Advanced fluorescence spectroscopy to unravel functional oligomerization of a newly discovered Ca2+ channel and its role in heart failure.

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Endoplasmic reticulum (ER) homeostasis is becoming an increasingly interesting target in heart failure, since accumulation of misfolded or unfolded proteins can easily lead to ER stress, which in turn can play an important role in the development of cardiovascular diseases. ER transmembrane proteins can play prominent signalling roles that influence cell death or survival. Mitsugumin 23 (MG23), is a newly discovered endoplasmic/sarcoplasmic reticulum (ER/SR) transmembrane protein thought to be oligomeric in nature. We suggest that the dynamic oligomerization behaviour of MG23 controls its functional role. Our latest data suggest a role for MG23 in cardiac fibrosis, SR Ca2+ leak and the early stages of heart failure. This makes MG23 a novel and timely target for further in-depth study to unravel the molecular role played by its reported oligomerization and provide a better understanding of its potential druggability. Although our ability to study oligomerization of plasma membrane integral proteins has greatly advanced over the last few years, these approaches rely on extreme optical sectioning, which is not amenable to internal organelles such as the ER/SR. The aim of this PhD project is to develop and apply spatial-temporal molecular brightness approaches using confocal microscopy to address the problem of the oligomerization dynamics of MG23 in pathophysiological conditions. The use of fluorescence fluctuation spectroscopy offers promise to study homo-oligomerization in crowded systems, where the visualization of individual molecules is challenged either by protein density and/or by the local geometry of the sample. Using a combination of molecular biology, electrophysiology, heart failure models and advanced microscopy techniques, I will visualize MG23 functional oligomerization in cardiac cells, unravel MG23 oligomerization in heart failure conditions, and correlate MG23 oligomerization to cardiac cell pathology, specifically apoptosis and fibrosis. This project will develop a toolbox to study ER membrane protein oligomerization, with ramifications to the broader study of the unfolded protein response pathway in heart failure.