Epac is a Rap1 guanine-nucleotide-exchange factor directly activated by cyclic AMP

Rooij, Johan de; Zwartkruis, Fried; Verheijen, Mark H. G.; Cool, Robbert H.; Nijman, Sebastian M.; Wittinghofer, Alfred; Bos, Johannes L.

doi:10.1038/24884

Cited by 1,791 publications

(1,682 citation statements)

References 26 publications

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“…Apart from the prototypical cAMP dependent protein kinase PKA, Epac proteins (also known as Rap guanine nucleotide exchange factors) have recently been implicated as novel mediators of cAMP [36]. To investigate whether Epac1 and Epac2 were expressed and functional in chondrifying HDC, further experiments were carried out.…”

Section: Basal Epac Activity Could Be a Negative Regulator Of Chondromentioning

confidence: 99%

Mechanical loading stimulates chondrogenesis via the PKA/CREB-Sox9 and PP2A pathways in chicken micromass cultures

Juhász

Matta

Somogyi

et al. 2014

Cellular Signalling

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Biomechanical stimuli play important roles in the formation of articular cartilage during early foetal life, and optimal mechanical load is a crucial regulatory factor of adult chondrocyte metabolism and function. In this study, we undertook to analyse mechanotransduction pathways during in vitro chondrogenesis. Chondroprogenitor cells isolated from limb buds of 4-day-old chicken embryos were cultivated as high density cell cultures for 6 days. Mechanical stimulation was carried out by a self-designed bioreactor that exerted uniaxial intermittent cyclic load transmitted by the culture medium as hydrostatic pressure and fluid shear to differentiating cells. The loading scheme (0.05 Hz, 600 Pa; for 30 min) was applied on culturing days 2 and 3, when final commitment and differentiation of chondroprogenitor cells occurred in this model. The applied mechanical load significantly augmented cartilage matrix production and elevated mRNA expression of several cartilage matrix constituents, including collagen type II and aggrecan core protein, as well as matrixproducing hyaluronan synthases through enhanced expression, phosphorylation and nuclear signals of the main chondrogenic transcription factor Sox9. Along with increased cAMP levels, a significantly enhanced protein kinase A (PKA) activity was also detected and CREB, the archetypal downstream transcription factor of PKA signalling, exhibited elevated phosphorylation levels and stronger nuclear signals in response to mechanical stimuli. All the above effects were diminished by the PKA-inhibitor H89. Inhibition of the PKA-independent cAMP-mediators Epac1 and Epac2 with HJC0197 resulted in enhanced cartilage formation, which was additive to that of the mechanical stimulation, implying that the chondrogenesispromoting effect of mechanical load was independent of Epac. At the same time, PP2A activity was reduced following mechanical load and treatments with the PP2A-inhibitor okadaic acid were able to mimic the effects of the intervention. Our results indicate that proper mechanical stimuli augment in vitro cartilage formation via promoting both Juhász and Matta et al. 3 differentiation and matrix production of chondrogenic cells, and the opposing regulation of the PKA/CREB-Sox9 and the PP2A signalling pathways is crucial in this phenomenon.

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Section: Basal Epac Activity Could Be a Negative Regulator Of Chondromentioning

confidence: 99%

Mechanical loading stimulates chondrogenesis via the PKA/CREB-Sox9 and PP2A pathways in chicken micromass cultures

Juhász

Matta

Somogyi

et al. 2014

Cellular Signalling

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“…Therefore, if the protective cAMP‐related signalling mechanisms can be activated without stimulation of β‐adrenoceptors, this would give a significant therapeutic advantage. Although most of the biological effects of cAMP on the heart have been assigned to PKA (Bers, 2007), cAMP also activates Epac (a guanine nucleotide exchange protein directly activated by cAMP) (de Rooij et al, 1998). The cAMP/Epac pathway is independent of and parallel to the cAMP/PKA signalling pathway (Pereira et al, 2012; Okumura et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Functional and cardioprotective effects of simultaneous and individual activation of protein kinase A and Epac

