The voltage-gated calcium channels (Cav) regulate calcium influx into the cell. The high voltage Cav1 subfamily comprise four heteromeric channels (Cav1.1-1.4). Cav1 channels are mutated in a diverse range of rare disorders with different inheritance patterns (dominant/ recessive; autosomal/ X-linked) and affect a spectrum of organ systems (e.g. cardiovascular, neurological, ocular, and hearing). Currently, a molecular diagnosis is only possible for a limited number of these conditions as the pathogenic variants and molecular pathways involved remain largely undefined. Despite the refinement of informatics, there is no one in silico tool that can accurately discern clinically relevant variants from benign ones. This project used an integrated functional and informatics approach to improve the rate of molecular diagnoses for Cav1 channelopathies by empirically verifying informatic pathogenicity predictions of variants in the Cav1.4 channel. The integrated data were then used to inform interpretation of the mechanism of pathogenicity in the other Cav1 channel family members and predict the amenability to therapeutic approaches. The work presented in this thesis identified that although Cav1 channels function in a similar way, their pathogenic mechanisms are different as both hypoactive and hyperactive protein dysfunctions are pathogenic. This thesis further refines informatic tools and demonstrates that they are inaccurate for pathogenic predictions of rare coding sequence variations in unresolved protein regions. These results show that incomplete congenital stationary night blindness (iCSNB) is caused by hypomorphic variants in the Cav1.4Î±-encoding gene that are degraded by the proteasome. This discovery identified a group of mechanistically similar mutations in all four Cav1 genes and uncovered a suitable target for drug discovery. Significantly, this group of mutations are amenable to functional rescue using a class of clinically approved proteasome inhibitors; Bortezomib, Ixazomib and Carfilzomib. Collectively, this study shows that Bortezomib treatment can restore the function and protein levels of hypomorphic Cav1 mutations associated with Brugada syndrome, malignant hyperthermia, iCSNB, and hearing impairment. This provides a potential therapeutic opportunity that has broad applicability across disease groupings.
|Date of Award||1 Aug 2022|
- The University of Manchester
|Supervisor||Graeme Black (Supervisor), Forbes Manson (Supervisor) & Simon Lovell (Supervisor)|
- Protein degradation
- L-type calcium channels
- Incomplete congenital stationary night blindness