Apolipoprotein A-IV polymorphisms Q360H and T347S attenuate its endogenous inhibition of thrombosis

Biochem Biophys Res Commun. 2024 Jun 18:712-713:149946. doi: 10.1016/j.bbrc.2024.149946. Epub 2024 Apr 16.

Abstract

Platelets are small anucleate cells that play a key role in thrombosis and hemostasis. Our group previously identified apolipoprotein A-IV (apoA-IV) as an endogenous inhibitor of thrombosis by competitive blockade of the αIIbβ3 integrin on platelets. ApoA-IV inhibition of platelets was dependent on the N-terminal D5/D13 residues, and enhanced with absence of the C-terminus, suggesting it sterically hinders its N-terminal platelet binding site. The C-terminus is also the site of common apoA-IV polymorphisms apoA-IV-1a (T347S) and apoA-IV-2 (Q360H). Interestingly, both are linked with an increased risk of cardiovascular disease, however, the underlying mechanism remains unclear. Here, we generated recombinant apoA-IV and found that the Q360H or T347S polymorphisms dampened its inhibition of platelet aggregation in human platelet-rich plasma and gel-filtered platelets, reduced its inhibition of platelet spreading, and its inhibition of P-selectin on activated platelets. Using an ex vivo thrombosis assay, we found that Q360H and T347S attenuated its inhibition of thrombosis at both high (1800s-1) and low (300s-1) shear rates. We then demonstrate a conserved monomer-dimer distribution among apoA-IV WT, Q360H, and T347S and use protein structure modelling software to show Q360H and T347S enhance C-terminal steric hindrance over the N-terminal platelet-binding site. These data provide critical insight into increased cardiovascular risk for individuals with Q360H or T347S polymorphisms.

Keywords: Apolipoprotein A-IV; Cardiovascular disease; Platelets; Polymorphisms; Thrombosis and hemostasis; αIIbβ3.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apolipoproteins A*
  • Apoprotein(a) / chemistry
  • Apoprotein(a) / genetics
  • Apoprotein(a) / metabolism
  • Blood Platelets* / drug effects
  • Blood Platelets* / metabolism
  • Humans
  • P-Selectin / genetics
  • P-Selectin / metabolism
  • Platelet Aggregation* / drug effects
  • Platelet Aggregation* / genetics
  • Polymorphism, Genetic
  • Thrombosis* / genetics
  • Thrombosis* / metabolism

Substances

  • apolipoprotein A-IV
  • Apoprotein(a)
  • P-Selectin
  • Apolipoproteins A