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Prohibitin binds to C3 and enhances complement activation

Suresh Mishra1, Saby Moulik, Liam J Murphy

  • 1Departments of Physiology & Internal Medicine, University of Manitoba, Winnipeg R3E 0W3, Canada. mishra@cc.umanitoba.ca

Molecular Immunology
|October 31, 2006
PubMed

Insights

Circulating Prohibitin (PHB1) protein binds to complement component C3, enhancing innate immunity. This protein activates complement and aids in cell lysis, suggesting a novel immune function.

Area of Science:

  • Biochemistry
  • Immunology
  • Cell Biology

Background:

  • Prohibitin (PHB1) is a multifunctional protein found in circulation.
  • Its role in innate immunity is not well understood.

Purpose of the Study:

  • To investigate the binding partners of circulating PHB1.
  • To determine the functional consequences of PHB1 binding to its partners.

Main Methods:

  • Crosslinking, immunoprecipitation, and proteomic analysis were used to identify PHB1 binding partners.
  • Solid-phase binding assays quantified PHB1-C3 interaction.
  • Complement activation assays assessed PHB1's effect on erythrocyte lysis.

Main Results:

  • PHB1 was found to bind to fragments of complement component C3.
  • The dissociation constant for PHB1-C3 binding was approximately 90 fmol/L.
  • PHB1 enhanced complement activation and erythrocyte lysis in a C3-dependent manner, unlike PHB2.

Conclusions:

  • PHB1 directly binds to and activates C3.
  • PHB1 possesses a previously unrecognized role in the innate immune system through complement activation.

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