Expression and subcellular localization of WAVE isoforms in the megakaryocyte/platelet lineage

Authors

  • H. KASHIWAGI,

    1. Department of Hematology and Oncology, Osaka University Graduate School of Medicine, Osaka, Japan; Department of Blood Transfusion, Osaka University Hospital, Osaka, Japan
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  • M. SHIRAGA,

    1. Department of Hematology and Oncology, Osaka University Graduate School of Medicine, Osaka, Japan; Department of Blood Transfusion, Osaka University Hospital, Osaka, Japan
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  • H. KATO,

    1. Department of Hematology and Oncology, Osaka University Graduate School of Medicine, Osaka, Japan; Department of Blood Transfusion, Osaka University Hospital, Osaka, Japan
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  • S. HONDA,

    1. National Cardiovascular Center Research Institute, Osaka, Japan
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  • M. SAKO,

    1. Osaka City General Hospital, Osaka, Japan
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  • Y. KURATA,

    1. Department of Hematology and Oncology, Osaka University Graduate School of Medicine, Osaka, Japan; Department of Blood Transfusion, Osaka University Hospital, Osaka, Japan
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  • Y. KANAKURA,

    1. Department of Hematology and Oncology, Osaka University Graduate School of Medicine, Osaka, Japan; Department of Blood Transfusion, Osaka University Hospital, Osaka, Japan
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  • Y. TOMIYAMA

    1. Department of Hematology and Oncology, Osaka University Graduate School of Medicine, Osaka, Japan; Department of Blood Transfusion, Osaka University Hospital, Osaka, Japan
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  • This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, and Culture in Japan, Yamanouchi Foundation for Research and Metabolic Disorders (Tsukuba, Japan), and Mitsubishi Pharma Research Foundation (Osaka, Japan).

H. Kashiwagi, Department of Hematology and Oncology, Osaka University Graduate School of Medicine, 2-2, Yamada-oka, Suita, Osaka 565-0871, Japan.
Tel.: +81 6 6879 3871; fax: +81 6 6879 3879; e-mail: kashi@hp-blood.med.osaka-u.ac.jp

Abstract

Summary.  WAVE isoforms, which consist of WAVE-1, WAVE-2 and WAVE-3, are members of the Wiskott–Aldrich syndrome protein (WASP) family. They are implicated in the regulation of actin-cytoskeletal reorganization downsteam of the small GTPase, Rac. Since platelet attachment to extracellular matrices leads to filopodial and lamellipodial extension, we examined the expression and subcellular localization of WAVEs in platelets. Employing primary megakaryocytic cells derived from cord blood as well as megakaryocytic cell lines, we also examined their expression during megakaryocytic differentiation. Immunoblotting and immunohistochemical analysis revealed that platelets expressed WAVE-1 and WAVE-2, whereas WAVE-3 expression was hardly to be detected. WAVE-1 expression was associated with megakaryocytic differentiation, whereas WAVE-2 and WAVE-3 expression was not changed by the differentiation. In adhered platelets both WAVE-1 and WAVE-2 were localized at the edge of the lamellipodia and at the tips of filopodia. In WASP-deficient platelets we found normal lamellipodial formation and localization of WAVE-1 and WAVE-2 at the edges of lamellipodia. Furthermore, we demonstrated that WAVE-1 and WAVE-2 moved from a detergent-soluble cytosolic fraction to insoluble cytoskeleton fraction after platelet aggregation. These results suggest that WAVE-1 and WAVE-2 regulate actin reorganization during platelet spreading and aggregate formation.

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