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Aims: Nitric oxide (NO) and atrial natriuretic peptide (ANP) signalling via cGMP controls smooth muscle tone. One important signalling pathway of cGMP-dependent protein kinase type I (cGKI) is mediated by IRAG (IP3 receptor associated cGKI substrate) which is highly expressed in smooth muscle tissues. To elucidate the role of IRAG for NO- and ANP-mediated smooth muscle tone regulation, cGKI localization, and for its possible function in blood pressure adjustment, we generated IRAG-knockout mice by targeted deletion of exon 3. [ABSTRACT FROM PUBLISHER]

An abstract of the article "IRAG is involved in NO/cGMP-mediated inhibition of platelet function," by Melanie Ant, Katja Sig, Christina Eigelsperger, Matthias Werner, Franz Hofmann and Jens Schlossmann is presented.

Abstract: cGMP-dependent kinase I (cGKI) is a major mediator of smooth muscle relaxation and exists in two isoforms, α and β. Both isoforms are supposed to mediate their effects via different intracellular signaling pathways. To verify this concept, the kinetics of relaxation mediated by either isoform was analyzed in gastric fundus smooth muscle from mice. Muscles from mice that express selectively the Iα or Iβ isoform of cGKI in smooth muscle (sm-cGKIα or sm-cGKIβ mice) were compared to muscles from conventional cGKI−/− mice. Fundus muscles were contracted by carbachol and then relaxed by 8-Br-cGMP or by electrical field stimulation (EFS). The time course of relaxation by 8-Br-cGMP was not different between muscles from sm-cGKIα and sm-cGKIβ mice. EFS induced a fast transient relaxation in muscles from sm-cGKIα and sm-cGKIβ mice that was blocked by the NO synthase inhibitor L-NAME. Recovery from this relaxation was about 4-times slower in muscles from sm-cGKIα mice than in muscles from sm-cGKIβ mice. The different kinetic of recovery from relaxation after EFS in sm-cGKIα and sm-cGKIβ mice suggests that different signaling pathways exist for each cGKI isoform in vivo in fundus muscles. [Copyright &y& Elsevier]

Introduction. The cyclic adenosine monophosphate-dependent protein kinase (cAK) is considered a key protein in the control of smooth muscle tone in the cardiovascular system. There is evidence that erectile dysfunction might be linked to systemic vascular disorders and arterial insufficiency, subsequently resulting in structural changes in the penile tissue. The expression and significance of cAK in human cavernous arteries (HCA) have not been evaluated. Aims. To evaluate the expression of cAK isoforms in HCA and examine the role of cAK in the cyclic adenosine monophosphate (cAMP)- and cyclic guanosine monophosphate (cGMP)-mediated control of penile vascular smooth muscle. Methods. The expression and distribution of phosphodiesterase type 4 (PDE4) and cAK isoforms in sections of HCA were investigated by means of immunohistochemistry and Western blot analysis. The effects of the cAK inhibitor Rp-8-CPT-cAMPS on the relaxation of isolated preparations of HCA (diameter > 100 µm) induced by rolipram, sildenafil, tadalafil, and vardenafil were studied using the organ bath technique. Main Outcome Measures. Investigate the expression of cAK in relation to α-actin and PDE4 in HCA and evaluate the effects of an inhibition of cAK on the relaxation induced by inhibitors of PDE4 and PDE5 of isolated penile arteries. Results. Immunosignals specific for cAKIα, IIα, and IIβ were observed within the wall of HCA. Double stainings revealed colocalization of cAK with α-actin and PDE4. The expression of cAK isoforms was confirmed by Western blot analysis. The reversion of tension induced by inhibitors of PDE4 and PDE5 of isolated penile vascular tissue were attenuated significantly by Rp-8-CPT-cAMPS. Conclusions. Our results demonstrate the expression of cAK isoforms in the smooth musculature of HCA and its colocalization with PDE4. A significant role for cAK in the regulation mediated by cAMP and cGMP of vascular smooth muscle tone in HCA can also be assumed. Waldkirch ES, Ückert S, Sigl K, Satzger I, Geismar U, Langnäse K, Richter K, Sohn M, Kuczyk MA, and Hedlund P. Expression of cyclic AMP-dependent protein kinase isoforms in human cavernous arteries: Functional significance and relation to phosphodiesterase type 4. J Sex Med 2010;7:2104–2111. [ABSTRACT FROM AUTHOR]

