The human platelet antigen-1b (Pro33) variant of αIIbβ3 allosterically shifts the dynamic conformational equilibrium of this integrin toward the active state
| Autor: | Andreas R. P. Beck, Rüdiger E. Scharf, Volker R. Stoldt, Holger Gohlke, Joana Pereira, Giulia Pagani |
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| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
Gene isoform Conformational change 010304 chemical physics biology Chemistry HEK 293 cells Integrin Cell Biology 01 natural sciences Biochemistry 03 medical and health sciences Transmembrane domain 030104 developmental biology Förster resonance energy transfer Ectodomain 0103 physical sciences biology.protein Biophysics Binding site Molecular Biology |
| Zdroj: | Journal of Biological Chemistry. 293:4830-4844 |
| ISSN: | 0021-9258 |
| Popis: | Integrins are heterodimeric cell-adhesion receptors comprising α and β subunits that transmit signals allosterically in both directions across the membrane by binding to intra- and extracellular components. The human platelet antigen-1 (HPA-1) polymorphism in αIIbβ3 arises from a Leu → Pro exchange at residue 33 in the genu of the β3 subunit, resulting in Leu33 (HPA-1a) or Pro33 (HPA-1b) isoforms. Although clinical investigations have provided conflicting results, some studies have suggested that Pro33 platelets exhibit increased thrombogenicity. Under flow-dynamic conditions, the Pro33 variant displays prothrombotic properties, characterized by increased platelet adhesion, aggregate/thrombus formation, and outside-in signaling. However, the molecular events underlying this prothrombotic phenotype have remained elusive. As residue 33 is located >80 A away from extracellular binding sites or transmembrane domains, we hypothesized that the Leu → Pro exchange allosterically shifts the dynamic conformational equilibrium of αIIbβ3 toward an active state. Multiple microsecond-long, all-atom molecular dynamics simulations of the ectodomain of the Leu33 and Pro33 isoforms provided evidence that the Leu → Pro exchange weakens interdomain interactions at the genu and alters the structural dynamics of the integrin to a more unbent and splayed state. Using FRET analysis of fluorescent proteins fused with αIIbβ3 in transfected HEK293 cells, we found that the Pro33 variant in its resting state displays a lower energy transfer than the Leu33 isoform. This finding indicated a larger spatial separation of the cytoplasmic tails in the Pro33 variant. Together, our results indicate that the Leu → Pro exchange allosterically shifts the dynamic conformational equilibrium of αIIbβ3 to a structural state closer to the active one, promoting the fully active state and fostering the prothrombotic phenotype of Pro33 platelets. |
| Databáze: | OpenAIRE |
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