Biofilms and Cyclic di-GMP (c-di-GMP) Signaling: Lessons from Pseudomonas aeruginosa and Other Bacteria

The cyclic di-GMP (c-di-GMP) second messenger represents a signaling system that regulates many bacterial behaviors and is of key importance for driving the lifestyle switch between motile loner cells and biofilm formers. This review provides an up-to-date compendium of c-di-GMP pathways connected to biofilm formation, biofilm-associated motilities, and other functionalities in the ubiquitous and opportunistic human pathogen Pseudomonas aeruginosa This bacterium is frequently adopted as a model organism to study bacterial biofilm formation. Importantly, its versatility and adaptation capabilities are linked with a broad range of complex regulatory networks, including a large set of genes involved in c-di-GMP biosynthesis, degradation, and transmission.

Changes in Membrane Cholesterol Differentially Influence Preferential and Non-preferential Signaling of the M1 and M3 Muscarinic Acetylcholine Receptors

We have found earlier that changes in membrane cholesterol content have distinct impact on signaling via the M1, M2, or M3 receptors expressed in CHO cells (CHO-M1 through CHO-M3). Now we investigated whether gradual changes in membrane cholesterol exerts differential effects on coupling of the M1 and M3 muscarinic receptors to preferential signaling pathways through Gq/11 and non-preferential Gs G-proteins signaling. Changes in membrane cholesterol resulted in only marginal alterations of antagonist and agonist affinity of the M1 and M3 receptors, and did not influence precoupling of either subtype. Changes in membrane cholesterol did not influence parameters of carbachol-stimulated GTP-γ(35)S binding in CHO-M1 membranes while reduction as well as augmentation of membrane cholesterol lowered the efficacy but increased the potency of carbachol in CHO-M3 membranes. Gradual increase or decrease in membrane cholesterol concentration dependently attenuated agonist-induced inositolphosphates release while only cholesterol depletion increased basal values in both cell lines. Similarly, membrane cholesterol manipulation modified basal and agonist-stimulated cAMP synthesis via Gs in the same way in both cell lines. These results demonstrate that changes in membrane cholesterol concentration differentially impact preferential and non-preferential M1 and M3 receptor signaling. They point to the activated G-protein/effector protein interaction as the main site of action in alterations of M1 receptor-mediated stimulation of second messenger pathways. On the other hand, modifications in agonist-stimulated GTP-γ(35)S binding in CHO-M3 membranes indicate that in this case changes in ligand-activated receptor/G-protein interaction may also play a role.

Targeting of type I protein kinase A to lipid rafts is required for platelet inhibition by the 3',5'-cyclic adenosine monophosphate-signaling pathway

BACKGROUND

Platelet adhesion to von Willebrand factor (VWF) is modulated by 3',5'-cyclic adenosine monophosphate (cAMP) signaling through protein kinase A (PKA)-mediated phosphorylation of glycoprotein (GP)Ibβ. A-kinase anchoring proteins (AKAPs) are proposed to control the localization and substrate specificity of individual PKA isoforms. However, the role of PKA isoforms in regulating the phosphorylation of GPIbβ and platelet response to VWF is unknown.

OBJECTIVES

We wished to determine the role of PKA isoforms in the phosphorylation of GPIbβ and platelet activation by VWF as a model for exploring the selective partitioning of cAMP signaling in platelets.

RESULTS

The two isoforms of PKA in platelets, type I (PKA-I) and type II (PKA-II), were differentially localized, with a small pool of PKA-I found in lipid rafts. Using a combination of Far Western blotting, immunoprecipitation, proximity ligation assay and cAMP pull-down we identified moesin as an AKAP that potentially localizes PKA-I to rafts. Introduction of cell-permeable anchoring disruptor peptide, RI anchoring disruptor (RIAD-Arg11 ), to block PKA-I/AKAP interactions, uncoupled PKA-RI from moesin, displaced PKA-RI from rafts and reduced kinase activity in rafts. Examination of GPIbβ demonstrated that it was phosphorylated in response to low concentrations of PGI2 in a PKA-dependent manner and occurred primarily in lipid raft fractions. RIAD-Arg11 caused a significant reduction in raft-localized phosphoGPIbβ and diminished the ability of PGI2 to regulate VWF-mediated aggregation and thrombus formation in vitro.

