Synthesis of GPIbβ with novel transmembrane and cytoplasmic sequences in a Bernard–Soulier patient resulting in GPIb‐defective signaling in CHO cells

The molecular defect of a new Bernard–Soulier patient, originating from Morocco and presenting thrombocytopenia with large platelets and an absence of ristocetin‐induced platelet agglutination, has been identified and reproduced in transfected heterologous cells. Gene sequencing revealed insertion o...

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Bibliographic Details
Published in:Journal of thrombosis and haemostasis 2006-01, Vol.4 (1), p.217-228
Main Authors: STRASSEL, C., DAVID, T., ECKLY, A., BAAS, M‐J, MOOG, S., RAVANAT, C., TRZECIAK, M‐C, VINCIGUERRA, C., CAZENAVE, J‐P, GACHET, C., LANZA, F.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Bernard-Soulier Syndrome - blood
Bernard-Soulier Syndrome - complications
Bernard-Soulier Syndrome - genetics
Bernard–Soulier
Blood Platelets - pathology
Cell Membrane
Cell Shape
Child, Preschool
CHO Cells
Cricetinae
Cytoplasm
Female
Frameshift Mutation
GPIbβ
Humans
intracellular domain
Peptide Fragments
Platelet Glycoprotein GPIb-IX Complex - genetics
Signal Transduction - genetics
Thrombocytopenia - etiology
Transfection
von Willebrand Factor - metabolism
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Summary:The molecular defect of a new Bernard–Soulier patient, originating from Morocco and presenting thrombocytopenia with large platelets and an absence of ristocetin‐induced platelet agglutination, has been identified and reproduced in transfected heterologous cells. Gene sequencing revealed insertion of a guanine in the domain coding for the transmembrane region of the glycoprotein (GP) Ibβ subunit. This mutation causes a translational frame shift, which creates putative novel transmembrane and cytoplasmic 37 and 125 amino acids domains, respectively. A 34 kDa immunoreactive GPIbβ band, instead of the normal 26 kDa subunit, was detected by Western blotting in lysates from the patient's platelets and from transfected cells and in immunoprecipitates of metabolically labeled cells. The abnormal subunit did not associate with GPIbα and was mainly intracellular, although a significant fraction could reach the cell surface. Cells expressing the mutant GPIb–IX complex adhered to a von Willebrand factor matrix but were unable to change shape, unlike cells expressing the wild‐type receptor. These results strongly suggest a novel role of the GPIbβ subunit and its transmembrane‐intracellular region in GPIb‐VWF‐dependent signaling, in addition to a role in correct assembly and cell surface targeting of the GPIb–V–IX complex.
ISSN:1538-7933
1538-7836
1538-7836
DOI:10.1111/j.1538-7836.2005.01654.x