The integrin PSI domain has an endogenous thiol isomerase function and is a novel target for antiplatelet therapy

Guangheng Zhu, Qing Zhang, Emily C. Reddy, Naadiya Carrim, Yunfeng Chen, Xiaohong Ruby Xu, Miao Xu, Yiming Wang, Yan Hou, Li Ma, Yan Li, Min Rui, Tania N. Petruzziello-Pellegrini, Christopher Lavalle, Tyler W. Stratton, Xi Lei, Reheman Adili, Pingguo Chen, Cheng Zhu, John A. WilkinsRichard O. Hynes, John Freedman, Heyu Ni

Research output: Contribution to journalArticlepeer-review


Integrins are a large family of heterodimeric transmembrane receptors differentially expressed on almost all metazoan cells. Integrin b subunits contain a highly conserved plexin-semaphorin-integrin (PSI) domain. The CXXC motif, the active site of the protein-disulfide-isomerase (PDI) family, is expressed twice in this domain of all integrins across species. However, the role of the PSI domain in integrins and whether it contains thiol-isomerase activity have not been explored. Here, recombinant PSI domains of murine b3, and human b1 and b2 integrins were generated and their PDI-like activity was demonstrated by refolding of reduced/denatured RNase. We identified that both CXXC motifs of b3 integrin PSI domain are required to maintain its optimal PDI-like activity. Cysteine substitutions (C13A and C26A) of the CXXC motifs also significantly decreased the PDI-like activity of full-length human recombinant b3 subunit. We further developed mouse anti-mouse b3 PSI domain monoclonal antibodies (mAbs) that cross-react with human and other species. These mAbs inhibited aIIbb3 PDI-like activity and its fibrinogen binding. Using single-molecular Biomembrane-Force-Probe assays, we demonstrated that inhibition of aIIbb3 endogenous PDI-like activity reduced aIIbb3-fibrinogen interaction, and these anti-PSI mAbs inhibited fibrinogen binding via different levels of both PDI-like activity-dependent and -independent mechanisms. Importantly, these mAbs inhibited murine/ human platelet aggregation in vitro and ex vivo, and murine thrombus formation in vivo, without significantly affecting bleeding time or platelet count. Thus, the PSI domain is a potential regulator of integrin activation and a novel target for antithrombotic therapies. These findings may have broad implications for all integrin functions, and cell-cell and cell-matrix interactions.

Original languageEnglish (US)
Pages (from-to)1840-1854
Number of pages15
Issue number13
StatePublished - Mar 30 2017
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology


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