TY  - JOUR
AU  - Pagani, Guilia
AU  - Pereira, Joana P. V.
AU  - Stoldt, Volker R.
AU  - Beck, Andreas
AU  - Scharf, Rüdiger E.
AU  - Gohlke, Holger
TI  - The human platelet antigen-1b variant of $\alpha$$_{IIb}$β$_{3}$ allosterically shifts the dynamic conformational equilibrium of this integrin toward the active state
JO  - The journal of biological chemistry
VL  - 293
SN  - 0021-9258
CY  - Bethesda, Md.
PB  - Soc.
M1  - FZJ-2018-01518
SP  - 4830-4844
PY  - 2018
AB  - Integrins are heterodimeric cell-adhesion receptors comprising α and β subunits. 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 Leu-33 (HPA-1a) or Pro-33 (HPA-1b) isoforms. Although clinical investigations have provided conflicting results, some studies have suggested that Pro-33 platelets exhibit increased thrombogenicity. Under flow-dynamic conditions, the Pro-33 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 Å 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 Leu-33 and Pro-33 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 Pro-33 variant in its resting state displays a lower energy transfer than the Leu-33 isoform. This finding indicated a larger spatial separation of the cytoplasmic tails in the Pro-33 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 Pro-33 platelets.
LB  - PUB:(DE-HGF)16
C6  - pmid:29462793
UR  - <Go to ISI:>//WOS:000428848300023
DO  - DOI:10.1074/jbc.RA118.002149
UR  - https://juser.fz-juelich.de/record/844002
ER  -