A β3 Asp217→Val substitution in a patient with variant Glanzmann Thrombasthenia severely affects integrin αIIBβ3 functions

A dysfunctional Glanzmann Thrombasthenia (variant) is a rare bleeding disorder due to qualitative abnormalities of platelets alpha IIB beta 3 heterodimers. Dynamically conformational change of alpha IIB beta 3 is a complex mechanism that is not fully understood. For these reasons, genotyping and functional analysis of variant Glanzmann Thrombasthenia is important to elucidate the molecular basis of receptor functions. In this report, we have analyzed the molecular effects of an A>T substitution leading to an amino acid change, D217>V, in the beta 3 integrin gene identified in patients with variant Glanzmann Thrombasthenia. As the D217 residue is highly conserved among all seven beta integrin subunits and among beta 3 integrins of different species, we tested the effect on the phenotype of the D217V mutation by cotransfecting the beta 3 mutant (V217) or wild-type beta 3 (D217) construct with the wild-type alpha IIb into eukaryotic Chinese hamster ovary cells. Levels of mutant alpha IIB beta 3 heterodimers on Chinese hamster ovary cell surface were lightly reduced as compared with the wild type. Functional investigation of alpha IIB beta 3 V217 on Chinese hamster ovary cell surface was carried out, as fibrinogen binding, adhesion and aggregation tests showed a substantial reduction in respect to the control sample. Our results confirm ex-vivo data and suggest that the D217 amino acid is required for alpha IIB beta 3 receptor interactions with fibrinogen. Blood Coagul Fibrinolysis 19:657-662 (C) 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins.