Deficiency in the membrane protein Tmbim3a/Grinaa initiates cold-induced ER stress and cell death by activating an intrinsic apoptotic pathway in zebrafish

Chen, K., Li, X., Song, G., Zhou, T., Long, Y., Li, Q., Zhong, S., Cui, Z.
The Journal of biological chemistry   294(30): 11445-11457 (Journal)
Registered Authors
Chen, Kai, Cui, Zongbin, Li, Qing, Li, Xixi, Long, Yong, Song, Guili
Apoptosis, Calcium homeostasis, Cold exposure, Grinaa, apoptosis, calcium intracellular release, endoplasmic reticulum stress (ER stress), endoplasmic reticulum stress; Calcium homeostasis, stress response, zebrafish
MeSH Terms
  • Animals
  • Apoptosis*/drug effects
  • Boron Compounds/pharmacology
  • Chelating Agents/pharmacology
  • Cold Temperature*
  • Egtazic Acid/analogs & derivatives
  • Egtazic Acid/pharmacology
  • Embryo, Nonmammalian/drug effects
  • Endoplasmic Reticulum Stress*
  • Membrane Proteins/genetics
  • Membrane Proteins/metabolism*
  • Mutation
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases/metabolism
  • Subcellular Fractions/metabolism
  • Unfolded Protein Response
  • Zebrafish/embryology
  • Zebrafish/growth & development
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism*
31171717 Full text @ J. Biol. Chem.
Most members of the family of proteins containing a transmembrane BAX inhibitor motif (TMBIM) have anti-apoptotic activity, but their in vivo functions and intracellular mechanisms remain obscure. Here, we report that zebrafish Tmbim3a/Grinaa functions in the prevention of cold-induced endoplasmic reticulum (ER) stress and apoptosis. Using a gene-trapping approach, we obtained a mutant zebrafish line in which the expression of the tmbim3a/grinaa gene is disrupted by a Tol2 transposon insertion. Homozygous tmbim3a/grinaa mutant larvae exhibited time-dependently increased mortality and apoptosis under cold exposure (at 16ºC). Mechanistically, using immunofluorescence, fluorescence-based assessments of intracellular/mitochondrial Ca²+ levels, mitochondrial membrane potential measurements, and Ca²+-ATPase assays, we found that cold exposure suppresses sarcoplasmic/ER Ca²+-ATPase (SERCA) activity and induces the unfolded protein response (UPR) and ER stress. We also found that the cold-induced ER stress is increased in homozygous tmbim3a/grinaa mutant embryos. The cold-stress hyper-sensitivity of the tmbim3a/grinaa mutants was tightly associated with disrupted intracellular Ca²+ homeostasis, followed by mitochondrial Ca²+ overload and cytochrome c release, leading to the activation of caspase 9- and caspase 3-mediated intrinsic apoptotic pathways. Treatment of zebrafish larvae with the intracellular Ca²+ chelator BAPTA-AM or with 2-APB, an inhibitor of the calcium-releasing protein IP3 receptor (IP3R), alleviated cold-induced cell death. Together, these findings unveil a key role of Tmbim3a/Grinaa in relieving cold-induced ER stress and in protecting cells against caspase 9- and 3-mediated apoptosis during zebrafish development.
Genes / Markers
Show all Figures
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Engineered Foreign Genes