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Analysis of inter‐subunit contacts reveals the structural malleability of extracellular domains in platelet glycoprotein Ib‐IX complex
Author(s) -
Zhou L.,
Yang W.,
Li R.
Publication year - 2014
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/jth.12437
Subject(s) - extracellular , platelet membrane glycoprotein , glycoprotein , protein subunit , chinese hamster ovary cell , platelet glycoprotein gpib ix complex , chemistry , microbiology and biotechnology , biology , receptor , biochemistry , gene
Summary Background The glycoprotein ( GP )Ib‐ IX complex is critical to hemostasis and thrombosis. Its proper assembly is closely correlated with its surface expression level and requires cooperative interactions among extracellular and transmembrane domains of Ibα, Ibβ and IX subunits. Two interfaces have been previously identified between the extracellular domains of Ibβ and IX . Objective To understand how extracellular domains interact in GPI b‐ IX . Methods The Ibβ extracellular domain (Ibβ E ) or the IX counterpart ( IX E ) in GPI b‐ IX was replaced with a well‐folded Ibβ E / IX E chimera called Ibβ Eabc , and the effect of domain replacement on assembly and expression of the receptor complex in transiently transfected Chinese hamster ovary cells was analyzed. Results Replacing IX E with Ibβ Eabc in GPI b‐ IX retained interface 1 but not interface 2 between the extracellular domains. While this domain replacement preserved complex integrity, the expression levels of Ibβ and Ibα were significantly reduced. Additional domain replacement with Ibβ Eabc or Ibβ E in GPI b‐ IX produced the complex at disparate expression levels that cannot be simply explained by two separate interfaces. In particular, when Ibβ E in GPI b‐ IX was replaced by Ibβ Eabc , Ibα and IX were expressed at approximately 70% of the wild‐type level. Their levels were not reduced when IX E was changed further to Ibβ E . Conclusions Our results demonstrate the importance of the association between Ibβ and IX extracellular domains for complex assembly and efficient expression, and provide evidence for the structural malleability of these domains that may accommodate and propagate conformational changes therein.