Khaliulin

Bond

James

et al. 2017

British J Pharmacology

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Background and PurposeMyocardial cAMP elevation confers cardioprotection against ischaemia/reperfusion (I/R) injury. cAMP activates two independent signalling pathways, PKA and Epac. This study investigated the cardiac effects of activating PKA and/or Epac and their involvement in cardioprotection against I/R.Experimental ApproachHearts from male rats were used either for determination of PKA and PKC activation or perfused in the Langendorff mode for either cardiomyocyte isolation or used to monitor functional activity at basal levels and after 30 min global ischaemia and 2 h reperfusion. Functional recovery and myocardial injury during reperfusion (LDH release and infarct size) were evaluated. Activation of PKA and/or Epac in perfused hearts was induced using cell permeable cAMP analogues in the presence or absence of inhibitors of PKA, Epac and PKC. H9C2 cells and cardiomyocytes were used to assess activation of Epac and effect on Ca2+ transients.Key ResultsSelective activation of either PKA or Epac was found to trigger a positive inotropic effect, which was considerably enhanced when both pathways were simultaneously activated. Only combined activation of PKA and Epac induced marked cardioprotection against I/R injury. This was accompanied by PKCε activation and repressed by inhibitors of PKA, Epac or PKC.Conclusion and ImplicationsSimultaneous activation of both PKA and Epac induces an additive inotropic effect and confers optimal and marked cardioprotection against I/R injury. The latter effect is mediated by PKCε activation. This work has introduced a new therapeutic approach and targets to protect the heart against cardiac insults.

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“…Increased intracellular cAMP levels directly activate the nucleotide exchange proteins directly activated by cAMP (Epacs or cAMP-GEFs) [34], which helps explain PKA-independent effects of cAMP on endothelial permeability. Epac1 and Epac2 splice variants contain a cAMP-binding domain and are capable of activating small GTPase Rap1 in a cAMP-dependent, PKA-independent manner [35].…”

Section: Introductionmentioning

confidence: 99%

Prostaglandins PGE2 and PGI2 promote endothelial barrier enhancement via PKA- and Epac1/Rap1-dependent Rac activation

Birukova

Zagranichnaya

et al. 2007

Experimental Cell Research

264

267

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Prostaglandin E 2 (PGE 2 ) and prostacyclin are lipid mediators produced by cyclooxygenase and implicated in the regulation of vascular function, wound repair, inflammatory processes, and acute lung injury. Although protective effects of these prostaglandins (PGs) are associated with stimulation of intracellular cAMP production, the crosstalk between cAMP-activated signal pathways in the regulation of endothelial cell (EC) permeability is not well understood. We studied involvement of cAMP-dependent kinase (PKA), cAMP-Epac-Rap1 pathway, and small GTPase Rac in the PGsinduced EC barrier protective effects and cytoskeletal remodeling. PGE 2 and PGI 2 synthetic analog beraprost increased transendothelial electrical resistance and decreased dextran permeability, enhanced peripheral F-actin rim and increased intercellular adherens junction areas reflecting EC barrier-protective response. Furthermore, beraprost dramatically attenuated thrombin-induced Rho activation, MLC phosphorylation and EC barrier dysfunction. In vivo, beraprost attenuated lung barrier dysfunction induced by high tidal volume mechanical ventilation. Both PGs caused cAMPmediated activation of PKA-, Epac/Rap1-and Tiam1/Vav2-dependent pathways of Rac1 activation and EC barrier regulation. Knockdown of Epac, Rap1, Rac-specific exchange factors Tiam1 and Vav2 using siRNA approach, or inhibition of PKA activity decreased Rac1 activation and PGinduced EC barrier enhancement. Thus, our results show that barrier-protective effects of PGE 2 and prostacyclin on pulmonary EC are mediated by PKA and Epac/Rap pathways, which converge on Rac activation and lead to enhancement of peripheral actin cytoskeleton and adherens junctions. These mechanisms may mediate protective effects of PGs against agonist-induced lung vascular barrier dysfunction in vitro and against mechanical stress-induced lung injury in vivo.

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Epac is a Rap1 guanine-nucleotide-exchange factor directly activated by cyclic AMP

Cited by 1,791 publications

References 26 publications

Mechanical loading stimulates chondrogenesis via the PKA/CREB-Sox9 and PP2A pathways in chicken micromass cultures

Mechanical loading stimulates chondrogenesis via the PKA/CREB-Sox9 and PP2A pathways in chicken micromass cultures

Functional and cardioprotective effects of simultaneous and individual activation of protein kinase A and Epac

Prostaglandins PGE2 and PGI2 promote endothelial barrier enhancement via PKA- and Epac1/Rap1-dependent Rac activation

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