Premium
A humanized monoclonal antibody that inhibits platelet‐surface ER p72 reveals a role for ER p72 in thrombosis
Author(s) -
Holbrook L.M.,
Sandhar G. K.,
Sasikumar P.,
Schenk M. P.,
Stainer A. R.,
Sahli K. A.,
Flora G. D.,
Bicknell A. B.,
Gibbins J. M.
Publication year - 2018
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.13878
Subject(s) - monoclonal antibody , endoplasmic reticulum , platelet , protein disulfide isomerase , platelet activation , enzyme , intracellular , chemistry , thiol , biochemistry , microbiology and biotechnology , antibody , biology , immunology
Essentials ERp72 is a thiol isomerase enzyme. ERp72 levels increase at the platelet surface during platelet activation. We generated a humanized monoclonal antibody which blocks ERp72 enzyme activity (anti‐ERp72). Anti‐ERp72 inhibits platelet functional responses and thrombosis.Summary Background Within the endoplasmic reticulum, thiol isomerase enzymes modulate the formation and rearrangement of disulfide bonds in newly folded proteins entering the secretory pathway to ensure correct protein folding. In addition to their intracellular importance, thiol isomerases have been recently identified to be present on the surface of a number of cell types where they are important for cell function. Several thiol isomerases are known to be present on the resting platelet surface, including PDI , ER p5 and ER p57, and levels are increased following platelet activation. Inhibition of the catalytic activity of these enzymes results in diminished platelet function and thrombosis. Aim We previously determined that ER p72 is present at the resting platelet surface and levels increase upon platelet activation; however, its functional role on the cell surface was unclear. We aimed to investigate the role of ER p72 in platelet function and its role in thrombosis. Methods Using Hu CAL technology, fully humanized Fc‐null anti‐ ER p72 antibodies were generated. Eleven antibodies were screened for their ability to inhibit ER p72 activity and the most potent inhibitory antibody (anti‐ ER p72) selected for further testing in platelet functional assays. Results and conclusions Anti‐ ER p72 inhibited platelet aggregation, granule secretion, calcium mobilisation and integrin activation, revealing an important role for extracellular ER p72 in the regulation of platelet activation. Consistent with this, infusion of anti‐ ER p72 into mice protected against thrombosis.