Rap1 binding to the talin 1 F0 domain makes a minimal contribution to murine platelet GPIIb-IIIa activation

Lagarrigue, F. and Gingras, Alexandre R. and Paul, D.S. and Valadez, A.J. and Cuevas, M.N. and Sun, H. and Lopez-Ramirez, M.A. and Goult, Benjamin T. and Shattil, S.J. and Bergmeier, W. and Ginsberg, M.H. (2018) Rap1 binding to the talin 1 F0 domain makes a minimal contribution to murine platelet GPIIb-IIIa activation. Blood Advances, 2 (18). pp. 2358-2368. ISSN 2473-9529. E-ISSN 2473-9529. (doi:https://doi.org/10.1182/bloodadvances.2018020487) (Full text available)

Abstract

Activation of platelet glycoprotein IIb-IIIa (GPIIb-IIIa; integrin aIIbb3) leads to high-affinity fibrinogen binding and platelet aggregation during hemostasis. Whereas GTP-bound Rap1 GTPase promotes talin 1 binding to the b3 cytoplasmic domain to activate platelet GPIIb-IIIa, the Rap1 effector that regulates talin association with b3 in platelets is unknown. Rap1 binding to the talin 1 F0 subdomain was proposed to forge the talin 1–Rap1 link in platelets. Here, we report a talin 1 point mutant (R35E) that significantly reduces Rap1 affinity without a significant effect on its structure or expression. Talin 1 head domain (THD) (R35E) was of similar potency to wild-type THD in activating aIIbb3 in Chinese hamster ovary cells. Coexpression with activated Rap1b increased activation, and coexpression with Rap1GAP1 reduced activation caused by transfection of wild-type THD or THD(R35E). Furthermore, platelets from Tln1R35E/R35E mice showed similar GPIIb-IIIa activation to those from wild- type littermates in response to multiple agonists. Tln1R35E/R35E platelets exhibited slightly reduced platelet aggregation in response to low doses of agonists; however, there was not a significant hemostatic defect, as judged by tail bleeding times. Thus, the Rap1–talin 1 F0 interaction has little effect on platelet GPIIb-IIIa activation and hemostasis and cannot account for the dramatic effects of loss of Rap1 activity on these platelet functions.

Item Type: Article
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculties > Sciences > School of Biosciences
Depositing User: Ben Goult
Date Deposited: 21 Sep 2018 17:27 UTC
Last Modified: 08 Oct 2018 10:43 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/69200 (The current URI for this page, for reference purposes)
Gingras, Alexandre R.: https://orcid.org/0000-0002-5373-0176
Goult, Benjamin T.: https://orcid.org/0000-0002-3438-2807
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