Thromb Haemost 2004; 92(06): 1377-1386
DOI: 10.1160/TH04-06-0380
Platelets and Blood Cells
Schattauer GmbH

A variant thrombasthenic phenotype associated with compound heterozygosity of integrin β3-subunit: (Met124Val)β3 alters the subunit dimerization rendering a decreased number of constitutive active αIIbβ3 receptors

Consuelo González-Manchón
1   Department of Physiopathology and Human Molecular Genetics, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain
,
Nora Butta
1   Department of Physiopathology and Human Molecular Genetics, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain
,
Susana Larrucea
1   Department of Physiopathology and Human Molecular Genetics, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain
,
Elena G. Arias-Salgado
1   Department of Physiopathology and Human Molecular Genetics, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain
,
Sonia Alonso
1   Department of Physiopathology and Human Molecular Genetics, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain
,
Angela López
1   Department of Physiopathology and Human Molecular Genetics, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain
,
Roberto Parrilla
1   Department of Physiopathology and Human Molecular Genetics, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain
› Author Affiliations

Financial support: This work has been supported in part by grants from the Direccion General de Investigacion (SAF 2000-0127, BMC2002-01053 and BMC2003-01409), Fondo de Investigaciones Sanitarias (FIS-PI021263). N. Butta is recipient of a tenure track grant Ramon y Cajal from the Spanish Ministry of Science. Susana Larrucea was supported by a postdoctoral fellowships from the Comunidad de Madrid (08.4/0015.1/2001) and Sonia Alonso by a predoctoral fellowship from the Gabierno Vasco (BF201-40).
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Publication History

Received 17 June 2004

Accepted after revision 20 September 2004

Publication Date:
04 December 2017 (online)

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Summary

We report the analysis of a variant case of thrombasthenic phenotype that is a compound heterozygote for two mutations located within the metal ion dependent adhesion site (MIDAS) of the β3 subunit.The patient inherited a maternal allele carrying the Met124Val substitution and a paternal allele that changes Asp119 to Tyr. Phenotyping of the human platelet antigen 1 (HPA-1) showed that the platelet αIIbβ3 complex in the patient was mostly accounted for by the Asp 119Tyr allele that does not bind to fibrinogen (Fg). The patient showed agonistinduced binding of platelets to Fg but neither binding to PAC-1 nor cell aggregation could be detected, most likely due to the minute expression (≤5%) of αIIb(124Val)β3 receptors. CHO cells expressing (124Val)β3 showed a diminished surface expression of αIIbβ3, enhanced adhesion to immobilized Fg, and spontaneous aggregation in the presence of soluble Fg, suggesting that (124Val)β3 may confer constitutive activity to the αIIb(124Val)β3 receptors. A distinct feature of these cells is the failure of DTT to enhance the binding to soluble Fg and the formation of cell aggregates. The substitution of (124Met)β3 by either a polar or a positively charged amino acid restored the surface exposure and function of the αIIbβ3 receptors whereas a negatively charged residue did not.