Rapid regulation of PDE-2 and PDE-4 cyclic AMP phosphodiesterase activity following ligation of the T cell antigen receptor on thymocytes: analysis using the selective inhibitors erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA) and rolipram

Michie, A. M. , Lobban, M., Müller, T., Harnett, M. M. and Houslay, M. D. (1996) Rapid regulation of PDE-2 and PDE-4 cyclic AMP phosphodiesterase activity following ligation of the T cell antigen receptor on thymocytes: analysis using the selective inhibitors erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA) and rolipram. Cellular Signalling, 8(2), pp. 97-110. (doi: 10.1016/0898-6568(95)02032-2)

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Abstract

The PDE2, cyclic GMP-stimulated, and the PDE4, cyclic AMP-specific enzymes provide the major, detectable cyclic AMP phosphodiesterase activities in murine thymocytes. In the absence of cyclic GMP, PDE4 activity predominated (∼80% total) but in the presence of low (10 μM) cyclic GMP concentrations, PDE2 activity constituted the major PDE activity in thymocytes (∼80% total). The PDE4 selective inhibitor rolipram dose-dependently inhibited thymocyte PDE4 activity (ic50 ∼ 65 nM). PDE2 was dose-dependently activated (ec50 ∼ 1 μM) by cyclic GMP and inhibited by erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA) (ic50 ∼ 4 μM). EHNA was shown to serve as a selective inhibitor of PDE-2 activity as assessed from studies using separated PDE1, PDE2, PDE3 and PDE4 species from hepatocytes as well as human PDE2 and PDE4 enzymes. EHNA completely ablated the ability of cyclic GMP to activate PDE2 activity, whilst having a much smaller inhibitory effect on the unstimulated PDE2 activity. EHNA exhibited normal Michaelian kinetics of inhibition for the cyclic GMP-stimulated PDE2 activity with Hill plots near unity. Apparent negative co-operative effects were seen in the absence of cyclic GMP with Hill coefficients of ∼0.3 for inhibition of PDE2 activity. Within 5 min of challenge of thymocytes with the lectin phytohaemagglutinin (PHA) there was a transient decrease (∼83%) in PDE-4 activity and in PDE2 activity (∼40%). Both anti-CD3 and anti-TCR antibodies also caused an initial reduction in the PDE4 activity which was followed by a sustained and profound increase in activity. In contrast to that observed with PHA, anti-TCR/CD3 antisera had little effect on PDE2 activity. It is suggested that, dependent upon the intracellular concentrations of cyclic GMP, thymocyte cyclic AMP metabolism can be expected to switch from being under the predominant control of PDE4 activity to that determined predominantly by PDE2 activity. These activities may be rapidly and differentially regulated following ligation of different cell surface receptors.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Harnett, Professor Margaret and Houslay, Professor Miles and Michie, Dr Alison
Authors: Michie, A. M., Lobban, M., Müller, T., Harnett, M. M., and Houslay, M. D.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cancer Sciences
College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
College of Medical Veterinary and Life Sciences > Institute of Neuroscience and Psychology
Journal Name:Cellular Signalling
ISSN:0898-6568
ISSN (Online):1873-3913

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