2), however their role in the reperfusion-induced injury remains unknown. Here we aimed to examine whether sAC may support cardiomyocyte survival during reperfusion. Methods and resultsAdult rat cardiomyocytes or rat cardiac H9C2 cells were subjected to metabolic inhibition and recovery as a model of simulated ischemia and reperfusion. Cytosolic Ca2+, pH, mitochondrial cAMP (live-cell imaging), and cell viability were analyzed during a 15-min period of reperfusion. Suppression of sAC activity in cardiomyocytes and H9C2 cells, either by sAC knockdown, by pharmacological inhibition or by withdrawal of bicarbonate, a natural sAC activator, compromised cell viability and recovery of cytosolic Ca2+ homeostasis during reperfusion. Contrariwise, overexpression of mitochondria-targeted sAC in H9C2 cells suppressed reperfusion-induced cell death. Analyzing cAMP concentration in mitochondrial matrix we found that inhibition of PDE2, a predominant mitochondria-localized PDE isoform in mammals, during reperfusion significantly increased cAMP level in mitochondrial matrix, but not in cytosol. Accordingly, PDE2 inhibition attenuated reperfusion-induced cardiomyocyte death and improved recovery of the cytosolic Ca2+ homeostasis. ConclusionsAC plays an essential role in supporting cardiomyocytes viability during reperfusion. Elevation of mitochondrial cAMP pool either by sAC overexpression or by PDE2 inhibition beneficially affects cardiomyocyte survival during reperfusion.

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OBJECTIVES/SPECIFIC AIMS: Our objective is to study the role of soluble adenylyl cyclase in the melanocyte regulation of pigment in response to ultraviolet radiation. Melanocytes are specialized cells that produce melanin in organelles called melanosomes, and melanin determines the pigmentation of hair and skin. cAMP is a master regulator of pigmentation and transmembrane class of adenylyl cyclases are essential for expression of important enzymes involved in melanogenesis. However, pigmentation is also controlled by melanosomal pH, which regulates melanogenesis, tyrosinase activity, and melanosome maturation. The relationship between melanosomal pH and cAMP has been elusive. Soluble adenylyl cyclase is a noncanonical source of cAMP that is not responsive to G proteins but rather functions as a pH sensor. We recently demonstrated that loss of soluble adenylyl cyclase (sAC) activity leads to increased melanosomal pH as well as increased pigmentation in cells and hair. We expanded our research to investigate the role of sAC in the intrinsic response of melanocytes to ultraviolet radiation. METHODS/STUDY POPULATION: We utilized sACfl/fl (wild type) and sACKO mouse melanocytes and compared their change in pigmentation in response to ultraviolet radiation. Melanin was used as a measure of pigmentation. We irradiated these cells at differing doses of UVB (0, 1, 2, or 3 mJ/cm2) daily for 3 days. After UVB treatment, cells were observed and the surviving cell numbers were determined. Cells were then analyzed for melanin content using spectroscopy. RESULTS/ANTICIPATED RESULTS: We found that while both sACfl/fl and sACKO cells had increased melanin content in response to UVB, the melanin content of sACKO cells increased more compared with sACfl/fl cells (p=0.001 at daily dose of 3 mJ/cm2). In addition, sACKO cells required less UVB dose to induce a response. We also observed that sACKO cells show increased cell death compared with sACfl/fl cells. DISCUSSION/SIGNIFICANCE OF IMPACT: Although both sACfl/fl and sACKO cells can induce melanin production in response to UV, our results suggest that sACKO cells are more sensitive. We believe that this increased response in sACKO cells is due to increased melanosomal pH. In addition, sACKO cells show increased cell death, suggesting that sAC is important in the damage response secondary to UV exposure. UV plays a wide range of roles in skin biology such as contributing to cancer risk and pigmentation. Since pigmentation is essential for the protection of the skin from UV insult, further investigation of possible mechanisms in which sAC can influence pigmentation in response to UV is warranted.

