SERPINC1 p.M313T Variant Induces Aberrant O-Glycosylation and Leads to Conformational Instability-Related Transient...

Area of Science:

• Genetics and Molecular Biology
• Hematology
• Biochemistry

Background:

• Congenital antithrombin (AT) deficiency, often due to SERPINC1 variants, is a significant risk factor for venous thromboembolism (VTE).
• The SERPINC1 p.M313T variant was previously identified in VTE patients with normal AT levels, necessitating investigation into its mechanism.
• Understanding the pathogenicity of this variant is crucial for diagnosing and managing VTE risk.

Purpose of the Study:

• To elucidate the pathogenetic mechanism of the SERPINC1 p.M313T variant.
• To investigate the structural and functional consequences of the p.M313T substitution in antithrombin.
• To assess the potential of this variant to cause transient AT deficiency and predispose individuals to thrombosis.

Main Methods:

• Utilized thrombin generation test (TGT), thermal stability assays, and native-urea PAGE.
• Performed in vitro protein expression, enzymatic assays, and glycosylation analysis.
• Conducted molecular dynamics simulations for structural analysis.

Main Results:

• AT from probands showed reduced thermostability and increased denatured/latent forms.
• Recombinant AT-M313T displayed enhanced inhibitory activity but decreased stability and a propensity for latency.
• Abnormal O-linked glycosylation in the breach region and altered protein structure were confirmed.
• Molecular dynamics revealed a less compact structure with increased flexibility.

Conclusions:

• The SERPINC1 p.M313T variant presents a dual profile of high activity and low stability, contributing to transient AT deficiency.
• This variant may lead to underdiagnosis of AT deficiency, emphasizing the need for advanced diagnostic tools.
• Integrating methods like native-urea PAGE is vital for identifying structural AT abnormalities and assessing VTE risk.