CONCLUSION

We propose that PKA-I-specific AKAPs in platelets, including moesin, organize a selective localization of PKA-I required for phosphorylation of GPIbβ and contribute to inhibition of platelet VWF interactions.

[Cyclic Guanosine Monophosphate as a Mediator in Processes of Stress Signaling Transduction in Higher Plants]

Currently, biophysical mechanisms of stress signaling transduction became an object of consideration of researchers in connection with the urgent necessity to develop new techniques to enhance the sustainability and productivity of agricultural crops. The development of sensitive methods for the determination of cyclic guanosine monophosphate (cGMP) and comparative analysis of cGMP-dependent events in biological systems has contributed to progress in the understanding of the functioning of cGMP in plant cells. Currently, it is shown that cGMP as a secondary mediator is involved in such vital processes of growth and development of plants as seed germination, cell division, development of chloroplasts, flowering and regulation of stomatal movements. This review summarizes the available data in the literature about the role of cGMP in the responses of plant organisms to the action of stress factors of abiotic and biotic nature and its interaction with other intracellular mediators. With the use of existing ideas about the biophysical mechanisms of stress in plants, the basic elements of cGMP-dependent signal transduction system in a plant cell are considered.

Acetyl coenzyme A: a central metabolite and second messenger

Acetyl-coenzyme A (acetyl-CoA) is a central metabolic intermediate. The abundance of acetyl-CoA in distinct subcellular compartments reflects the general energetic state of the cell. Moreover, acetyl-CoA concentrations influence the activity or specificity of multiple enzymes, either in an allosteric manner or by altering substrate availability. Finally, by influencing the acetylation profile of several proteins, including histones, acetyl-CoA controls key cellular processes, including energy metabolism, mitosis, and autophagy, both directly and via the epigenetic regulation of gene expression. Thus, acetyl-CoA determines the balance between cellular catabolism and anabolism by simultaneously operating as a metabolic intermediate and as a second messenger.

Calcium mobilizing second messengers derived from NAD

Nicotinamide adenine dinucleotide (NAD) has been known since a long period of time as co-factor of oxidoreductases. However, in the past couple of decades further roles have been assigned to NAD. Here, metabolism of NAD to the Ca²⁺ mobilizing second messengers cyclic adenosine diphosphoribose, nicotinic acid adenine dinucleotide phosphate and adenosine diphosphoribose is reviewed. Moreover, the mechanisms of Ca²⁺ mobilization by these adenine nucleotides and their putative target Ca²⁺ channels, ryanodine receptors and transient receptor potential channels are discussed. This article is part of a Special Issue entitled: Cofactor-dependent proteins: evolution, chemical diversity and bio-applications.

Signaling in cells and organisms - calcium holds the line

Previous research has established calcium (Ca(2+)) and reactive oxygen species (ROS) as important cellular second messengers in eukaryotes. Recently, the occurrence of cell-to-cell moving Ca(2+) and ROS waves was reported in plants. This was paralleled by the discovery of long-distance wound-activated surface potential changes (WASPs) that require the function of putatively Ca(2+)-releasing glutamate receptor-like channels (GLRs) in Arabidopsis. Although the functional interconnection of Ca(2+)-dependent phosphorylation and ROS waves via NADPH oxidase activation has been clearly established, potential further interconnections between these long-distance signaling processes are less clear. In this review we cover emerging concepts and existing open questions that interconnect cellular and global signaling via Ca(2+), ROS and WASPs.

Phosphodiesterase 4 interacts with the 5-HT4(b) receptor to regulate cAMP signaling

