A novel BH3 ligand that selectively targets Mcl-1 reveals that apoptosis can proceed without Mcl-1 degradation.
Like Bcl-2, Mcl-1 is an important survival factor for many cancers, its expression contributing to chemoresistance and disease relapse. However, unlike other prosurvival Bcl-2-like proteins, Mcl-1 stability is acutely regulated. For example, the Bcl-2 homology 3 (BH3)-only protein Noxa, which preferentially binds to Mcl-1, also targets it for proteasomal degradation. In this paper, we describe the discovery and characterization of a novel BH3-like ligand derived from Bim, Bim(S)2A, which is highly selective for Mcl-1. Unlike Noxa, Bim(S)2A is unable to trigger Mcl-1 degradation, yet, like Noxa, Bim(S)2A promotes cell killing only when Bcl-x(L) is absent or neutralized. Furthermore, killing by endogenous Bim is not associated with Mcl-1 degradation. Thus, functional inactivation of Mcl-1 does not always require its elimination. Rather, it can be efficiently antagonized by a BH3-like ligand tightly engaging its binding groove, which is confirmed here with a structural study. Our data have important implications for the discovery of compounds that might kill cells whose survival depends on Mcl-1.
Lee
Erinna F
EF
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia.
Czabotar
Peter E
PE
van Delft
Mark F
MF
Michalak
Ewa M
EM
Boyle
Michelle J
MJ
Willis
Simon N
SN
Puthalakath
Hamsa
H
Bouillet
Philippe
P
Colman
Peter M
PM
Huang
David C S
DC
Fairlie
W Douglas
WD
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D006801:Humans; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008958:Models, Molecular; D008969:Molecular Sequence Data; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000737:chemistry / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000378:metabolism*; D016415:Sequence Alignment; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D008024:Ligands; C579094:Mcl1 protein, mouse; D008565:Membrane Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein