Date of Award
9-2012
Document type
dissertation
Access Type
Open Access Dissertation
Degree Name
Doctor of Philosophy (PhD)
Degree Program
Chemistry
First Advisor
Jeanne A. Hardy
Second Advisor
Vincent M. Rotello
Third Advisor
Craig T. Martin
Subject Categories
Chemistry
Abstract
Caspases are cysteine proteases best known for their controlling roles in apoptosis and inflammation. Caspase-6 has recently been shown to play a key role in the cleavage of neurodegenerative substrates that causes Huntington and Alzheimer's Disease, heightening interest in caspase-6 and making it a drug target. All thirteen human caspases have related specificities for binding and cleaving substrate, so achieving caspase-specific regulation at the active site has been extremely challenging if not impossible. We have determined the structures of four unliganded forms of caspase-6, which attain a novel helical structure not observed in any other caspases. In this conformation, rotation of the 90's helix results in formation of a cavity that can function as an allosteric site, locking caspase-6 into an inactive conformation. We are using this cavity to look for chemical ligands that target this cavity and maintain caspase-6 in the inactive, helical conformation. We found that known allosteric inhibitors of caspase-3 and -7 also inhibit caspase-6 through a cavity at the dimer interface. We have determined new structures of a phosphomimetic state and a zinc-bound conformation of caspase-6, which show the molecular details of two additional allosteric sites. The phosphomimetic form of caspase-6 inactivates caspase-6 by disrupting formation of the substrate binding-groove by steric clash of the phosphorylated residue with P201 in the L2' loop. Another allosteric site was found on the "back" of caspase-6 that coordinates a zinc molecule that leads to inactivation. In total we have uncovered four independent allosteric sites in caspase-6, structurally characterized inhibition from these sites and demonstrated that each of these sites might be targeted for caspase-6 specific inhibition by synthetic or natural-product ligands.
DOI
https://doi.org/10.7275/3528288
Recommended Citation
Velazquez-Delgado, Elih M., "Allosteric Regulation of Caspase-6 Proteolytic Activity" (2012). Open Access Dissertations. 630.
https://doi.org/10.7275/3528288
https://scholarworks.umass.edu/open_access_dissertations/630