Tumor-Associated Mutations in Caspase‑6 Negatively Impact Catalytic Efficiency

• Published in: Biochemistry (Easton) Vol. 56; no. 34; pp. 4568 - 4577
• Main Authors: Dagbay, Kevin B, Hill, Maureen E, Barrett, Elizabeth, Hardy, Jeanne A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 29-08-2017
• Subjects: Amino Acid Substitution; Caspase 6 - chemistry; Caspase 6 - genetics; Caspase 6 - metabolism; Catalytic Domain; Humans; Mutation, Missense; Neoplasm Proteins - chemistry; Neoplasm Proteins - metabolism; Neoplasms - enzymology; Neoplasms - genetics
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/acs.biochem.7b00357

Unregulated, particularly suppressed programmed cell death is one of the distinguishing features of many cancer cells. The cysteine protease caspase-6, one of the executioners of apoptotic cell death, plays a crucial role in regulation of apoptosis. Several somatic mutations in the CASP6 gene in tumor tissues have been reported. This work explores the effect of CASP6 tumor-associated mutations on the catalytic efficiency and structure of caspase-6. In general, these mutations showed decreased overall rates of catalytic turnover. Mutations within 8 Å of the substrate-binding pocket of caspase-6 were found to be the most catalytically deactivating. Notably, the R259H substitution decreased activity by 457-fold. This substitution disrupts the cation−π stacking interaction between Arg-259 and Trp-227, which is indispensable for proper assembly of the substrate-binding loops in caspase-6. Sequence conservation analysis at the homologous position across the caspase family suggests a role for this cation−π stacking in the catalytic function of caspases generally. These data suggest that caspase-6 deactivating mutations may contribute to multifactorial carcinogenic transformations.