Thursday, April 25, 2024
4/25/2024
The reversible control of enzyme activity is one of the cornerstone features enabling life. Cycles of protein phosophorylation and de-phosphorylation have been appreciated for decades to regulate enzymes, and the pharmacological inhibition of protein kinases and phosphatases has furnished a biotech industry intent on treating various human diseases for nearly as long. One major drawback to this strategy is that the enzymes that regulate protein phosphorylation represent perhaps 5 % of the human proteome, such that the vast majority of aberrant proteins responsible for human disease have remained undruggable. More recently, drugs have been invented that induce proximity between a disease-causing protein and an enzyme called a ubiquitin ligase that promotes the destruction of the problematic protein. Indeed, this new drug modality is feeding a billion dollar per year industry push to employ ubiquitin ligases to treat various human diseases including breast and prostate cancers as well as multiple myeloma, to name a few. Most of these efforts have been utilizing a family of enzymes called the Cullin-RING ligases (CRLs). With some 200 members in humans, the CRLs collectively control approximately 20 % of ubiquitin-dependent protein degradation in cells. As such, an appreciation for how these enzymes are regulated is of considerable interest to a wide audience from the scientific community. Similar to the paradigm of protein phosphorylation, the control of CRLs is believed to be determined predominantly through their reversible modification with a protein called NEDD8. And while human CRLs are known to partner with at least 7 additional enzymes, which we refer to as ubiquitin-carrying enzymes (UCEs), that help promote CRL- dependent protein substrate degradation, it also was believed that UCEs act promiscuously towards CRLs which would preclude CRL regulation at the level of CRL-UCE interaction. However, CRL-UCE specificity is strongly implied by the recent structure of an active CRL. Preliminary results here indicate that CRL-UCE specificity endows these pairs with exceptionally rapid rates of ubiquitin transfer and with the capability of producing CRL substrates modified with unique poly-ubiquitin chain architectures, potentially providing an additional layer of control of CRL function beyond neddylation. In consideration of these observations, this application seeks to test the hypothesis that UCEs generally display specificity for CRL-substrate complexes, and that the biological purpose of these specific CRL-UCE pairs is to both enhance the rates of ubiquitin transfer from UCEs to CRL substrates as well as to uniquely code the poly-ubiquitin chain to promote outcomes including protein degradation or localization. The proposed studies will explore an entirely novel area of CRL biology, the specificity of UCEs for CRLs, utilizing proteomic and cell biological assays to complement a powerful, quantitative kinetics platform. These studies will illuminate how CRL activities are regulated and support a new drug modality that harnesses the power of CRLs to degrade disease-causing proteins.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).