Inhibition of soluble adenylyl cyclase increases the radiosensitivity of prostate cancer cells

Pharmacological modulation of tumor radiosensitivity is a promising strategy for enhancing the outcome of radiotherapy. cAMP signaling plays an essential role in modulating the proliferation and apoptosis of different cell types, including cancer cells. Until now, the regulation of this pathway was restricted to the transmembrane class of adenylyl cyclases. In the present study, the role of an alternative source of cAMP, the intracellular localized soluble adenylyl cyclase (sAC), in the radiosensitivity of prostate cancer cells was investigated. Pharmacological inhibition of sAC activity led to marked suppression of proliferation, lactate dehydrogenase release, and induction of apoptosis. The combination of ionizing radiation with partial suppression of sAC activity (~50%) immediately after irradiation synergistically inhibited proliferation and induced apoptosis. Overexpression of sAC in normal prostate epithelial PNT2 cells increased the cAMP content and accelerated cell proliferation under control conditions. The effects of radiation were significantly reduced in transformed PNT2 cells compared with control cells. Analysis of the underlying cellular mechanisms of sAC-induced radioresistance revealed the sAC-dependent activation of B-Raf/ERK1/2 signaling. In agreement with this finding, inhibition of ERK1/2 in prostate cancer cells enhanced the cytotoxic effect of irradiation. In conclusion, the present study suggests that sAC-dependent signaling plays an important role in the radioresistance of prostate cancer cells. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease.

A HCO3−-dependent mechanism involving soluble adenylyl cyclase for the activation of Ca2+ currents in locus coeruleus neurons

Hypercapnic acidosis activates Ca2+ channels and increases intracellular Ca2+ levels in neurons of the locus coeruleus, a known chemosensitive region involved in respiratory control. We have also shown that large conductance Ca2+-activated K+ channels, in conjunction with this pathway, limits the hypercapnic-induced increase in firing rate in locus coeruleus neurons. Here, we present evidence that the Ca2+ current is activated by a HCO3−-sensitive pathway. The increase in HCO3− associated with hypercapnia activates HCO3−-sensitive adenylyl cyclase (soluble adenylyl cyclase). This results in an increase in cyclic adenosine monophosphate levels and activation of Ca2+ channels via cyclic adenosine monophosphate-activated protein kinase A. We also show the presence of soluble adenylyl cyclase in the cytoplasm of locus coeruleus neurons, and that the cyclic adenosine monophosphate analogue db-cyclic adenosine monophosphate increases Ca2+i. Disrupting this pathway by decreasing HCO3− levels during acidification or inhibiting either soluble adenylyl cyclase or protein kinase A, but not transmembrane adenylyl cyclase, can increase the magnitude of the firing rate response to hypercapnia in locus coeruleus neurons from older neonates to the same extent as inhibition of K+ channels. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease.

Soluble adenylyl cyclase of sea urchin spermatozoa

Fertilization, a key step in sexual reproduction, requires orchestrated changes in cAMP concentrations. It is notable that spermatozoa (sperm) are among the cell types with extremely high adenylyl cyclase (AC) activity. As production and consumption of this second messenger need to be locally regulated, the discovery of soluble AC (sAC) has broadened our understanding of how such cells deal with these requirements. In addition, because sAC is directly regulated by HCO3− it is able to translate CO2/HCO3−/pH changes into cAMP levels. Fundamental sperm functions such as maturation, motility regulation and the acrosome reaction are influenced by cAMP; this is especially true for sperm of the sea urchin (SU), an organism that has been a model in the study of fertilization for more than 130years. Here we summarize the discovery and properties of SU sperm sAC, and discuss its involvement in sperm physiology. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease.

Soluble adenylyl cyclase in health and disease

The second messenger cAMP is integral for many physiological processes. Soluble adenylyl cyclase (sAC) was recently identified as a widely expressed intracellular source of cAMP in mammalian cells. sAC is evolutionary, structurally, and biochemically distinct from the G-protein-responsive transmembranous adenylyl cyclases (tmAC). The structure of the catalytic unit of sAC is similar to tmAC, but sAC does not contain transmembranous domains, allowing localizations independent of the membranous compartment. sAC activity is stimulated by HCO3−, Ca2+ and is sensitive to physiologically relevant ATP fluctuations. sAC functions as a physiological sensor for carbon dioxide and bicarbonate, and therefore indirectly for pH. Here we review the physiological role of sAC in different human tissues with a major focus on the lung. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease, guest edited by J. Buck and L.R. Levin.

