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cAMP Signalling (camp + signalling)
Selected AbstractsRole for cAMP-protein kinase A signalling in augmented neutrophil adhesion and chemotaxis in sickle cell diseaseEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2007Andreia A. Canalli Abstract The significance of the leukocyte in sickle cell disease (SCD) pathophysiology is becoming increasingly recognised; we sought to examine whether the chemotactic properties of neutrophils of SCD individuals may be altered and, further, to better understand the signalling events that mediate altered SCD neutrophil function. Adhesion to immobilised fibronectin (FN) and chemotaxis of control and SCD neutrophils were assessed using in vitro static adhesion assays and 96-well chemotaxis chamber assays. Adhesion assays confirmed a significantly higher basal adhesion of SCD neutrophils to FN, compared with control neutrophils. Chemotaxis assays established, for the first time, that SCD neutrophils demonstrate greater spontaneous migration and, also, augmented migration in response to IL-8, when compared with control neutrophils. Co-incubation of SCD neutrophils with KT5720 (an inhibitor of PKA) abrogated increased basal SCD neutrophil adhesion, spontaneous chemotaxis and IL-8-stimulated chemotaxis. Stimulation of SCD neutrophils with IL-8 also significantly augmented SCD neutrophil adhesion to FN with a concomitant increase in cAMP levels and this increase in adhesion was abolished by KT5720. Interestingly, the adhesive properties of neutrophils from SCD individuals on hydroxyurea therapy were not significantly altered and results indicate that a reduction in intracellular cAMP may contribute to lower the adhesive properties of these cells. Data indicate that up-regulated cAMP signalling plays a significant role in the altered adhesive and migratory properties in SCD neutrophils. Such alterations may have important implications for the pathophysiology of the disease and the cAMP-PKA pathway may represent a therapeutic target for the abrogation of altered leukocyte function. [source] The role of hexose transport and phosphorylation in cAMP signalling in the yeast Saccharomyces cerevisiaeFEMS YEAST RESEARCH, Issue 1 2001Filip Rolland Abstract Glucose-induced cAMP signalling in Saccharomyces cerevisiae requires extracellular glucose detection via the Gpr1-Gpa2 G-protein coupled receptor system and intracellular glucose-sensing that depends on glucose uptake and phosphorylation. The glucose uptake requirement can be fulfilled by any glucose carrier including the Gal2 permease or by intracellular hydrolysis of maltose. Hence, the glucose carriers do not seem to play a regulatory role in cAMP signalling. Also the glucose carrier homologues, Snf3 and Rgt2, are not required for glucose-induced cAMP synthesis. Although no further metabolism beyond glucose phosphorylation is required, neither Glu6P nor ATP appears to act as metabolic trigger for cAMP signalling. This indicates that a regulatory function may be associated with the hexose kinases. Consistently, intracellular acidification, another known trigger of cAMP synthesis, can bypass the glucose uptake requirement but not the absence of a functional hexose kinase. This may indicate that intracellular acidification can boost a downstream effect that amplifies the residual signal transmitted via the hexose kinases when glucose uptake is too low. [source] Autocrine growth factors in human periodontal ligament cells cultured on enamel matrix derivativeJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 2 2001Staale P. Lyngstadaas Abstract Objective: Enamel extracellular matrix proteins in the form of the enamel matrix derivative EMDOGAINŽ (EMD) have been successfully employed to mimic natural cementogenesis to restore fully functional periodontal ligament, cementum and alveolar bone in patients with severe periodontitis. When applied to denuded root surfaces EMD forms a matrix that locally facilitates regenerative responses in the adjacent periodontal tissues. The cellular mechanism(s), e.g. autocrine growth factors, extracellular matrix synthesis and cell growth, underlying PDL regeneration with EMD is however poorly investigated. Material and Methods: Human periodontal ligament (PDL) cells were cultured on EMD and monitored for cellular attachment rate, proliferation, DNA replication and metabolism. Furthermore, intracellular cyclic-AMP levels and autocrine