Thymidine Phosphorylase Mediates SARS-CoV-2 Spike Protein Enhanced Thrombosis in K18-hACE2TG Mice

• Published in: bioRxiv 2024-02
• Main Authors: Roytenberg, Renat, Hong, Yue, Dehart, Autumn, Kim, Eugene, Bai, Fang, Kim, Yongick, Denning, Krista, Kwei, Alec, Zhang, Quan, Liu, Jiang, Long, Zheng, Li, Wei
• Format: Article
• Language: English
• Subjects: COVID-19; Epithelial cells; Glycoprotein VI; Phosphorylase; Platelet aggregation; Platelet factor 4; Proteins; Severe acute respiratory syndrome coronavirus 2; siRNA; Spike protein; Stat3 protein; Thromboplastin; Thrombosis; Thymidine; Thymidine phosphorylase
• DOI: 10.1101/2024.02.23.581661

COVID-19, caused by SARS-CoV-2, is associated with arterial and venous thrombosis, thereby increasing mortality. SARS-CoV-2 spike protein (SP), a viral envelope structural protein, is implicated in COVID-19-associated thrombosis. However, the underlying mechanisms remain unknown. Thymidine phosphorylase (TYMP), a newly identified prothrombotic protein, is upregulated in the plasma, platelets, and lungs of patients with COVID-19 but its role in COVID-19-associated thrombosis is not defined. In this study, we found that wild-type SARS-CoV-2 SP significantly promoted arterial thrombosis in K18-hACE2TG mice. SP-accelerated thrombosis was attenuated by inhibition or genetic ablation of TYMP. SP increased the expression of TYMP, resulting in the activation of signal transducer and activator of transcription 3 (STAT3) in BEAS-2B cells, a human bronchial epithelial cell line. A siRNA-mediated knockdown of TYMP inhibited SP-enhanced activation of STAT3. Platelets derived from SP-treated K18-hACE2TG mice also showed increased STAT3 activation, which was reduced by TYMP deficiency. Activated STAT3 is known to potentiate glycoprotein VI signaling in platelets. While SP did not influence ADP- or collagen-induced platelet aggregation, it significantly shortened activated partial thromboplastin time and this change was reversed by TYMP knockout. Additionally, platelet factor 4 (PF4) interacts with SP, which also complexes with TYMP. TYMP enhanced the formation of the SP/PF4 complex, which may potentially augment the prothrombotic and procoagulant effects of PF4. We conclude that SP upregulates TYMP expression, and TYMP inhibition or knockout mitigates SP-enhanced thrombosis. These findings indicate that inhibition of TYMP may be a novel therapeutic strategy for COVID-19-associated thrombosis.Competing Interest StatementThe authors have declared no competing interest.