Phosphodiesterase (PDE) 3 and PDE4, which degrade cyclic adenosine monophosphate (cAMP), are important regulators of 5-hydroxytryptamine (5-HT) 4 receptor signaling in cardiac tissue. Therefore, we investigated whether they interact with the 5-HT4(b) receptor, and whether A-kinase anchoring proteins (AKAPs), scaffolding proteins that bind to the regulatory subunit of protein kinase A (PKA) and contribute to the spacial-temporal control of cAMP signaling, are involved in the regulation of 5-HT4(b) receptor signaling. By measuring PKA activity in the absence and presence of PDE3 and PDE4 inhibitiors, we found that constitutive signaling of the overexpressed HA-tagged 5-HT4(b) receptor in HEK293 cells is regulated predominantly by PDE4, with a secondary role for PDE3 that is unmasked in the presence of PDE4 inhibition. Overexpressed PDE4D3 and PDE3A1, and to a smaller extent PDE4D5 co-immunoprecipitate constitutively with the 5-HT4(b) receptor. PDE activity measurements in immunoprecipitates of the 5-HT4(b) receptor confirm the association of PDE4D3 with the receptor and provide evidence that the activity of this PDE may be increased upon receptor stimulation with 5-HT. A possible involvement of AKAPs in 5-HT4(b) receptor signaling was uncovered in experiments using the St-Ht31 inhibitor peptide, which disrupts the interaction of AKAPs with PKA. However, St-Ht31 did not influence 5-HT4(b) receptor-stimulated PKA activity, and endogenous AKAP79 and gravin were not found in immunoprecipitates of the 5-HT4(b) receptor. In conclusion, we found that both PDE3A1 and PDE4D3 are integrated into complexes that contain the 5-HT4(b) receptor and may thereby regulate 5-HT4(b) receptor-mediated signaling.

The role of epigenetic-related codes in neurocomputation: dynamic hardware in the brain

This paper presents a review of recent work on the role that two epigenetic-related systems may play in information processing mechanisms in the brain. The first consists of exosomes that transport epigenetic-related molecules between neurons. The second consists of homeoproteins like Otx2 that carry information from sense organs to primary sensory cortex. There is developing evidence that presynaptic neurons may be able to modulate the fine microanatomical structure in the postsynaptic neuron. This may be conducted by three mechanisms, of which the first is well established and the latter two are novel. (i) By the well-established activation of receptors that trigger a chain of signalling molecules (second messengers) that result in the upregulation and/or activation of a transcription factor. The two novel systems are the exosome system and homeoproteins. (ii) Exosomes are small vesicles that are released upon activation of the axon terminal, traverse the synaptic cleft, probably via astrocytes and are taken up by the postsynaptic neuron. They carry a load of signalling proteins and a variety of forms of RNA. These loads may then be transported widely throughout the postsynaptic neuron and engineer modulations in the fine structure of computational machinery by epigenetic-related processes. (iii) Otx2 is a transcription factor that, inter alia, controls the development and survival of PV+ GABAergic interneurons (PV cells) in the primary visual cortex. It is synthesized in the retina and is transported to the cortex by a presently unknown mechanism that probably includes direct cell-to-cell transfer, and may, or may not, include transfer by the dynein and exosome systems in addition. These three mechanisms explain a quantity of data from the field of de- and reafferentation plasticity. These data show that the modality of the presynaptic neuron controls to a large extent the modality of the postsynaptic neuron. However, the mechanism that effects this is currently unknown. The exosome and the homeoprotein hypotheses provide novel explanations to add to the well-established earlier mechanism described above.

Multiple impacts of zinc on immune function

Even though zinc is essential for virtually all processes in the human body, observations during zinc deficiency indicate that the absence of this trace element most severely affects the immune response. Numerous investigations of the cellular and molecular requirements for zinc in the immune system have indicated that there is not just one single function of zinc underlying this essentiality. In fact, there is a wide range of different roles of zinc in immunity. This review summarizes the recent developments in three of the major fields: the role of zinc as a second messenger in signal transduction, the importance of zinc for immune cell function, and the competition for zinc between the host and the pathogen, a concept known as nutritional immunity.

cGMP and NHR signaling co-regulate expression of insulin-like peptides and developmental activation of infective larvae in Strongyloides stercoralis

