Scanning peptide array analyses identify overlapping binding sites for the signalling scaffold proteins, beta-arrestin and RACK1, in cAMP-specific phosphodiesterase PDE4D5
Authors: George S Baillie
Martin J Lynch
Angela McCahill
Lisa High Mitchell
Christian Hundsrucker
Pawel Herzyk
Xiang Li
Ahmed Mohamed
Enno Klussmann
Miles D Houslay
David R Adams
Graeme B Bolger
Journal: Biochemical Journal (2006)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: cAMP-specific phosphodiesterase; PDE4D5; RACK1; beta-arrestin; scaffold proteins
Affiliations: Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35294-3300, USA., Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K., Sir Henry Wellcome Functional Genomics Facility, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K., Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35294-3300, U.S.A., Forschungsinstitut für Molekulare Pharmakologie, Campus Berlin-Buch, Robert-Rössle-Str. 10, 13125 Berlin, Germany, Department of Chemistry, Heriot-Watt University, Edinburgh EH14 4AS, Scotland, U.K.

Abstract:  The cAMP-specific phosphodiesterase PDE4D5 can interact with the signalling scaffold proteins RACK (receptors for activated C-kinase) 1 and beta-arrestin. Two-hybrid and co-immunoprecipitation analyses showed that RACK1 and beta-arrestin interact with PDE4D5 in a mutually exclusive manner. Overlay studies with PDE4D5 scanning peptide array libraries showed that RACK1 and beta-arrestin interact at overlapping sites within the unique N-terminal region of PDE4D5 and at distinct sites within the conserved PDE4 catalytic domain. Screening scanning alanine substitution peptide arrays, coupled with mutagenesis and truncation studies, allowed definition of RACK1 and beta-arrestin interaction sites. Modelled on the PDE4D catalytic domain, these form distinct well-defined surface-exposed patches on helices-15-16, for RACK1, and helix-17 for beta-arrestin. siRNA (small interfering RNA)-mediated knockdown of RACK1 in HEK-293 (human embryonic kidney) B2 cells increased beta-arrestin-scaffolded PDE4D5 approx. 5-fold, increased PDE4D5 recruited to the beta2AR (beta2-adrenergic receptor) upon isoproterenol challenge approx. 4-fold and severely attenuated (approx. 4-5 fold) both isoproterenol-stimulated PKA (protein kinase A) phosphorylation of the beta2AR and activation of ERK (extracellular-signal-regulated kinase). The ability of a catalytically inactive form of PDE4D5 to exert a dominant negative effect in amplifying isoproterenol-stimulated ERK activation was ablated by a mutation that blocked the interaction of PDE4D5 with beta-arrestin. In the present study, we show that the signalling scaffold proteins RACK1 and beta-arrestin compete to sequester distinct 'pools' of PDE4D5. In this fashion, alterations in the level of RACK1 expression may act to modulate signal transduction mediated by the beta2AR. 

Retracted: No

PubPeer comments:
 The helicase inhibition (shown [here] for flaviviruses makes the most sense) - its is [highly conserved in viruses] . , 
 Dear authors, You report in this paper (unfortunately without showing the corresponding results) that  no toxicity of ivermectin was observed at any of the timepoints tested, in either the sample wells or in parallel tested drug alone samples . This is surprising given the following cytotoxicity results reported in the NIH OpenData Portal ( https: opendata.ncats.nih.gov covid19 sample summary NCGC00094047 ): ![file] The ability of IVM to reverse the viral induced cytopathic effect does not seem consistent either: ![file] Could you please comment on these results? With many thanks. ,