Structure-Function Analysis of the Mcl-1 Protein Identifies a Novel Senescence-regulating Domain.

Abstract

Unlike other antiapoptotic Bcl-2 family members, Mcl-1 also mediates resistance to cancer therapy by uniquely inhibiting chemotherapy-induced senescence (CIS). In general, Bcl-2 family members regulate apoptosis at the level of the mitochondria through a common prosurvival binding groove. Through mutagenesis, we determined that Mcl-1 can inhibit CIS even in the absence of its apoptotically important mitochondrion-localizing domains. This finding prompted us to generate a series of Mcl-1 deletion mutants from both the N and C termini of the protein, including one that contained a deletion of all of the Bcl-2 homology domains, none of which impacted anti-CIS capabilities. Through subsequent structure-function analyses of Mcl-1, we identified a previously uncharacterized loop domain responsible for the anti-CIS activity of Mcl-1. The importance of the loop domain was confirmed in multiple tumor types, two in vivo models of senescence, and by demonstrating that a peptide mimetic of the loop domain can effectively inhibit the anti-CIS function of Mcl-1. The results from our studies appear to be highly translatable because we discerned an inverse relationship between the expression of Mcl-1 and of various senescence markers in cancerous human tissues. In summary, our findings regarding the unique structural properties of Mcl-1 provide new approaches for targeted cancer therapy.

• Authors: Abeba Demelash, Lukas W Pfannenstiel, Charles S Tannenbaum, Xiaoxia Li, Matthew F Kalady, Jennifer DeVecchio, Brian R Gastman
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 290 Issue 36 Pg. 21962-75 (Sep 04 2015) ISSN: 1083-351X [Electronic] United States
• PMID: 26205817 (Publication Type: Journal Article)
• Copyright: © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• Antibiotics, Antineoplastic
• MCL1 protein, human
• Myeloid Cell Leukemia Sequence 1 Protein
• Doxorubicin

Topics

• Aging (genetics)
• Animals
• Antibiotics, Antineoplastic (pharmacology)
• Caco-2 Cells
• Cell Line, Tumor
• Cellular Senescence (genetics)
• Colorectal Neoplasms (drug therapy, genetics, metabolism)
• Doxorubicin (pharmacology)
• Female
• HCT116 Cells
• HT29 Cells
• HeLa Cells
• Humans
• Immunoblotting
• Immunohistochemistry
• Mice, Nude
• Microscopy, Confocal
• Models, Molecular
• Mutagenesis, Site-Directed
• Myeloid Cell Leukemia Sequence 1 Protein (chemistry, genetics, metabolism)
• Protein Structure, Secondary
• Protein Structure, Tertiary
• RNA Interference
• Structure-Activity Relationship
• Xenograft Model Antitumor Assays