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Proteolytic activation of pro-macrophage-stimulating protein by hepsin

Rajkumar Ganesan1, Ganesh A Kolumam, S Jack Lin

  • 1Department of Early Discovery Biochemistry, Genentech, Inc., 1 DNA Way, MS #27, South San Francisco, CA 94080, USA.

Molecular Cancer Research : MCR
|August 31, 2011
PubMed

Insights

Hepsin protease efficiently activates macrophage-stimulating protein (MSP) by cleaving pro-MSP, enhancing its binding to the RON receptor. This activation influences cell signaling, migration, and immune responses, highlighting hepsin

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Background:

  • Macrophage-stimulating protein (MSP) is a growth factor that binds to the receptor tyrosine kinase RON.
  • The MSP/RON system regulates wound healing, tumor growth, and immune responses.
  • Activation of pro-MSP to its heterodimeric form is necessary for high-affinity RON binding.

Purpose of the Study:

  • To investigate the role of hepsin, a serine protease, in the activation of pro-MSP.
  • To determine the efficiency of hepsin in cleaving pro-MSP compared to other known activators.
  • To explore the functional consequences of hepsin-mediated MSP activation on cell signaling and immune cells.

Main Methods:

  • Recombinant hepsin was used to cleave pro-MSP in vitro.
  • Binding affinity of cleaved MSP to RON-Fc fusion protein was measured using surface plasmon resonance.
  • Pro-MSP activation by hepsin-overexpressing cancer cells and subsequent signaling events (MAPK, Akt phosphorylation) were analyzed.
  • Effects of hepsin-activated MSP on macrophage chemotaxis and nitric oxide production were assessed.

Main Results:

  • Recombinant hepsin efficiently cleaved pro-MSP at the consensus site Arg(483)-Val(484), surpassing MT-SP1 and HGFA in activity.
  • Hepsin-cleaved MSP exhibited high-affinity binding to RON (K(D) = 10.3 nmol/L), unlike uncleavable pro-MSP.
  • Hepsin-overexpressing prostate cancer cells activated pro-MSP, leading to RON-mediated downstream signaling.
  • Hepsin-activated MSP induced macrophage chemotaxis and suppressed lipopolysaccharide-induced nitric oxide production.

Conclusions:

  • Hepsin is a highly efficient activator of pro-MSP, generating a high-affinity ligand for RON.
  • Hepsin-mediated MSP activation plays a significant role in regulating cellular functions, including cancer cell signaling and immune cell behavior.
  • The MSP/RON pathway, regulated by hepsin, is implicated in tissue homeostasis and disease pathologies like cancer and immune disorders.

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