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Haematologica 2020 Volume 105(11):2608-2618
Platelet Biology & its Disorders
Migfilin supports hemostasis and thrombosis through regulating platelet aIIbβ3 outside-in signaling
Yangfan Zhou,1,2 Mengjiao Hu,1,2 Xiaoyan Chen,1,2 Shuai Wang,1,2 Jingke Li,1,2 Lina Sa,1,2 Li Li,1,2 Jiaqi Huang,3 Hongqiang Cheng3 and Hu Hu1,2,4
1Department of Pathology and Pathophysiology and Bone Marrow Transplantation Center of the First Affiliated Hospital, Zhejiang University School of Medicine; 2Institute of Hematology, Zhejiang University & Zhejiang Engineering Laboratory for Stem Cell and Immunotherapy; 3Department of Pathology and Pathophysiology, and Department of Cardiology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine and 4Key Laboratory of Disease Proteomics of Zhejiang Province, Hangzhou, China
ABSTRACT
Elucidating the regulation mechanism of integrin aIIbβ3 is key to under- standing platelet biology and thrombotic diseases. Previous in vitro studies have implicated a role of migfilin in the support of platelet aIIbβ3 activation, however, contribution of migfilin to thrombosis and hemostasis in vivo and a detailed mechanism of migfilin in platelets are not known. In this study, through migfilin knock-out (migfilin-/-) mice, we report that migfilin is a pivotal positive regulator of hemostasis and thrombosis. Migfilin-/- mice show a nearly doubled tail-bleeding time and a prolonged occlusion time in FeCl3-induced mesenteric arteriolar thrombosis. Migfilin deficiency impedes platelet thrombi formation on a collagen surface and impairs platelet aggregation and dense-granule secretion. Supported by characteristic functional readings and the phosphorylation status of distinc- tive signaling molecules in the bidirectional signaling processes of aIIbβ3, the functional defects of migfilin-/- platelets appear to be mechanistically asso- ciated with a compromised outside-in signaling, rather than inside-out signaling. A synthesized cell-permeable migfilin peptide harboring filamin A binding sequence rescued the defective function and phosphorylation of sig- naling molecules of migfilin-/- platelets. Finally, migfilin does not influence the binding of filamin A and β3 subunit of aIIbβ3 in resting platelets, but hampers the re-association of filamin A and β3 during the conduct of out- side-in signaling, suggesting that migfilin functions through regulating the interaction dynamics of aIIbβ3 and filamin A in platelets. Our study enhances the current understanding of platelet integrin aIIbβ3-mediated outside-in signaling and proves that migfilin is an important regulator for platelet activation, hemostasis and thrombosis.
Introduction
Platelets are essential for thrombosis and hemostasis. At the sites of vascular injury, platelets instantly activate, adhere to the exposed subendothelial matrix and form a hemostatic or thrombotic plug. Idiosyncratically expressed by platelets, integrin aIIbβ3isthecentraladhesionmoleculethatgovernstheprocessofthrom- bus formation. aIIbβ3 characteristically transmits signals bidirectionally across the plasma membrane, processes termed inside-out and outside-in signaling, respec- tively.1 Inside-out signaling conveys the activation information from stimuli and culminates in the high affinity binding of aIIbβ3 to its ligands, which forms bridges to support platelet-vessel wall adhesion and platelet homotypic aggregation. Outside-in signaling, which is initiated by ligand binding and aIIbβ3 clustering, is essential for platelet spreading, clot retraction and thrombus consolidation.2
Platelet aIIbβ3 signaling is regulated by the binding of several molecules to the cytoplasmic domain of integrin β-subunits.3 The cytoplasmic integrin-binding pro- tein talin has been known as the central regulator for aIIbβ3.4 There are also other
Correspondence:
HU HU/HONGQIANG CHENG
huhu@zju.edu.cn/hqcheng11@zju.edu.cn
Received: July 15, 2019.
Accepted: December 18, 2019. Pre-published: December 26, 2019.
doi:10.3324/haematol.2019.232488 ©2020 Ferrata Storti Foundation
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