CAMP signal transduction

Adenylyl cyclase in learning and memory. The cAMP-signal transduction cascade has been demonstrated to play a role critical to the formation of long-term memory in both cellular models and in animals. The specific adenylyl cyclases involved are being identified by current research. In AC1 mutant mice there is a partial disruption of long-term potentiation (LTP), a cellular model of... 

Studies of peripheral NE receptor function have also shown alterations in a2 receptor and cyclic adenosine 39,59-monophosphate (cAMP) function in patients with PTSD. Decreases in platelet adrenergic a2-receptor number (Perry et al. 1987), platelet basal adenosine, isoproterenol, forskohn-stimulated cAMP signal transduction (Lerer et al. 1987), and basal platelet monoamine oxidase (MAO) activity (Davidson et al. 1985) have been found in PTSD. These findings may reflect chronic high levels of NE release which lead to compensatory receptor down-regulation and decreased responsiveness. 

Marcil J, Schiffrin EL, Anand-Srivastava MB. 1996. Aberrant adenylyl cyclase/cAMP signal transduction and G protein levels in platelet from hypertensive patients improve with antihypertensive drug therapy. Hypertension 28 83-90. 

From the evidence accumulated so far, it seems likely that the cAMP signal transduction pathway will be a major effector of a stimulatory signal to the pars tuberalis, which can be regulated by melatonin [115]. The effect of aluminum as AlF41 has been studied on inositol phosphate accumulation, calcium mobilization, and cyclic AMP production in ovine pars tuberalis cells [116]. In the presence of 10 mmol L-1 LiCl, AlF41 stimulated the net accumulation of inositol phosphates over a 40-min incubation. Lithium is a known inhibitor of phosphatases in the inositol phosphate-recycling pathway. The results show the existence of a lithium-sensitive phosphoinositide signaling. 

Smith FD, Scott JD (2006) Anchored cAMP signaling onward and upward - a short history of compartmentalized cAMP signal transduction. Eur J Cell Biol 85 585-592... 

Ohmori, M., and Okamoto, S. (2004) Pho-toresponsive cAMP signal transduction in cyanobacteria. Photochem. Photobiol. Sci. 3, 503-511. 

The VACM-1 receptor is a membrane-associated protein with a single putative transmembrane domain that binds selectively AVP (XD — 2 nM), but cannot discriminate between VXR and V2R analogues. It is expressed in endothelial and medullary collecting duct cells and upon stimulation by AVP. It induces a mobilization of cytosolic-free Ca2+, decreases cAMP production and inhibits cellular growth via MAPK phosphorylation and p53 expression. The mechanism of action and physiological functions of this new receptor are not well understood, but it seems to participate in the regulation of AVP induced signal transduction pathways or of a yet unidentified peptide. 

PBAN binding to a receptor results in signal transduction events to stimulate the pheromone biosynthetic pathway (Fig. 5). Receptor activation results in the influx of extracellular calcium and has been demonstrated in a number of moths [163-168]. The increase in cytosolic calcium can directly stimulate pheromone biosynthesis in some moths [165-168] or it will stimulate the production of cAMP [169,170]. So far cAMP has only been implicated in signal... 

Fig. 5 Proposed signal transduction mechanisms that stimulate the pheromone biosynthetic pathway in Helicoverpa zea and Bombyx mori. It is proposed that PBAN binds to a G protein-coupled receptor present in the cell membrane that upon PBAN binding will induce a receptor-activated calcium channel to open causing an influx of extracellular calcium. This calcium binds to calmodulin and in the case of B. mori will directly stimulate a phosphatase that will dephosphorylate and activate a reductase in the biosynthetic pathway. In H. zea the calcium-calmodulin will activate adenylate cyclase to produce cAMP that will then act through kinases and/or phosphatases to stimulate acetyl-CoA carboxylase in the biosynthetic pathway...

The primary hormonal signals serve as extracellular signals that are interpreted by a signal transduction apparatus and turned into signals within the cell—these second messengers such as cAMP and fructose 2,6-bisphosphate warn individual enzymes within the cell about what s happening outside. 

Calcitonin lowers serum Ca2+ and Pi levels, primarily by inhibiting the process of bone resorption, but also by decreasing resorption of Pi and Ca2+ in the kidney. Calcitonin receptors are predictably found primarily on bone cells (osteoclasts) and renal cells, and generation of cAMP via adenylate cyclase activation plays a prominent role in hormone signal transduction. 

FIGURE 14-6 Main signaling pathways for histamine receptors. Histamine can couple to a variety of G-protein-linked signal transduction pathways via its four different receptors. The Hj receptor activates the phosphatidylinositol turnover via Gq/11 proteins. The other receptors either positively (H2 receptor) or negatively (H3 and H4 receptor) regulate adenylyl cyclase activity via Gs and GUo protein activation respectively. Several additional signaling pathways have been described, which are not shown. Abbreviations PfP2, phosphatidylinositol 4,5-bisphosphate PIC, phospholipase C AC, adenylyl cyclase ATP, adenosine triphosphate cAMP, cyclic AMP PKC, protein kinase C PICA, protein kinase A. 

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