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SP-40,40 is a component of plasminogen activator inhibitor-1-binding protein and stabilizes plasminogen activator

N Choi-Miura1

  • 1Department of Physiological Chemistry, School of Pharmaceutical Sciences, Showa University, Tokyo, Japan. nammiura@pharm.showa-u.ac.jp

Biological & Pharmaceutical Bulletin
|February 24, 2001
PubMed

Insights

SP-40,40, a component of PAI-1-binding protein, stabilizes plasminogen activator inhibitor-1 (PAI-1) activity. This protein complex maintains PAI-1

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Protein Chemistry

Background:

  • Plasminogen activator inhibitor-1 (PAI-1) is a crucial regulator of the fibrinolytic system.
  • PAI-1 is known for its inherent instability, rapidly losing activity at physiological temperatures.
  • PAI-1-binding protein (PAI-1-BP) has been implicated in modulating PAI-1 function.

Purpose of the Study:

  • To identify the components of the PAI-1-binding protein (PAI-1-BP).
  • To investigate the effect of SP-40,40, a component of PAI-1-BP, on PAI-1 stability and activity.

Main Methods:

  • Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions.
  • Western blot analysis using specific antibodies.
  • Incubation of PAI-1 with SP-40,40 at 37°C and subsequent complex formation assays with tissue plasminogen activator (tPA).
  • Assays to measure inhibition of plasmin formation using plasminogen and urine plasminogen activator (uPA).

Main Results:

  • A PAI-1 complex was found to contain S-protein (vitronectin), PAI-1, and an unidentified 40-kDa protein.
  • Western blot analysis identified the 40-kDa protein as SP-40,40, indicating PAI-1-BP comprises S-protein and SP-40,40.
  • SP-40,40 significantly stabilized PAI-1 activity at 37°C, enabling complex formation with tPA and inhibition of plasmin generation.

Conclusions:

  • SP-40,40 plays a critical role in stabilizing PAI-1 activity, similar to S-protein.
  • The PAI-1-binding protein complex, containing SP-40,40, enhances the functional stability of PAI-1.
  • These findings contribute to understanding the regulatory mechanisms of the fibrinolytic system.

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