Characterisation of the Ral GTPase inhibitor RBC8 in human and mouse platelets.

Autor: Walsh TG; From the School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol BS8 1TD, United Kingdom. Electronic address: tony.walsh@bristol.ac.uk., Wersäll A; From the School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol BS8 1TD, United Kingdom., Poole AW; From the School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol BS8 1TD, United Kingdom.
Jazyk: angličtina
Zdroj: Cellular signalling [Cell Signal] 2019 Jul; Vol. 59, pp. 34-40. Date of Electronic Publication: 2019 Mar 14.
DOI: 10.1016/j.cellsig.2019.03.015
Abstrakt: The Ral GTPases, RalA and RalB, have been implicated in numerous cellular processes, but are most widely known for having regulatory roles in exocytosis. Recently, we demonstrated that deletion of both Ral genes in a platelet-specific mouse gene knockout caused a substantial defect in surface exposure of P-selectin, with only a relatively weak defect in platelet dense granule secretion that did not alter platelet functional responses such as aggregation or thrombus formation. We sought to investigate the function of Rals in human platelets using the recently described Ral inhibitor, RBC8. Initial studies in human platelets confirmed that RBC8 could effectively inhibit Ral GTPase activation, with an IC 50 of 2.2 μM and 2.3 μM for RalA and RalB, respectively. Functional studies using RBC8 revealed significant, dose-dependent inhibition of platelet aggregation, secretion (α- and dense granule), integrin activation and thrombus formation, while α-granule release of platelet factor 4, Ca 2+ signalling or phosphatidylserine exposure were unaltered. Subsequent studies in RalAB-null mouse platelets pretreated with RBC8 showed dose-dependent decreases in integrin activation and dense granule secretion, with significant inhibition of platelet aggregation and P-selectin exposure at 10 μM RBC8. This study strongly suggests therefore that although RBC8 is useful as a Ral inhibitor in platelets, it is likely also to have off-target effects in the same concentration range as for Ral inhibition. So, whilst clearly useful as a Ral inhibitor, interpretation of data needs to take this into account when assessing roles for Rals using RBC8.
(Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)
Databáze: MEDLINE
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