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Phosphatidylserine as an anchor for plasminogen and its plasminogen receptor, histone H2B, to the macrophage surface

R Das1, E F Plow

  • 1Department of Molecular Cardiology, Cleveland Clinic, Joseph J. Jacobs Center for Thrombosis and Vascular Biology, Cleveland, OH 44195, USA.

Journal of Thrombosis and Haemostasis : JTH
|November 3, 2010
PubMed
Abstract

Insights

Histone H2B (H2B) binds to macrophage surfaces via phosphatidylserine (PS) interaction, facilitated by L-type Ca(2+) channels. This PS-H2B complex enhances plasminogen (Plg) binding, crucial for cell migration.

Area of Science:

  • Cell Biology
  • Immunology
  • Biochemistry

Background:

  • Cell surface plasminogen (Plg) receptors (Plg-Rs) mediate Plg activation and macrophage migration.
  • Histone H2B (H2B) functions as a Plg-R, with its surface expression increased during monocyte-to-macrophage differentiation.
  • This differentiation pathway involves L-type Ca(2+) channels and intracellular Ca(2+).

Purpose of the Study:

  • Investigate the mechanism of H2B retention on the macrophage surface, as H2B lacks a transmembrane domain.
  • Elucidate the role of phosphatidylserine (PS) in H2B cell surface anchoring.
  • Determine the involvement of L-type Ca(2+) channels in H2B surface expression and Plg binding.

Main Methods:

  • THP-1 monocytoid cells were differentiated or induced into apoptosis.
  • Flow cytometry and cell surface biotinylation followed by Western blotting were employed.
  • Interactions between Plg binding, H2B surface expression, and PS exposure were quantified.

Main Results:

  • H2B directly binds to PS through electrostatic interactions.
  • Inhibition of PS binding (using anti-PS, annexin V, or protein S) reduced H2B-PS interaction and Plg binding.
  • L-type Ca(2+) channels significantly influenced PS exposure, H2B surface expression, and Plg binding during differentiation and apoptosis.

Conclusions:

  • H2B tethers to differentiated or apoptotic cell surfaces via PS interaction.
  • L-type Ca(2+) channels regulate PS exposure on these cells.
  • Exposed PS serves as a binding site for H2B, subsequently facilitating Plg binding.

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