A structural insight of NRZ mediated apoptosis regulation in zebrafish

Suraweera CD1, Caria S1, Jarva M1, Hinds MG2 and Kvansakul M1

  1. 1Department of Biochemistry & Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
  2. Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Australia.

Bcl-2 family proteins play a crucial role in regulating apoptosis, a process critical for development, eliminating damaged or infected cells, host-pathogen interactions and in disease. Dysregulation of Bcl-2 proteins elicits an expansive cell survival mechanism promoting cell migration, invasion and metastasis. Through a network of intra-family protein-protein interactions Bcl-2 family members regulate the release of cell death factors from mitochondria. NRZ is a novel zebrafish pro-survival Bcl-2 orthologue resident on mitochondria and the endoplasmic reticulum (ER). However, the mechanism of NRZ apoptosis inhibition has not yet been clarified. Here, we examined the interactions of NRZ with pro-apoptotic members of the Bcl-2 family. We show that NRZ binds almost all zebrafish pro-apoptotic proteins and displays a broad range of affinities. Furthermore, we define the structural basis for apoptosis inhibition of NRZ by solving the crystal structure of both apo-NRZ and a holo form bound to a peptide spanning the binding motif of the proapoptotic zBad, a BH3-only protein orthologous to mammalian Bad. The crystal structure of NRZ revealed that it adopts the conserved Bcl-2 like fold observed for other cellular pro-survival Bcl-2 proteins and employs the canonical ligand binding groove to bind Bad BH3 peptide. Our findings provide a detailed mechanistic understanding for NRZ mediated antiapoptotic activity in zebrafish and suggest that NRZ likely occupies a unique mechanistic role in zebrafish apoptosis regulation.