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Identification of the BCL2/adenovirus E1B-19K protein-interacting protein 2 (BNIP-2) as a granzyme B target during

Gina B Scott1, Paul A Bowles, Erica B Wilson

  • 1Leeds Institute of Molecular Medicine, University of Leeds, St. James's University Hospital, UK.

The Biochemical Journal
|August 14, 2010
PubMed

Insights

Cytotoxic lymphocytes use granzymes to induce apoptosis. Researchers found Granzyme B cleaves BNIP-2, a key protein in cell death, revealing a new pathway in immune responses.

Area of Science:

  • Immunology
  • Cell Biology
  • Biochemistry

Background:

  • Cytotoxic lymphocytes eliminate infected cells and tumors using granzymes.
  • Granzyme B induces apoptosis by cleaving cellular proteins, activating caspases, and causing mitochondrial depolarization.

Purpose of the Study:

  • To investigate the role of BNIP-2 (BCL2/adenovirus E1B-19K protein-interacting protein 2) in cytotoxic lymphocyte-mediated apoptosis.
  • To identify and characterize Granzyme B cleavage sites in BNIP-2.

Main Methods:

  • Bioinformatics analysis to predict Granzyme B cleavage sites in BNIP-2.
  • In vitro cleavage assays using recombinant BNIP-2.
  • Analysis of endogenous BNIP-2 cleavage during NK cell-mediated killing of tumor cells.
  • Gene silencing and expression studies of BNIP-2 and BID (BH3-interacting domain death agonist).

Main Results:

  • A candidate Granzyme B cleavage site was identified in BNIP-2 using bioinformatics.
  • Granzyme B directly cleaved recombinant and endogenous BNIP-2 in a caspase-independent manner at the predicted site.
  • Expression of BNIP-2 or its cleaved form induced apoptosis, with subsequent caspase-dependent cleavage at a different site.
  • Inhibition of BNIP-2 or BID expression did not affect susceptibility to NK cell-mediated killing, indicating functional redundancy.

Conclusions:

  • Granzyme B targets BNIP-2 for cleavage, contributing to the pro-apoptotic function of cytotoxic lymphocytes.
  • Redundancy exists in the pro-apoptotic pathways activated by cytotoxic lymphocytes, involving proteins like BNIP-2 and BID.
  • This redundancy enhances the efficiency of immune-mediated clearance of infected cells and tumors by minimizing escape routes.

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