The infectious form of the parasitic nematode Strongyloides stercoralis is a developmentally arrested third-stage larva (L3i), which is morphologically similar to the developmentally arrested dauer larva in the free-living nematode Caenorhabditis elegans. We hypothesize that the molecular pathways regulating C. elegans dauer development also control L3i arrest and activation in S. stercoralis. This study aimed to determine the factors that regulate L3i activation, with a focus on G protein-coupled receptor-mediated regulation of cyclic guanosine monophosphate (cGMP) pathway signaling, including its modulation of the insulin/IGF-1-like signaling (IIS) pathway. We found that application of the membrane-permeable cGMP analog 8-bromo-cGMP potently activated development of S. stercoralis L3i, as measured by resumption of feeding, with 85.1 ± 2.2% of L3i feeding in 200 µM 8-bromo-cGMP in comparison to 0.6 ± 0.3% in the buffer diluent. Utilizing RNAseq, we examined L3i stimulated with DMEM, 8-bromo-cGMP, or the DAF-12 nuclear hormone receptor (NHR) ligand Δ7-dafachronic acid (DA)--a signaling pathway downstream of IIS in C. elegans. L3i stimulated with 8-bromo-cGMP up-regulated transcripts of the putative agonistic insulin-like peptide (ILP) -encoding genes Ss-ilp-1 (20-fold) and Ss-ilp-6 (11-fold) in comparison to controls without stimulation. Surprisingly, we found that Δ7-DA similarly modulated transcript levels of ILP-encoding genes. Using the phosphatidylinositol-4,5-bisphosphate 3-kinase inhibitor LY294002, we demonstrated that 400 nM Δ7-DA-mediated activation (93.3 ± 1.1% L3i feeding) can be blocked using this IIS inhibitor at 100 µM (7.6 ± 1.6% L3i feeding). To determine the tissues where promoters of ILP-encoding genes are active, we expressed promoter::egfp reporter constructs in transgenic S. stercoralis post-free-living larvae. Ss-ilp-1 and Ss-ilp-6 promoters are active in the hypodermis and neurons and the Ss-ilp-7 promoter is active in the intestine and a pair of head neurons. Together, these data provide evidence that cGMP and DAF-12 NHR signaling converge on IIS to regulate S. stercoralis L3i activation.

Serotonin signaling in Schistosoma mansoni: a serotonin-activated G protein-coupled receptor controls parasite movement

Serotonin is an important neuroactive substance in all the parasitic helminths. In Schistosoma mansoni, serotonin is strongly myoexcitatory; it potentiates contraction of the body wall muscles and stimulates motor activity. This is considered to be a critical mechanism of motor control in the parasite, but the mode of action of serotonin is poorly understood. Here we provide the first molecular evidence of a functional serotonin receptor (Sm5HTR) in S. mansoni. The schistosome receptor belongs to the G protein-coupled receptor (GPCR) superfamily and is distantly related to serotonergic type 7 (5HT7) receptors from other species. Functional expression studies in transfected HEK 293 cells showed that Sm5HTR is a specific serotonin receptor and it signals through an increase in intracellular cAMP, consistent with a 5HT7 signaling mechanism. Immunolocalization studies with a specific anti-Sm5HTR antibody revealed that the receptor is abundantly distributed in the worm's nervous system, including the cerebral ganglia and main nerve cords of the central nervous system and the peripheral innervation of the body wall muscles and tegument. RNA interference (RNAi) was performed both in schistosomulae and adult worms to test whether the receptor is required for parasite motility. The RNAi-suppressed adults and larvae were markedly hypoactive compared to the corresponding controls and they were also resistant to exogenous serotonin treatment. These results show that Sm5HTR is at least one of the receptors responsible for the motor effects of serotonin in S. mansoni. The fact that Sm5HTR is expressed in nerve tissue further suggests that serotonin stimulates movement via this receptor by modulating neuronal output to the musculature. Together, the evidence identifies Sm5HTR as an important neuronal protein and a key component of the motor control apparatus in S. mansoni.

From lipid second messengers to molecular motors: microtubule-organizing center reorientation in T cells

In T lymphocytes, polarization of the microtubule-organizing center (MTOC) to the immunological synapse enables the directional secretion of cytokines, cytolytic factors, and other soluble molecules toward the antigen-presenting cell. This is likely to be crucial for maintaining the specificity of T-cell effector responses. Here, we review recent advances in our understanding of MTOC reorientation in T cells, focusing first on the importance of diacylglycerol and protein kinase C isozymes and then on the molecular motor proteins that function downstream to drive MTOC movement.

Acute peripheral tissue effects of ghrelin on interstitial levels of glucose, glycerol, and lactate: a microdialysis study in healthy human subjects

