Thioflavin S (NSC71948) interferes with Bcl-2-associated athanogene (BAG-1)-mediated protein-protein interactions.
The C-terminal BAG domain is thought to play a key role in BAG-1-induced survival and proliferation by mediating protein-protein interactions, for example, with heat shock proteins HSC70 and HSP70, and with RAF-1 kinase. Here, we have identified thioflavin S (NSC71948) as a potential small-molecule chemical inhibitor of these interactions. NSC71948 inhibited the interaction of BAG-1 and HSC70 in vitro and decreased BAG-1:HSC70 and BAG-1:HSP70 binding in intact cells. NSC71948 also reduced binding between BAG-1 and RAF-1, but had no effect on the interaction between two unrelated proteins, BIM and MCL-1. NSC71948 functionally reversed the ability of BAG-1 to promote vitamin D3 receptor-mediated transactivation, an activity of BAG-1 that depends on HSC70/HSP70 binding, and reduced phosphorylation of p44/42 mitogen-activate protein kinase. NSC71948 can be used to stain amyloid fibrils; however, structurally related compounds, thioflavin T and BTA-1, had no effect on BAG-1:HSC70 binding, suggesting that structural features important for amyloid fibril binding and inhibition of BAG-1:HSC70 binding may be separable. We demonstrated that NSC71948 inhibited the growth of BAG-1 expressing human ZR-75-1 breast cancer cells and wild-type, but not BAG-1-deficient, mouse embryo fibroblasts. Taken together, these data suggest that NSC71948 may be a useful molecule to investigate the functional significance of BAG-1 C-terminal protein interactions. However, it is important to recognize that NSC71948 may exert additional "off-target" effects. Inhibition of BAG-1 function may be an attractive strategy to inhibit the growth of BAG-1-overexpressing cancers, and further screens of additional compound collections may be warranted.
Sharp
Adam
A
Cancer Research UK Centre, Cancer Sciences Division, University of Southampton School of Medicine, Southampton General Hospital, Southampton, United Kingdom.
Crabb
Simon J
SJ
Johnson
Peter W M
PW
Hague
Angela
A
Cutress
Ramsey
R
Townsend
Paul A
PA
Ganesan
A
A
Packham
Graham
G
D000818:Animals; D052160:Benzothiazoles; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005456:Fluorescent Dyes / Q000494:pharmacology*; D050883:HSC70 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D010957:Plasmids / Q000235:genetics; D018167:Receptors, Calcitriol / Q000187:drug effects; D012710:Serum Albumin, Bovine / Q000737:chemistry; D054852:Small Molecule Libraries; D013844:Thiazoles / Q000494:pharmacology*; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism*
C091732:BCL2-associated athanogene 1 protein; D052160:Benzothiazoles; D004268:DNA-Binding Proteins; D005456:Fluorescent Dyes; D050883:HSC70 Heat-Shock Proteins; D018167:Receptors, Calcitriol; D054852:Small Molecule Libraries; D013844:Thiazoles; D014157:Transcription Factors; C009462:thioflavin T; D012710:Serum Albumin, Bovine; D008156:Luciferases; D048049:Extracellular Signal-Regulated MAP Kinases
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