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

Martin Hennenberg,Frank Strittmatter,Christian Gratzke,Sebastian Walther,Christian G Stief,Beata Rutz,Henning Schmetkamp

doi:10.1186/1423-0127-20-46

Martin Hennenberg, Frank Strittmatter + Show 5 more

Open Access

https://doi.org/10.1186/1423-0127-20-46

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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.

Highlights

Prostate smooth muscle tone is regulated by α1-adrenoceptor-induced contraction and cAMP-mediated relaxation
Hyperlasia is of utmost importance for benign prostate syndrom (BPS), exchange proteins directly activated by cAMP” (EPAC)-driven Elk1 activation has not been investigated in the prostate
Quantitative Real time polymerase chain reaction (RT-PCR) Expression of EPAC1 and EPAC2 mRNA was detected in prostate samples from all investigated patients (n=5)

Summary

Introduction

Prostate 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. EPACs represent a group of cAMP effectors, which mediate cAMP effects independently from PKA [11,13] Both isoforms, EPAC1 and EPAC2 were recently described from different cell types and organs, including smooth muscle outside the lower urinary tract [11,13,14,15,16]. Activation of EPACs by these activators caused relaxation of airway smooth muscle [16] Besides these motoric effects, EPAC activation by cAMP or specific activators results in activation of different transcription factors [17], which is involved in EPAC-mediated regulation of cell cycle [11,13,17]. Hyperlasia is of utmost importance for BPS, EPAC-driven Elk activation has not been investigated in the prostate

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