Identification of disulfide bond-linking sites in biosynthesized platelet factor 4 by establishing a partial
Wenrui Hu1,2, Ming Li2, Peize Wu2
1College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P.R. China. luosz@mail.buct.edu.cn.
Insights
This study produced recombinant human Platelet Factor 4 (PF4) using a bacterial system. The characterized PF4 is identical to native PF4 and retains biological activity, crucial for heparin-induced thrombocytopenia diagnostics.
Area of Science:
- Biochemistry
- Molecular Biology
- Hematology
Background:
- Platelet Factor 4 (PF4) is vital in coagulation and forms complexes with heparin, implicated in heparin-induced thrombocytopenia (HIT).
- Accurate PF4 characterization is essential for HIT diagnosis and management, with recent findings suggesting roles in cognitive function.
- Current diagnostic tests for HIT rely on detecting antibodies against PF4/heparin complexes.
Purpose of the Study:
- To establish a bacterial expression system for producing recombinant human PF4 (rhPF4).
- To comprehensively characterize the produced rhPF4, ensuring its identity and biological activity.
- To determine the disulfide bond connectivity critical for PF4 structure and function.
Main Methods:
- Bacterial expression system for rhPF4 production.
- Liquid chromatography-high resolution mass spectrometry for sequence and disulfide connectivity analysis.
- In vitro chemotaxis assay to confirm biological activity.
Main Results:
- Efficient production of rhPF4 achieved.
- rhPF4 confirmed to be identical to native PF4 in sequence and disulfide connectivity.
- rhPF4 demonstrated biological activity in chemotaxis assays.
- Disulfide bond connectivity determined as Cys10-Cys36 and Cys12-Cys52 using partial reduction.
Conclusions:
- The bacterial expression system provides a reliable source of rhPF4.
- Characterized rhPF4 serves as a valuable standard for HIT diagnostics and research.
- Understanding PF4 disulfide bonds is key to its structural integrity and function.
Abstract:
Platelet factor 4 (PF4), a specific protein primarily found in megakaryocytes and platelet α-granules, plays an essential role in the coagulation process. It carries a high positive charge and thus has a unique ability to readily form complexes with negatively charged heparin. This interaction between PF4 and heparin plays a crucial role in platelet aggregation and thrombosis, resulting in heparin-induced thrombocytopenia (HIT). HIT is often diagnosed through various diagnostic tests that utilize exogenous PF4 detecting antibodies against PF4/heparin complexes. Besides, PF4 was recently found to have the potential to restore cognitive function. Therefore, a comprehensive characterization of biosynthetic PF4 standards is crucial for the diagnosis and management of HIT. In this study, a bacterial expression system was established to efficiently produce recombinant human PF4 (rhPF4). This PF4 was characterized using liquid chromatography-high resolution mass spectrometry, confirming it is completely identical to native PF4 in terms of disulfide connectivity and sequence. The in vitro chemotaxis assay indicates that it possesses biological activity. Furthermore, PF4 contains two disulfide bonds, which are crucial for its structural integrity and function. A partial reduction method was successfully developed to assign the disulfide bond connectivity as Cys10-Cys36 and Cys12-Cys52.
