Essential role of zyxin in platelet biogenesis and glycoprotein Ib-IX surface expression

Zhongren Ding,Kesheng Dai,Kangxi Zhou,Yueyue Sun,Liuxia Yuan,Rong Yan,Suqin Zhang,Jincai Luo,Bin Cheng,Xinxin Ge,Changgeng Ruan,Mengnan Yang,Ningbo Pang,Honglei Ye

doi:10.1038/s41419-021-04246-x

Zhongren Ding, Kesheng Dai + Show 12 more

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https://doi.org/10.1038/s41419-021-04246-x

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Abstract

Platelets are generated from the cytoplasm of megakaryocytes (MKs) via actin cytoskeleton reorganization. Zyxin is a focal adhesion protein and wildly expressed in eukaryotes to regulate actin remodeling. Zyxin is upregulated during megakaryocytic differentiation; however, the role of zyxin in thrombopoiesis is unknown. Here we show that zyxin ablation results in profound macrothrombocytopenia. Platelet lifespan and thrombopoietin level were comparable between wild-type and zyxin-deficient mice, but MK maturation, demarcation membrane system formation, and proplatelet generation were obviously impaired in the absence of zyxin. Differential proteomic analysis of proteins associated with macrothrombocytopenia revealed that glycoprotein (GP) Ib-IX was significantly reduced in zyxin-deficient platelets. Moreover, GPIb-IX surface level was decreased in zyxin-deficient MKs. Knockdown of zyxin in a human megakaryocytic cell line resulted in GPIbα degradation by lysosomes leading to the reduction of GPIb-IX surface level. We further found that zyxin was colocalized with vasodilator-stimulated phosphoprotein (VASP), and loss of zyxin caused diffuse distribution of VASP and actin cytoskeleton disorganization in both platelets and MKs. Reconstitution of zyxin with VASP binding site in zyxin-deficient hematopoietic progenitor cell-derived MKs restored GPIb-IX surface expression and proplatelet generation. Taken together, our findings identify zyxin as a regulator of platelet biogenesis and GPIb-IX surface expression through VASP-mediated cytoskeleton reorganization, suggesting possible pathogenesis of macrothrombocytopenia.

Highlights

Platelets, the central regulator of thrombosis and hemostasis, are generated from the cytoplasm of megakaryocytes (MKs)
In order to investigate the role of zyxin in platelet biogenesis, we first performed a hematologic analysis in Zyx−/− mice
In this study, we report for the first time that zyxin is essential for platelet biogenesis and GPIb-IX surface expression

Summary

Introduction

The central regulator of thrombosis and hemostasis, are generated from the cytoplasm of megakaryocytes (MKs). MK progenitors migrate from BM osteoblastic niche to the vascular niche [3, 4], in which proplatelets are formed and released from the matured MKs into the bloodstream. Actin filaments localizing around the DMS network generate mechanical forces to initiate and mediate DMS formation [6]. Actin cytoskeleton reorganization guides the bending and bifurcating of the proplatelet shafts to increase the number of proplatelet ends [7]. Human mutations and genetargeted mice deficient in the components of the actin cytoskeleton, such as non-muscle myosin heavy chain IIA (NMMHC-IIA), α-actinin, filamin A, tropomyosin 4, diaphanousrelated formin 1 (DIAPH1), and tropomodulin 3, have shown thrombocytopenia due to abnormal platelet generation [8,9,10,11,12,13]. The molecular mechanisms underlying the complex process still remain elusive

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