- 作者：Wei-Zhang Shen ; Qiu-Lan Ding ; Pei-Pei Jin ; Xue-Feng Wang ; Yu-Zhen Jiang ; Shu-Mei Li ; Hong-Li Wang
- 关键词：α ; IIb mutation ; α ; IIbβ ; 3 ; Glanzmann thrombasthenia ; Integrin
- 刊名：Blood Cells, Molecules, and Diseases
- 出版年：2009
- 出版时间：January-February 2009
- 年：2009
- 卷：42
- 期：1
- 页码：44-50
- 全文大小：1301 K
BackgroundGlanzmann thrombasthenia (GT) is an autosomal recessive bleeding disorder characterized by lack of platelet aggregation in response to most physiological agonists and caused by either a lack or dysfunction of the platelet integrin αIIbβ3 (glycoprotein IIb/IIIa).Patients
Mucocutaneous bleeding manifestations and platelet dysfunction consistent with GT were observed in a 20-year-old proband of a Chinese family.
Objectives
To determine the molecular basis of GT and characterize the mutation by in vitro expression studies.
Results
Analysis of the patient's platelets by fluorescence-activated cell sorting demonstrated the presence of trace amounts of β3, exposed on her platelet surface, but a complete absence of αIIbβ3. Sequence analysis revealed a novel C470A transversion in exon 4 of the αIIb gene predicting a Pro126His alteration in the blade 2 of the αIIb β propeller domain. The proband was homozygous for the mutation, the mother and the father were heterozygous, whereas 100 healthy subjects lacked this transversion. Chinese hamster ovary cells cotransfected with cDNAs of mutated αIIb and wild-type β3 failed to express αIIbβ3 on the cell surface as shown by FACS. Western blot analysis of the cell lysates showed no detectable mature αIIb. Immunoprecipitation with antibody against β3 demonstrated pro-αIIb in the cells expressing the mutant αIIbβ3, indicating pro-αIIbβ3 complex formation. Intracellular immunofluorescence studies demonstrated the pro-αIIbβ3 complex that co-localized with an ER marker, but showed minimal co-localization with a Golgi marker.
Conclusions
A novel Pro126His mutation in αIIb compromised transport of the pro-αIIbβ3 complex from the endoplasmic reticulum to the Golgi, leading to intracellular retention. The impaired αIIbβ3 transport is responsible for the thrombasthenia in this patient.