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Histone H2B as a functionally important plasminogen receptor on macrophages
Riku Das1, Tim Burke, Edward F Plow
1Joseph J. Jacobs Center for Thrombosis and Vascular Biology, Department of Molecular Cardiology, Cleveland Clinic, OH, USA.
Abstract:
Plasminogen (Plg) facilitates inflammatory cell recruitment, a function that depends upon its binding to Plg receptors (Plg-Rs). However, the Plg-Rs that are critical for cell migration are not well defined. Three previously characterized Plg-Rs (alpha-enolase, annexin 2, and p11) and a recently identified Plg-R (histone H2B [H2B]) were assessed for their contribution to Plg binding and function on macrophages. Two murine macrophage cell lines (RAW 264.7 and J774A.1) and mouse peritoneal macrophages induced by thioglycollate were analyzed. All 4 Plg-Rs were present on the surface of these cells and showed enhanced expression on the thioglycollate-induced macrophages compared with peripheral blood monocytes. Using blocking Fab fragments to each Plg-R, H2B supported approximately 50% of the Plg binding capacity, whereas the other Plg-Rs contributed less than 25%. Anti-H2B Fab also demonstrated a major role of this Plg-R in plasmin generation and matrix invasion. When mice were treated intravenously with anti-H2B Fab, peritoneal macrophage recruitment in response to thioglycollate was reduced by approximately 45% at 24, 48, and 72 hours, with no effect on blood monocyte levels. Taken together, these data suggest that multiple Plg-Rs do contribute to Plg binding to macrophages, and among these, H2B plays a very prominent and functionally important role.
Insights
Histone H2B is a key receptor for plasminogen (Plg) on macrophages, significantly impacting inflammatory cell recruitment and function. This study highlights H2B
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Plasminogen (Plg) binding to plasminogen receptors (Plg-Rs) is crucial for inflammatory cell recruitment.
- The specific Plg-Rs involved in macrophage migration remain incompletely understood.
Purpose of the Study:
- To investigate the contribution of four Plg-Rs (alpha-enolase, annexin 2, p11, and histone H2B [H2B]) to Plg binding and function on macrophages.
- To determine the critical role of H2B in Plg-mediated macrophage recruitment and inflammatory responses.
Main Methods:
- Analysis of Plg-R expression on murine macrophage cell lines and primary macrophages.
- Utilized blocking Fab fragments to quantify the contribution of individual Plg-Rs to Plg binding.
- Assessed the impact of anti-H2B Fab on plasmin generation, matrix invasion, and in vivo macrophage recruitment.
Main Results:
- All four Plg-Rs were detected on macrophages, with enhanced expression on thioglycollate-induced cells.
- Histone H2B (H2B) accounted for approximately 50% of Plg binding capacity, significantly more than other tested Plg-Rs.
- Blocking H2B function reduced plasmin generation, matrix invasion, and peritoneal macrophage recruitment by about 45% in vivo.
Conclusions:
- Multiple Plg-Rs contribute to Plg binding on macrophages.
- Histone H2B (H2B) plays a prominent and functionally critical role in Plg binding, plasmin generation, and inflammatory macrophage recruitment.
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