Targeting of type I protein kinase A to lipid rafts is required for platelet inhibition by the 3',5'-cyclic adenosine monophosphate-signaling pathway.

Abstract

BACKGROUND:

Platelet adhesion to von Willebrand factor (VWF) is modulated by 3',5'-cyclic adenosine monophosphate (cAMP) signaling through protein kinase A (PKA)-mediated phosphorylation of glycoprotein (GP)Ibβ. A-kinase anchoring proteins (AKAPs) are proposed to control the localization and substrate specificity of individual PKA isoforms. However, the role of PKA isoforms in regulating the phosphorylation of GPIbβ and platelet response to VWF is unknown.

OBJECTIVES:

We wished to determine the role of PKA isoforms in the phosphorylation of GPIbβ and platelet activation by VWF as a model for exploring the selective partitioning of cAMP signaling in platelets.

RESULTS:

The two isoforms of PKA in platelets, type I (PKA-I) and type II (PKA-II), were differentially localized, with a small pool of PKA-I found in lipid rafts. Using a combination of Far Western blotting, immunoprecipitation, proximity ligation assay and cAMP pull-down we identified moesin as an AKAP that potentially localizes PKA-I to rafts. Introduction of cell-permeable anchoring disruptor peptide, RI anchoring disruptor (RIAD-Arg11 ), to block PKA-I/AKAP interactions, uncoupled PKA-RI from moesin, displaced PKA-RI from rafts and reduced kinase activity in rafts. Examination of GPIbβ demonstrated that it was phosphorylated in response to low concentrations of PGI2 in a PKA-dependent manner and occurred primarily in lipid raft fractions. RIAD-Arg11 caused a significant reduction in raft-localized phosphoGPIbβ and diminished the ability of PGI2 to regulate VWF-mediated aggregation and thrombus formation in vitro.

CONCLUSION:

We propose that PKA-I-specific AKAPs in platelets, including moesin, organize a selective localization of PKA-I required for phosphorylation of GPIbβ and contribute to inhibition of platelet VWF interactions.

• Authors: Z Raslan, S Magwenzi, A Aburima, K Taskén, K M Naseem
• Journal: Journal of thrombosis and haemostasis : JTH (J Thromb Haemost) Vol. 13 Issue 9 Pg. 1721-34 (Sep 2015) ISSN: 1538-7836 [Electronic] England
• PMID: 26176741 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2015 International Society on Thrombosis and Haemostasis.

Chemical References

• A Kinase Anchor Proteins
• Microfilament Proteins
• Peptide Fragments
• Platelet Glycoprotein GPIb-IX Complex
• Platelet Membrane Glycoproteins
• Protein Isoforms
• Protein Kinase Inhibitors
• von Willebrand Factor
• von Willebrand factor receptor
• moesin
• Epoprostenol
• Cyclic AMP
• Cyclic AMP-Dependent Protein Kinase Type I

Topics

• A Kinase Anchor Proteins (blood, physiology)
• Amino Acid Sequence
• Cyclic AMP (physiology)
• Cyclic AMP-Dependent Protein Kinase Type I (antagonists & inhibitors, blood)
• Epoprostenol (pharmacology)
• Humans
• Membrane Microdomains (metabolism)
• Microfilament Proteins (metabolism)
• Molecular Sequence Data
• Peptide Fragments (chemical synthesis, pharmacology)
• Phosphorylation
• Platelet Adhesiveness (physiology)
• Platelet Glycoprotein GPIb-IX Complex (metabolism)
• Platelet Membrane Glycoproteins (metabolism)
• Protein Binding
• Protein Isoforms (blood)
• Protein Kinase Inhibitors (pharmacology)
• Protein Processing, Post-Translational
• Second Messenger Systems (physiology)
• von Willebrand Factor (metabolism)