Targeting gamma-herpesvirus 68 Bcl-2-mediated down-regulation of autophagy.

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Su M, Mei Y, Sanishvili R, Levine B, Colbert CL, Sinha S

Targeting gamma-herpesvirus 68 Bcl-2-mediated down-regulation of autophagy.

J Biol Chem. 2014 Mar 21;289(12):8029-40. doi: 10.1074/jbc.M113.515361. Epub 2014 Jan 17.

PubMed ID
24443581 [ View in PubMed

gamma-herpesviruses (gammaHVs) are common human pathogens that encode homologs of the anti-apoptotic cellular Bcl-2 proteins, which are critical to viral reactivation and oncogenic transformation. The murine gammaHV68 provides a tractable in vivo model for understanding general features of these important human pathogens. Bcl-XL, a cellular Bcl-2 homolog, and the murine gammaHV68 Bcl-2 homolog, M11, both bind to a BH3 domain within the key autophagy effector Beclin 1 with comparable affinities, resulting in the down-regulation of Beclin 1-mediated autophagy. Despite this similarity, differences in residues lining the binding site of M11 and Bcl-XL dictate varying affinities for the different BH3 domain-containing proteins. Here we delineate Beclin 1 differential specificity determinants for binding to M11 or Bcl-XL by quantifying autophagy levels in cells expressing different Beclin 1 mutants and either M11 or Bcl-XL, and we show that a G120E/D121A Beclin 1 mutant selectively prevents down-regulation of Beclin 1-mediated autophagy by Bcl-XL, but not by M11. We use isothermal titration calorimetry to identify a Beclin 1 BH3 domain-derived peptide that selectively binds to M11, but not to Bcl-XL. The x-ray crystal structure of this peptide bound to M11 reveals the mechanism by which the M11 BH3 domain-binding groove accommodates this M11-specific peptide. This information was used to develop a cell-permeable peptide inhibitor that selectively inhibits M11-mediated, but not Bcl-XL-mediated, down-regulation of autophagy.

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