OC 68.4 - Transmembrane TMX1 counterbalances the effect of ERp46 to inhibit platelet activation

Tuesday, June 25, 2024

15:30 – 15:45 ICT

Room: 211 A-D

Presenting Author(s)

Zhenzhen Zhao, MD

Postdoc
Soochow Universtiy
SuZhou, Jiangsu, China (People's Republic)

Co-Author(s)

yc

yixin cheng

MD
National Clinical Research Center for Hematologic Diseases,Soochow University
Suzhou, Jiangsu, China (People's Republic)
mp

meinan peng

MD
Soochow University
Suzhou, Jiangsu, China (People's Republic)
yz

yuxin zhang

MM
National Clinical Research Center for Hematologic Diseases, Cyrus Tang Medical Institute，Soochow University
Suzhou, Jiangsu, China (People's Republic)
SL

Shuo Liu

MD
Soochow University
Suzhou, Jiangsu, China (People's Republic)
YS

Yaowei Sun

Graduate student
Soochow Universtiy
Suzhou, Jiangsu, China (People's Republic)
Yh

Yue han

Professor
National Clinical Research Center for Hematologic Diseases, Jiangsu Institute of Hematology, Institute of Blood and Marrow Transplantation, Collaborative Innovation Center of Hematology, First Affiliated Hospital of Soochow University
Suzhou, Jiangsu, China (People's Republic)
DW

Depei Wu

Professor
The First Affiliated Hospital of Soochow University
Suzhou, Jiangsu, China (People's Republic)
Aizhen Yang, PhD

Associate researcher
The Cyrus Tang Hematology Center, Soochow University
SuZhou, Jiangsu, China (People's Republic)

Background: Thioredoxin domain containing proteins (TXNDCs) are a group of thiol oxidoreductases that possess CXXC motif. Previous studies have shown some TXNDCs such as TXNDC5 (also known as ERp46) positively regulate platelet function by reducing integrin αIIbβ3 disulfide bonds. We previously found that the transmembrane TXNDC1 (TMX1) is a negative regulator of platelet activation and integrin αIIbβ3 function. However, whether and how the positive and negative PDIs interact with each other, and their interaction is involved in platelet activation remains unknown.

Aims: This study aimed to study whether and how TMX1 balances the effect of positive TXNDCs to regulate platelet function.

Methods: We used TMX1-deficient platelet, anti-TMX1 antibody, wild-type and inactive TMX1 protein (TMX1-OO) and studied the antagonistic effect of TMX1 on ERp46 in platelet aggregation, clot retraction, and integrin αIIbβ3 signaling. The underlying mechanisms were further determined using thiol labeling, reductase activity as well as other assays.

Results: Anti-TMX1 antibody and TMX1-OO reversed the decreased aggregation of ERp46-deficient platelets in response to different stimuli. Anti-TMX1 antibody reversed the attenuated “inside-out” and “outside-in” signaling of αIIbβ3 caused by ERp46 deficiency to the normal level. TMX1 inhibited the reductase activity of ERp46 in a concentration-dependent manner. Using thiol labeling approach, we observed that TMX1 oxidized thiols in ERp46. Besides, TMX1 deficiency increased the thiol in ERp46. Furthermore, TMX1 not only oxidized ERp46-reduced αIIbβ3 but also oxidized ERp46 itself, consequently inhibiting its reduction of αIIbβ3. These results indicated that TMX1 counterbalances the effect of ERp46 in the process of platelet activation.

Conclusion(s): TMX1 negatively regulates platelet activation through the oxidation of ERp46 to suppress its reduction of αIIbβ3 disulfide bonds. Besides, TMX1 directly oxidizes αIIbβ3 disulfides that is reduced by ERp46. These new findings demonstrate a novel mechanism formed by the positive and negative disulfide isomerases, fine-tuning integrin αIIbβ3 function.