production of selected growth factors were monitored by immunological assays. Controls included PDL and epithelial cells in parallel cultures. Results: PDL cell attachment rate, growth and metabolism were all significantly increased when EMD was present in cultures. Also, cells exposed to EMD showed increased intracellular cAMP signalling and autocrine production of TGF-,1, IL-6 and PDGF AB when compared to controls. Epithelial cells increased cAMP and PDGF AB secretion when EMD was present, but proliferation and growth were inhibited. Conclusion: Cultured PDL cells exposed to EMD increase attachment rate, growth rate and metabolism, and subsequently release several growth factors into the medium. The cellular interaction with EMD generates an intracellular cAMP signal, after which cells secrete TGF-,1, IL-6 and PDGF AB. Epithelial cell growth however, is inhibited by the same signal. This suggest that EMD favours mesenchymal cell growth over epithelium, and that autocrine growth factors released by PDL cells exposed to EMD contribute to periodontal healing and regeneration in a process mimicking natural root development. [source] Calmodulin activity and cAMP signalling modulate growth and apical secretion in pollen tubesTHE PLANT JOURNAL, Issue 6 2004Cláudia Rato Summary Our present understanding implicates both calmodulin (CaM) and 3,,5,-cyclicAMP (cAMP) in the regulation of pollen tube growth. However, downstream molecules of these signalling pathways and the cellular processes they modulate remain largely unknown. In order to elucidate the role of CaM, we mapped its activity in growing pollen tubes. 2-chloro-(,-amino-Lys75)-[6-4-(N,N, -diethylaminophenyl)-1,3,5-triazin-4-yl]-calmodulin (TA-CaM) and fluorescein-calmodulin (FL-CaM), fluorescent analogues of CaM, were loaded into pollen tubes and CaM activity was mapped by fluorescence ratio imaging. It was found that CaM activity exhibits a tip-focused gradient, similar to the distribution of cytosolic-free calcium ([Ca2+]c). In long pollen tubes, apical CaM activity was also found to oscillate with a period similar to [Ca2+]c (40,80 sec). This oscillatory behaviour was not observed in small pollen tubes or in tubes that had stopped growing. Changes in CaM activity within the dome of the pollen tube apex resulting from the photolysis of caged photolysis of RS-20 (a peptide antagonist of CaM) induced re-orientation of the growth axis, suggesting that CaM is also involved in the guidance mechanism. CaM activity was strongly modulated by intracellular changes in cAMP (induced by activators and antagonists of adenylyl cyclase). These results indicate that the action of this protein is dependent not solely on [Ca2+]c but also on a cross-talk with other signalling pathways. A putative target of this cross-talk is the secretory machinery as observed in pollen tubes loaded with the FM (N -(3-triethylammoniumpropyl)-4-(4-dibutylamino)styryl)pyridinium dibromide 1-43 dye and exposed to different antagonists and activators of these molecules. Our data thus suggest that pollen tube growth and orientation depend on an intricate cross-talk between multiple signalling pathways in which CaM is a key element. [source] SPATIAL AND TEMPORAL ASPECTS OF cAMP SIGNALLING IN CARDIAC MYOCYTESCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 11 2008Radu V Iancu SUMMARY 1,1 -Adrenoceptor and M2 muscarinic receptor regulation of cAMP production plays a pivotal role in autonomic regulation of cardiac myocyte function. However, not all responses are easily explained by a uniform increase or decrease in cAMP activity throughout the entire cell. 2Adenovirus expression of fluorescence resonance energy transfer (FRET)-based biosensors can be used to monitor cAMP activity in protein kinase A (PKA) signalling domains, as well as the bulk cytoplasmic domain of intact adult cardiac myocytes. 3Data obtained using FRET-based biosensors expressed in different cellular microdomains have been used to develop a computational model of compartmentalized cAMP signalling. 4A systems biology approach that uses quantitative computational modelling together with experimental data obtained using FRET-based biosensors has been used to provide evidence for the idea that compartmentation of cAMP signalling is necessary to explain the stimulatory responses to ,1 -adrenoceptor activation as well as the complex temporal responses to M2 muscarinic receptor activation. [source] | |||||||||||||