Introduction. Besides the bioavailability of nitric oxide (NO), downstream guanine monophosphate (cGMP) effector proteins are also considered to play a significant role in penile vascular disease. In animal studies, a downregulation of the cGMP-dependent protein kinase-1 (cGKI) α isoform has been linked to erectile dysfunction and diabetes mellitus. So far, the expression of cGKI α and β isoforms has not been evaluated in human penile erectile tissue. Aim. To evaluate the expression of cGKI α and β isoforms in relation to smooth muscle α-actin, cGMP, and endothelial NO synthase (eNOS) in human cavernous arteries (HCAs) and human corpus cavernosum (HCC). Methods. Cryostat sections of HCA and HCC were incubated with primary antibodies directed against α-actin, cGMP, eNOS, cGKI, cGKI α, and cGKI β. Visualization of double-labeled immunofluorescent stainings was achieved by laser microscopy. Western blot analysis was performed in order to confirm the expression of cGKI isoforms. Main Outcome Measures. Expression of cGKI α and β isoforms in relation to smooth muscle α-actin, cGMP, and eNOS in human penile erectile tissue. Results. Immunoreactivities specific for cGKI, cGKI α, and cGKI β were observed within the smooth musculature and the endothelium of cavernous arteries and sinusoids. Double stainings revealed the colocalization of alpha-actin, cGMP, eNOS, and cGKI isoforms. The expression of cGKI isoforms was confirmed by Western blot analysis. Conclusions. Our results demonstrate, for the first time, the expression of both cGKI α and β isoforms in the smooth musculature of HCA and HCC. Corresponding to recent findings from animal studies, the presence of cGKI α and β provides further evidence for a significant role of these enzymes in the control of smooth muscle function in human penile erectile tissue. Waldkirch E, Uckert S, Sigl K, Imkamp F, Langnaese K, Richter K, Jonas U, Sohn M, Stief C, Wolf G, and Hedlund P. Expression and distribution of cyclic GMP-dependent protein kinase-1 isoforms in human penile erectile tissue. J Sex Med 2008;5:536–543. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the expression of isoforms of the cyclic AMP (cAMP)–dependent protein kinase (cAK) in the transition zone of the human prostate and the functional significance of the enzyme in the control of prostate smooth muscle. Methods: Using Western blot analysis and immunohistochemistry, the expression and distribution in the prostate of cAKIα, cAKIβ, cAKIIα, and cAKIIβ in relation to α-actin and the phosphodiesterase PDE4 (types A and B) were investigated. The effects of the cAK inhibitor Rp-8-CPT-cAMPS on the reversion of the adrenergic tension of isolated prostate tissue induced by forskolin, rolipram, sodium nitroprusside (SNP), and tadalafil were examined by means of the organ bath technique. Results: Immunosignals specific for cAKIα, cAKIIα, and cAKIIβ were observed in the smooth musculature and glandular structures of the prostate. Double stainings revealed the colocalization of α-actin and PDE4 with the cAK isoforms. The expression of the cAK isoforms was confirmed by Western blot analysis. The relaxation of the tension induced by norepinephrine brought about by forskolin, rolipram, SNP, and tadalafil was significantly attenuated by Rp-8-CPT-cAMPS. Conclusions: The colocalization of smooth muscle α-actin and PDE4 with cAK, as well as the results from the organ bath experiments, provide further evidence for a pivotal role of the cAMP-dependent signaling in the regulation of prostate smooth muscle contractility. Compounds interacting with the cAMP/cAK pathway might represent a new therapeutic avenue to treat symptoms of benign prostatic hyperplasia and lower urinary tract symptomatology. [ABSTRACT FROM AUTHOR]