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Tischer A, Machha VR, Moon-Tasson L, Auton M. Platelet-type von Willebrand disease: Local disorder of the platelet GPIbα β-switch drives high-affinity binding to von Willebrand factor. J Thromb Haemost 2019; 17:2022-2034. [PMID: 31448872 DOI: 10.1111/jth.14597] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 07/26/2019] [Indexed: 11/29/2022]
Abstract
BACKGROUND Mutations in the β-switch of GPIbα cause gain-of-function in the platelet-type von Willebrand disease. Structures of free and A1-bound GPIbα suggest that the β-switch undergoes a conformational change from a coil to a β-hairpin. OBJECTIVES Platelet-type von Willebrand disease (VWD) mutations have been proposed to stabilize the β-switch by shifting the equilibrium in favor of the β-hairpin, a hypothesis predicated on the assumption that the complex crystal structure between A1 and GPIbα is the high-affinity state. METHODS Hydrogen-deuterium exchange mass spectrometry is employed to test this hypothesis using G233V, M239V, G233V/M239V, W230L, and D235Y disease variants of GPIbα. If true, the expectation is a decrease in hydrogen-deuterium exchange within the β-switch as a result of newly formed hydrogen bonds between the β-strands of the β-hairpin. RESULTS Hydrogen-exchange is enhanced, indicating that the β-switch favors the disordered loop conformation. Hydrogen-exchange is corroborated by differential scanning calorimetry, which confirms that these mutations destabilize GPIbα by allowing the β-switch to dissociate from the leucine-rich-repeat (LRR) domain. The stability of GPIbα and its A1 binding affinity, determined by surface plasmon resonance, are correlated to the extent of hydrogen exchange in the β-switch. CONCLUSION These studies demonstrate that GPIbα with a disordered loop is binding-competent and support a mechanism in which local disorder in the β-switch exposes the LRR-domain of GPIbα enabling high-affinity interactions with the A1 domain.
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Affiliation(s)
- Alexander Tischer
- Division of Hematology, Departments of Internal Medicine and Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA
| | - Venkata R Machha
- Division of Hematology, Departments of Internal Medicine and Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA
| | - Laurie Moon-Tasson
- Division of Hematology, Departments of Internal Medicine and Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA
| | - Matthew Auton
- Division of Hematology, Departments of Internal Medicine and Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA
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Chang WA, Sheu CC, Liu KT, Shen JH, Yen MC, Kuo PL. Identification of mutations in SLC4A1, GP1BA and HFE in a family with venous thrombosis of unknown cause by next-generation sequencing. Exp Ther Med 2018; 16:4172-4180. [PMID: 30344693 DOI: 10.3892/etm.2018.6693] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 05/17/2018] [Indexed: 12/28/2022] Open
Abstract
Various risk factors, including high age, female gender, obesity and certain genetic defects have been linked to venous thrombosis. A Taiwanese family with venous thrombosis of unknown cause were enrolled in the present study. In this pedigree, two women without any specific underlying diseases suffered from venous thrombotic events at the same age. No specific risk factors or coagulation abnormalities were identified. The main proband's younger brother also had intestinal arterial thrombosis at 54 years of age. Therefore, it was hypothesized that familial genetic defects may be the cause of venous thrombosis within this family. Blood samples collected from certain members of this pedigree were subjected to whole-exome sequencing, and three genetic variants were identified, including a missense variant of solute carrier family 4 member 1 (SLC4A1) (c.388G>A), a deletion on glycoprotein Ib platelet α subunit (GP1BA) (c.1322_1344del23) and an insertion in the splice site of homeostatic iron regulator (HFE). To date, none of these three genetic variants have been reported to be associated with venous thrombosis, to the best of our knowledge. The present study suggests that these genetic variants of SLC4A1, GP1BA and HFE may be associated with venous thrombosis in an Asian pedigree.
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Affiliation(s)
- Wei-An Chang
- Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C.,Division of Pulmonary and Critical Care Medicine, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan, R.O.C
| | - Chau-Chyun Sheu
- Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C.,Division of Pulmonary and Critical Care Medicine, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan, R.O.C.,School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C
| | - Kuan-Ting Liu
- Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C.,School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C.,Department of Emergency Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C
| | - Jheng-Heng Shen
- Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C.,Department of Emergency Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C
| | - Meng-Chi Yen
- Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C.,Department of Emergency Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C
| | - Po-Lin Kuo
- Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C
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Affiliation(s)
- Maha Othman
- a Department of Biomedical and Molecular Sciences, Faculty of Medicine , Queen's University , Kingston , Canada.,b School of Baccalaureate Nursing , St. Lawrence College , Kingston , Canada
| | - Jonas Emsley
- c School of Pharmacy, Centre for Biomolecular Sciences , University of Nottingham , Nottingham , UK
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