Cellular and Molecular Life Sciences

, Volume 70, Issue 7, pp 1171–1183

The selective BH4-domain biology of Bcl-2-family members: IP3Rs and beyond

  • Giovanni Monaco
  • Tim Vervliet
  • Haidar Akl
  • Geert Bultynck
Review

DOI: 10.1007/s00018-012-1118-y

Cite this article as:
Monaco, G., Vervliet, T., Akl, H. et al. Cell. Mol. Life Sci. (2013) 70: 1171. doi:10.1007/s00018-012-1118-y

Abstract

Anti-apoptotic Bcl-2-family members not only neutralize pro-apoptotic proteins but also directly regulate intracellular Ca2+ signaling from the endoplasmic reticulum (ER), critically controlling cellular health, survival, and death initiation. Furthermore, distinct Bcl-2-family members may selectively regulate inositol 1,4,5-trisphosphate receptor (IP3R): Bcl-2 likely acts as an endogenous inhibitor of the IP3R, preventing pro-apoptotic Ca2+ transients, while Bcl-XL likely acts as an endogenous IP3R-sensitizing protein promoting pro-survival Ca2+ oscillations. Furthermore, distinct functional domains in Bcl-2 and Bcl-XL may underlie the divergence in IP3R regulation. The Bcl-2 homology (BH) 4 domain, which targets the central modulatory domain of the IP3R, is likely to be Bcl-2’s determining factor. In contrast, the hydrophobic cleft targets the C-terminal Ca2+-channel tail and might be more crucial for Bcl-XL’s function. Furthermore, one amino acid critically different in the sequence of Bcl-2’s and Bcl-XL’s BH4 domains underpins their selective effect on Ca2+ signaling and distinct biological properties of Bcl-2 versus Bcl-XL. This difference is evolutionary conserved across five classes of vertebrates and may represent a fundamental divergence in their biological function. Moreover, these insights open novel avenues to selectively suppress malignant Bcl-2 function in cancer cells by targeting its BH4 domain, while maintaining essential Bcl-XL functions in normal cells. Thus, IP3R-derived molecules that mimic the BH4 domain’s binding site on the IP3R may function synergistically with BH3-mimetic molecules selectivity suppressing Bcl-2’s proto-oncogenic activity. Finally, a more general role for the BH4 domain on IP3Rs, rather than solely anti-apoptotic, may not be excluded as part of a complex network of molecular interactions.

Keywords

Bcl-2Bcl-XLBH4-domain targetsInositol 1,4,5-trisphosphate receptorsCa2+ signalingApoptosis

Copyright information

© Springer Basel AG 2012

Authors and Affiliations

  • Giovanni Monaco
    • 1
  • Tim Vervliet
    • 1
  • Haidar Akl
    • 1
  • Geert Bultynck
    • 1
  1. 1.Laboratory of Molecular and Cellular Signaling, Department Cellular and Molecular MedicineKU LeuvenLeuvenBelgium