Ghrelin is a gut-derived peptide and an endogenous ligand for the ghrelin receptor. Intravenous infusion of ghrelin induces insulin resistance and hyperglycemia and increases circulating levels of nonesterified free fatty acids. Our objective was to investigate whether the metabolic effects are mediated directly by ghrelin in skeletal muscle and adipose (peripheral and central) tissues. Ten healthy men (24.9 ± 1.3 yr) received 300 min of supraphysiological ghrelin administration by microdialysis catheters in skeletal muscle and adipose tissues in a randomized, single-blind, and placebo-controlled study. Microdialysis perfusates were analyzed every 30 min for glucose, glycerol, and lactate during both a basal period and a hyperinsulinemic euglycemic clamp. The primary outcome measures were interstitial concentrations of glucose, glycerol, and lactate in skeletal muscle and adipose tissues. Interstitial concentrations of glucose were similar in skeletal muscle, peripheral, and central adipose tissue in the basal period. During hyperinsulinemia, interstitial concentrations of glucose in skeletal muscle decreased in response to ghrelin exposure [2.84 ± 0.25 (ghrelin) vs. 3.06 ± 0.26 mmol/l (placebo), P = 0.04]. Ghrelin exposure did not impact on interstitial concentrations of glycerol and lactate. We conclude that ghrelin administration into skeletal muscle decreases interstitial concentrations of glucose during euglycemic hyperinsulinemia, which is indicative of increased insulin sensitivity without any effects on interstitial glycerol levels in either muscle or adipose tissue. These data contrast with the metabolic effects of ghrelin observed after systemic exposure and suggest the existence of a second messenger that remains to be identified.

PtdIns5P and Pin1 in oxidative stress signaling

Oxidative signaling is important in cellular health, involved in aging and contributes to the development of several diseases such as cancer, neurodegeneration and diabetes. Correct management of reactive oxygen species (ROS) prevents oxidative stress within cells and is imperative for cellular wellbeing. A key pathway that is regulated by oxidative stress is the activation of proline-directed stress kinases (p38, JNK). Phosphorylation induced by these kinases is often translated into cellular outcome through the recruitment of the prolyl-isomerase Pin1. Pin1 binds to phosphorylated substrates using its WW-domain and can induce conformational changes in the target protein through its prolyl-isomerase activity. We show that exposure of cells to UV irradiation or hydrogen peroxide (H₂O₂), induces the synthesis of the phosphoinositide second messenger PtdIns5P in part by inducing the interaction between phosphatidylinositol-5-phosphate 4-kinase (PIP4K) enzymes that remove PtdIns5P, with Pin1. In response to H₂O₂ exposure, Murine Embryonic Fibroblasts (MEFs) derived from Pin1⁻/⁻ mice showed increased cell viability and an increased abundance of PtdIns5P compared to wild-type MEFs. Decreasing the levels of PtdIns5P in Pin1⁻/⁻ MEFs decreased both their viability in response to H₂O₂ exposure and the expression of genes required for cellular ROS management. The decrease in the expression of these genes manifested itself in the increased accumulation of cellular ROS. These data strongly argue that PtdIns5P acts as a stress-induced second messenger that can calibrate how cells manage ROS.

Sphingosine-1-phosphate: distribution, metabolism and role in the regulation of cellular functions

The role of sphingosine-1-phosphate (S1P) in regulation of cellular functions and cell protection is reviewed. S1P, along with other sphingolipid metabolites, is believed to act as an intracellular second messenger and as an extracellular mediator molecule. S1P chemistry, production and metabolism are described. Cellular receptors for S1P and their tissue specificity are described. Platelets and erythrocytes have a crucial significance in blood transport of S1P. Hypoxic conditions induce an increase in S1P, which initiates a set of cytoprotective events via its cellular receptors. S1P involvement in regulation of cell migration, myogenesis, control of skeletal muscle function is described. It is shown that S1P balance disturbances may mediate pathological state. S1P system implication in regulation of the most important cellular functions allows considering it as a prospective remedial target.

Ceramide function in the brain: when a slight tilt is enough

Ceramide, the precursor of all complex sphingolipids, is a potent signaling molecule that mediates key events of cellular pathophysiology. In the nervous system, the sphingolipid metabolism has an important impact. Neurons are polarized cells and their normal functions, such as neuronal connectivity and synaptic transmission, rely on selective trafficking of molecules across plasma membrane. Sphingolipids are abundant on neural cellular membranes and represent potent regulators of brain homeostasis. Ceramide intracellular levels are fine-tuned and alteration of the sphingolipid-ceramide profile contributes to the development of age-related, neurological and neuroinflammatory diseases. The purpose of this review is to guide the reader towards a better understanding of the sphingolipid-ceramide pathway system. First, ceramide biology is presented including structure, physical properties and metabolism. Second, we describe the function of ceramide as a lipid second messenger in cell physiology. Finally, we highlight the relevance of sphingolipids and ceramide in the progression of different neurodegenerative diseases.

