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Midkine binds to 37-kDa laminin binding protein precursor, leading to nuclear transport of the complex

R H Salama1, H Muramatsu, K Zou

  • 1Department of Biochemistry, Nagoya University School of Medicine, 65 Tsurumai-cho, Nagoya, Showa-ku, 466-8550, Japan.

Experimental Cell Research
|October 13, 2001
PubMed

Insights

Midkine (MK) protein binds to laminin binding protein precursor (LBP). This interaction causes LBP to move into the nucleus within cancer cells, suggesting a novel molecular mechanism.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Midkine (MK) is a multifunctional protein involved in cell survival and migration.
  • Laminin binding protein precursor (LBP) is a precursor to the 67-kDa laminin receptor.
  • LBP is typically found in the cytoplasm, with some presence at the cell surface.

Purpose of the Study:

  • To investigate the interaction between Midkine (MK) and laminin binding protein precursor (LBP).
  • To determine the effect of MK binding on LBP localization within CMT-93 mouse rectal carcinoma cells.

Main Methods:

  • Binding assays using MK and LBP-glutathione-S-transferase fusion protein.
  • Immunostaining with anti-LBP antibody to determine LBP localization.
  • Cell attachment assays to verify cell surface LBP.
  • Observation of LBP and MK localization after MK addition to cell cultures.

Main Results:

  • MK binds to LBP with high affinity (K(d) = 1.1 nM).
  • Binding is inhibited by laminin, anti-LBP, amyloid beta-peptide, and heparin.
  • In CMT-93 cells, MK addition induced nuclear translocation of LBP, coinciding with MK's nuclear transport.
  • A portion of LBP was confirmed to be at the cell surface, mediating cell attachment to laminin.

Conclusions:

  • Midkine directly interacts with laminin binding protein precursor.
  • The MK-LBP interaction facilitates the translocation of LBP into the nucleus.
  • This molecular complex movement suggests a novel signaling pathway involving MK and LBP.

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