Studies on PDE4 cyclic AMP-specific phosphodiesterases

O'Connell, Jonathan Curtis (1996) Studies on PDE4 cyclic AMP-specific phosphodiesterases. PhD thesis, University of Glasgow.

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The type 4 family of phosphodiesterases (PDEs) are part of family of enzymes that provide the sole means of hydrolysing the ubiquitous second messenger, adenosine-3',5'-cyclic monophosphate. The PDE4 family is complex, consisting of four genes, each of which is alternatively spliced. Understanding the functional significance of the multiple species is crucial so as to enable the development of novel drugs to modulate their activities for the treatment of many disorders, including depression, asthma and arthritis. In this study, the regulation of PDE4B splice variants by insulin in intact rat epididymal adipocytes was investigated and the expression of PDE4B species in a number of cell lines was detected using antisera designed to recognise the C-terminal region of PDE4B species. Described herein is the first demonstration of the interaction of PDE4 isoforms with Src homology-3 (SH3) domains. The PDE4A species, rpde6 (RNPDE4A5) and the PDE4D species PDE4D4, when expressed either transiently in COS cells or endogenously in brain, were shown to possess the ability to bind to SH3 domains of certain Src family tyrosyl kinases, that were expressed as glutathione-S-transferase (GST) fusion proteins. Neither PDE isoforms interacted with GST itself PDE4D4 and rpde6 displayed little or no binding to the SH3 domains of the adapter proteins Grb2 and Crk, thus displaying specificity for the SH3 domains with which they interacted. Interaction was determined by the N-terminal splice region of rpde6 since the PDE4A splice variant rpde39, which differs from rpde6 at the N-terminus failed to interact with SH3 domains at all. This occurred both when rpde39 was either transiently expressed in COS cells or endogenously expressed in testes. The interaction of PDE4D4 with SH3 domains appeared to be determined by its N-terminal splice region since the other PDE4D splice variants, PDE4D3 and PDE4D5, which differ from PDE4D4 only in their extreme N-terminally spliced regions, did not interact with SH3 domains rpde6 but not PDE4D4 was shown to interact with the SH3 domains of Crk, Lck and Csk, as well as the cytoskeletal protein fodrin, leading to a perturbation of the catalytic activity of rpde6. In contrast, association with the SH3 domains of Src family tyrosyl kinases, Src, Fyn and Lyn did not effect the catalytic activity, Km or sensitivity to the PDE4 specific inhibitor rolipram of rpde6. The basis and possible functional significance of such interactions is described.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Molecular biology.
Colleges/Schools: College of Medical Veterinary and Life Sciences
Supervisor's Name: Houslay, Professor Miles
Date of Award: 1996
Depositing User: Enlighten Team
Unique ID: glathesis:1996-71844
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 17 May 2019 09:31
Last Modified: 30 Aug 2022 08:29
Thesis DOI: 10.5525/gla.thesis.71844

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