Phosphoinositide 3-kinase γ mediates microglial phagocytosis via lipid kinase-independent control of cAMP

Microglial phagocytosis plays a key role in neuroprotective and neurodegenerative responses of the innate immune system in the brain. Here we investigated the regulatory function of phosphoinositide 3-kinase γ (PI3Kγ) in phagocytosis of bacteria and Zymosan particles by mouse brain microglia in vitro and in vivo. Using genetic and pharmacological approaches our data revealed PI3Kγ as an essential mediator of microglial phagocytosis. Unexpectedly, microglia expressing lipid kinase deficient mutant PI3Kγ exhibited similar phagocytosis as wild-type cells. These data suggest kinase-independent stimulation of cAMP phosphodiesterase activity by PI3Kγ as a crucial mediator of phagocytosis. In sum our findings indicate PI3Kγ-dependent suppression of cAMP signaling as a critical regulatory element of microglial phagocytosis.

Insulin receptor regulates photoreceptor CNG channel activity

Photoreceptor cyclic nucleotide gated (CNG) channels are critical elements in phototransduction and light adaptation. Here we report that insulin receptor (IR), an integral membrane protein, directly phosphorylates the CNGA1 subunit of CNG channels that in turn affects the function of these channels negatively. The IR phosphorylates Tyr(498) and Tyr(503) residues on CNGA1 that are situated at the membrane-cytoplasmic interface. The IR tyrosine kinase activity is essential for the inhibition of CNG channel. To maintain the channels in an off state, it is necessary not only to have a precise balance of the cGMP levels but also to have a control on the cGMP sensitivity of the CNG channels itself. In this study, we observed that the channel opens at a lower concentration of cGMP in IR(-/-) mice. These studies suggest that IR regulates the modulation of CNG channel activity in vivo.

Roles of cADPR and NAADP in pancreatic cells

Cyclic ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP) are Ca(2+)-mobilizing nucleotides that were discovered in the late 1980s. Two decades of investigations have built up a considerable understanding about these two molecules that are related because both are derived from pyridine nucleotides and known to be generated by CD38/ADP-ribosyl cyclases. cADPR has been shown to target the ryanodine receptors in the endoplasmic reticulum whereas NAADP stimulates the two-pore channels in the endo-lysosomes. Accumulating results indicate that cADPR and NAADP are second messenger molecules mediating Ca(2+) signaling activated by a wide range of agonists. This article reviews what is known about these two molecules, especially regarding their signaling roles in the pancreatic cells.

Calcium signals induced by FGF-2 in parasympathetic neurons: role of second messenger pathways

Basic Fibroblast Growth Factor, or FGF-2, has been shown to promote neuronal survival and neurite outgrowth in dissociated neurons from the embryonic chick ciliary ganglion; in these effects the three main signal transduction pathways downstream the activated FGFR receptor, i.e. the MAPK, the PI3-K and the PLCγ ones, are differentially involved. While it has been shown that FGF-2 can elicit long lasting elevations in intracellular calcium concentration, [Ca(2+)](i), the role of the three pathways in this process has not been elucidated. Here we show, by means of pharmacological inhibitors, that all three are involved, at a different extent, in the generation of the [Ca(2+)](i) increase induced by FGF-2; in particular, inhibition of the PLCγ pathway, in addition to reducing the number of responsive cells, induces, in a significant population of cells, basal calcium oscillations in the absence of the growth factor and interferes with calcium signals elicited by depolarization. We propose that this complex behaviour can be due to a perturbation in PIP(2) levels at the plasmamembrane.

New paradigms in cAMP signalling

Signalling through adenosine 3'5' monophosphate (cAMP) is known to be important in virtually every cell. The mapping of the human genome over the past two decades has revealed an unexpected complexity of cAMP signalling, which is shared from insects to mammals. A more recent technical advance is the ability to monitor intracellular cAMP levels at subcellular spatial resolution within the time-domains of fast biochemical reactions. Thus, new light has been shed on old paradigms, some of which turn out to be multiple new ones. The novel aspects of cAMP signalling are highlighted here: (1) agonist induced plasticity - showing how the repertory of cAMP signalling genes supports homeostatic adaptation; (2) sustained cAMP signalling after endocytosis; (3) pre-assembled receptor-Gs-adenylyl cyclase complexes. Finally, a hypothetical model of propagating neuronal cAMP signals travelling form dendrites to the cell body is presented.