Cyclic Nucleotide-dependent Protein Kinases Target ARHGAP17 and ARHGEF6 Complexes in Platelets

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Title: Cyclic Nucleotide-dependent Protein Kinases Target ARHGAP17 and ARHGEF6 Complexes in Platelets
Authors: Nagy, Zoltan
Wynne, Kieran
Kriegsheim, Alexander von
Gambaryan, Stepan
Smolenski, Albert P.
Permanent link: http://hdl.handle.net/10197/7388
Date: 11-Dec-2015
Abstract: Endothelial cells release prostacyclin (PGI2) and nitric oxide (NO) to inhibit platelet functions. PGI2 and NO effects are mediated by cyclic nucleotides, cAMP- and cGMP-dependent protein kinases (PKA, PKG), and largely unknown PKA and PKG substrate proteins. The small G-protein Rac1 plays a key role in platelets and was suggested to be a target of cyclic nucleotide signaling. We confirm that PKA and PKG activation reduces Rac1-GTP levels. Screening for potential mediators of this effect resulted in the identification of the Rac1-specific GTPase-activating protein ARHGAP17 and the guanine nucleotide exchange factor ARHGEF6 as new PKA and PKG substrates in platelets. We mapped the PKA/PKG phosphorylation sites to serine 702 on ARHGAP17 using Phos-tag gels and to serine 684 on ARHGEF6. We show that ARHGAP17 binds to the actin-regulating CIP4 protein in platelets and that Ser-702 phosphorylation interferes with this interaction. Reduced CIP4 binding results in enhanced inhibition of cell migration by ARHGAP17. Furthermore, we show that ARHGEF6 is constitutively linked to GIT1, a GAP of Arf family small G proteins, and that ARHGEF6 phosphorylation enables binding of the 14-3-3 adaptor protein to the ARHGEF6/GIT1 complex. PKA and PKG induced rearrangement of ARHGAP17- and ARHGEF6-associated protein complexes might contribute to Rac1 regulation and platelet inhibition.
Funding Details: Irish Research Council
Science Foundation Ireland
Type of material: Journal Article
Publisher: American Society for Biochemistry and Molecular Biology
Copyright (published version): 2015 The American Society for Biochemistry and Molecular Biology, Inc.
Keywords: Rac (Rac GTPase);Cyclic AMP (cAMP);cyclic GMP (cGMP);Phosphorylation;Platelet
DOI: 10.1074/jbc.M115.678003
Language: en
Status of Item: Peer reviewed
Appears in Collections:Conway Institute Research Collection
SBI Research Collection
Medicine Research Collection

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