SPATIAL AND TEMPORAL ASPECTS OF cAMP SIGNALLING IN CARDIAC MYOCYTES

Abstract

1. beta(1)-Adrenoceptor and M(2) 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. 2. Adenovirus 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. 3. Data obtained using FRET-based biosensors expressed in different cellular microdomains have been used to develop a computational model of compartmentalized cAMP signalling. 4. A 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 beta(1)-adrenoceptor activation as well as the complex temporal responses to M(2) muscarinic receptor activation.

Muscarinic receptors stimulate AC2 by novel phosphorylation sites, whereas Gβγ subunits exert opposing effects depending on the G-protein source

“…( n =30–60). ( D ) The 4 min area under the curve from ( C ) ( E ) The cAMP ratios were converted into cAMP concentration using in vitro parameters F abs , EC 50 and n H according to [23] as described previously [35]. ( F ) The basal cAMP concentrations and maximal stimulation or inhibition values in ( E ) were compared.…”

“…By calibrating the Epac2-camps sensors according to a previously described method [23,35], it was possible to approximately compare the absolute cAMP concentrations achieved by the various AC2 mutants. Stimulation with 10 μM CCh (at 60 s) transiently elicited a cAMP concentration of ~1.3 μM in cells stably expressing AC2 or T1057A (Figure 4E).…”

Agonist-Specific Compartmentation of cGMP Action in Myometrium

“…The notion that the action of soluble messengers such as cyclic nucleotides can subserve their signaling roles in an agonist-specific fashion was first proven more than 25 years ago for cAMP and is now well known for explaining signaling in cardiac muscle (Brunton et al, 1981;Buxton and Brunton, 1983;Iancu et al, 2007Iancu et al, , 2008a. Compartmentation of cGMP action has received less attention but has been suggested to explain the cGMP-independent effects of NO in smooth muscle (Buxton, 2004) and has been described in the heart Fischmeister et al, 2006).…”

Adenylyl cyclase AC8 directly controls its micro-environment by recruiting the actin cytoskeleton in a cholesterol-rich milieu

“…Substantial evidence has established that cAMP 'microdomains' exist, which facilitate discrimination in signal propagation (Bacskai et al, 1993;Buxton and Brunton, 1983;Iancu et al, 2008;Jurevicius and Fischmeister, 1996;Rich et al, 2000;Zaccolo and Pozzan, 2002). These microdomains are partially achieved by scaffolded phosphodiesterases (PDEs), which, by degrading cAMP at specific locations, limit its intracellular diffusion (Lynch et al, 2007;Nikolaev et al, 2006;Willoughby et al, 2006).…”