The cAMP effector EPAC activates Elk1 transcription factor in prostate smooth muscle, and is a minor regulator of α1-adrenergic contraction

Abstract

BackgroundProstate smooth muscle tone is regulated by α1-adrenoceptor-induced contraction and cAMP-mediated relaxation. EPAC is an effector of cAMP, being involved in smooth muscle relaxation and cell cycle control outside the lower urinary tract. Here, we investigated the expression and function of EPAC in human prostate tissues from patients undergoing radical prostatectomy.ResultsmRNA and protein expression of EPAC was detected in all prostate tissues by RT-PCR and Western blot analysis. Immunoreactivity was observed in stromal cells, and colocalized with immunofluorescence for α-smooth muscle actin and calponin. Under normal conditions, noradrenaline- or phenylephrine-induced contraction of prostate strips in the organ bath was not affected by the EPAC activator pCPT (SP-8-pCPT-2′-O-Me-cAMPS.NA) (30 μM). However, when the cyclooxygenase inhibitor indomethacin (50 μM) was added, EPAC activators pCPT and OME (8-CPT-2′-O-Me-cAMP.Na) (30 μM) significantly reduced contractions by low concentrations of phenylephrine. These effects were not observed on noradrenaline-induced contraction. OME and pCPT caused phosphorylation of the transcription factor Elk1 in prostate tissues. Elk1 activation was confirmed by EMSA (electrophoretic mobility shift assay), where OME and pCPT incresed Elk1 binding to a specific DNA probe.ConclusionsEPAC activation may reduce α1-adrenergic prostate contraction in the human prostate, although this effect is masked by cyclooxygenases and β-adrenoceptors. A main EPAC function in the human prostate may be the regulation of the transcription factor Elk1.

Intracellular cAMP Sensor EPAC: Physiology, Pathophysiology, and Therapeutics Development

“…Direct activation of EPAC did in fact reduce phenylephrine-induced contraction, but only in the presence of the cyclooxygenase (COX) inhibitor indomethacin, and no observable activity was detected after norepinephrine treatment regardless of COX inhibition. Potentially, this represents a masking effect where EPAC is maximally activated following COX or ␤-AR induction of cAMP; thus the action of EPAC is only observable after inhibition of these components (410). In agreement with the results in prostate, the role of EPAC in human detrusor smooth muscle revealed only a minor role for EPAC activation in relaxation when compared with PKA stimulation.…”

“…These results may be reflective of a more modulatory role of EPAC, compared with PKA, in physiological conditions, whereas the function of EPAC may be exemplified in times of stress for many smooth muscles groups. Although EPAC may only have a minor role in contraction in these muscles, the activation of EPAC was unexpectedly linked to transcriptional regulation through phosphorylation of Elk-1 in prostate which may indicate a connection between muscle tone and growth to be determined by future studies (410). Thus, as with other aspects of cAMP signaling that were initially reserved for PKA activation, further investigation is required to identify relevant and potentially alternative mechanisms that may involve EPAC modulation of these signaling systems.…”

Epac1 Is Crucial for Maintenance of Endothelial Barrier Function through A Mechanism Partly Independent of Rac1

“…In addition, a member of the E-twenty-six (ETS) family of transcription factors, Elk3, was shown to regulate the VE-cadherin gene expression, since Elk3 downregulation resulted in increased VE-cadherin expression [ 38 ]. Moreover, it was reported that Epac1 can control transcription factor activity of another ETS family member—Elk1 [ 39 ], potentially modulating the protein expression. We therefore tested if deletion of Epac1 could alter VE-cadherin expression using RT-PCR and WB analyses.…”

Revisiting the roles of cAMP signalling in the progression of prostate cancer

“…EPAC1 is in its active state when bound to cAMP and its effector Rap1b. EPAC1 and EPAC2 are expressed in all prostate cells of patients undergoing radical prostatectomy and expression levels appear to vary along with PSA [ 94 ]. EPAC expression appears to be colocalised with αSMA, a marker of smooth muscle cells.…”