The role of soluble adenylyl cyclase in RAF regulation

The role of soluble adenylyl cyclase in RAF regulation

Role of soluble adenylyl cyclase in the heart

This review discusses the potential place of soluble adenylyl cyclase (sAC) in the framework of signaling in the cardiovascular system. cAMP has been studied as a critical and pleiotropic second messenger in cardiomyocytes, endothelial cells, and smooth muscle vascular cells for many years. It is involved in the transduction of signaling by catecholamines, prostaglandins, adenosine, and glucagon, just to name a few. These hormones can act via cAMP by binding to a G protein-coupled receptor on the plasma membrane with subsequent activation of a heterotrimeric G protein and its downstream effector, transmembrane adenylyl cyclase. This has long been the canonical standard for cAMP production in a cell. However, the relatively recent discovery of a unique source of cAMP, sAC, creates the potential for a shift in this signaling paradigm. In fact, sAC has been shown to play a role in apoptosis in coronary endothelial cells and cardiomyocytes. Additionally, it links nutrient utilization with ATP production in the liver and brain, which suggests one of many potential roles for sAC in cardiac function. The possibility of producing cAMP from a source distal to the plasma membrane provides a critical new building block for reconstructing the cellular signaling infrastructure.

Inhibition of osteoclast formation and function by bicarbonate: Role of soluble adenylyl cyclase

High [HCO(3)(-)] inhibits and low [HCO(3)(-)] stimulates bone resorption, which mediates part of the effect of chronic acidosis or acid feeding on bone. Soluble adenylyl cyclase (sAC) is a bicarbonate sensor that can potentially mediate the effect of bicarbonate on osteoclasts. Osteoclasts were incubated in 0, 12, and 24 mM HCO(3)(-) at pH 7.4 for 7-8 days and assayed for tartrate-resistant acid phosphatase (TRAP) and vacuolar-ATPase expression, and H+ accumulation. Total number and area of TRAP (+) multinucleated osteoclasts was decreased by HCO(3)(-) in a dose-dependent manner. V-ATPase expression and H+ accumulation normalized to cell cross-sectional area or protein were not significantly changed. The HCO(3)(-) -induced inhibition of osteoclast growth and differentiation was blocked by either 2-hydroxyestradiol, an inhibitor of sAC or sAC knockdown by sAC specific siRNA. The model of HCO(3)(-) inhibiting osteoclast via sAC was further supported by the fact that the HCO(3)(-) dose-response on osteoclasts is flat when cells were saturated with 8-bromo-cAMP, a permeant cAMP analog downstream from sAC thus simulating sAC activation. To confirm our in vitro findings in intact bone, we developed a 1-week mouse calvaria culture system where osteoclasts were shown to be viable. Bone volume density (BV/TV) determined by micro-computed tomography (microCT), was higher in 24 mM HCO(3)(-) compared to 12 mM HCO(3)(-) treated calvaria. This HCO(3)(-) effect on BV/TV was blocked by 2-hydroxyestradiol. In summary, sAC mediates the inhibition of osteoclast function by HCO(3)(-), by acting as a HCO(3)(-) sensor.

Delivering an Acid Response

Pastor-Soler et al. used rat epididymus as a model system in which to investigate the role of soluble adenylyl cyclase (sAC), a form of adenylyl cyclase that is activated by bicarbonate, in the ability of epithelial cells to sense and respond to changes in pH. Clear cells, a subpopulation of epididymal epithelial cells, secrete protons into the epididymal lumen to maintain an acid pH. The rate of proton secretion depends on recycling of vacuolar H + ATPase (V-ATPase) between intracellular vesicles and the apical plasma membrane; however, the mechanisms governing this response remain unclear. Pastor-Soler et al. used reverse transcription polymerase chain reaction on rat epididymal epithelial cells harvested by laser capture microdissection combined with Western and immunofluorescence analysis of rat epididymus to confirm the presence of sAC in clear cells. The authors used confocal microscopy in combination with immunofluorescence and electron microscopy in combination with immunogold to monitor V-ATPase localization. In epididymus perfused with acidic saline, V-ATPase recycled between endosomes and the apical membrane, whereas alkaline pH promoted accumulation of V-ATPase in apical microvilli as did both a permeant analog of adenosine 3′,5′-monophosphate (cAMP) and bicarbonate. Pharmacologic inhibition of carbonic anhydrase indicated that bicarbonate production was essential for the response to alkaline pH but not to cAMP. Inhibition of sAC confirmed that this enzyme mediated the response to pH and to bicarbonate. This research establishes sAC as a critical mediator of a cellular response to changes in ambient pH, which may represent a widespread signaling pathway. N. Pastor-Soler, V. Beaulieu, T. N. Litvin, N. Da Silva, Y. Chen, D. Brown, J. Buck, L. R. Levin, S. Breton, Bicarbonate-regulated adenylyl cyclase (sAC) is a sensor that regulates pH-dependent V-ATPase recycling. J. Biol. Chem. 278 , 49523-49529 (2003). [Abstract] [Full Text]