The carboxyl-terminal sequence of bim enables bax activation and killing of unprimed cells

Elife. 2020 Jan 24:9:e44525. doi: 10.7554/eLife.44525.

Abstract

The Bcl-2 family BH3 protein Bim promotes apoptosis at mitochondria by activating the pore-forming proteins Bax and Bak and by inhibiting the anti-apoptotic proteins Bcl-XL, Bcl-2 and Mcl-1. Bim binds to these proteins via its BH3 domain and to the mitochondrial membrane by a carboxyl-terminal sequence (CTS). In cells killed by Bim, the expression of a Bim mutant in which the CTS was deleted (BimL-dCTS) triggered apoptosis that correlated with inhibition of anti-apoptotic proteins being sufficient to permeabilize mitochondria isolated from the same cells. Detailed analysis of the molecular mechanism demonstrated that BimL-dCTS inhibited Bcl-XL but did not activate Bax. Examination of additional point mutants unexpectedly revealed that the CTS of Bim directly interacts with Bax, is required for physiological concentrations of Bim to activate Bax and that different residues in the CTS enable Bax activation and binding to membranes.

Keywords: BMK cells; Bcl-2 family proteins; MEF cells; apoptosis; cell biology; mitochondrial outer membrane permeabilization; molecular biophysics; none; primary murine neurons; structural biology.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / physiology*
  • Bcl-2-Like Protein 11* / chemistry
  • Bcl-2-Like Protein 11* / metabolism
  • Cells, Cultured
  • Cerebral Cortex / cytology
  • HCT116 Cells
  • HEK293 Cells
  • Humans
  • Mice, Inbred C57BL
  • Mitochondria / metabolism
  • Mitochondrial Membranes / metabolism
  • Neurons / cytology
  • Neurons / metabolism
  • Protein Domains
  • bcl-2-Associated X Protein* / chemistry
  • bcl-2-Associated X Protein* / metabolism

Substances

  • BAX protein, human
  • Bax protein, mouse
  • Bcl-2-Like Protein 11
  • Bcl2l11 protein, mouse
  • bcl-2-Associated X Protein