PROJECT SUMMARY
Mitochondria are central to cellular metabolism, signaling, protein homeostasis, immunity, and apoptosis. One
of the ways by which mitochondria respond effectively to changing mitochondrial and cellular needs is with
calcium signaling. Ca2+ ions enter the mitochondrial matrix through a protein channel called the mitochondrial
calcium uniporter (MCU) that resides on the inner membrane of the mitochondria. Altered MCU-mediated
mitochondrial calcium signaling is involved in a variety of human neurodegenerative diseases including
Parkinson's disease, Alzheimer's disease, and hereditary spastic paraplegia. Furthermore, these same diseases
have been shown to exhibit the hallmarks of mitochondrial protein stress, including elevated protein levels of
mitochondrial chaperones. Mitochondrial protein stress can be caused by misfolded or unfolded proteins
accumulating within the mitochondria. Preliminary studies in the Sancak Lab suggest that MCU-mediated
calcium signaling plays a critical role in facilitating the mitochondrial protein stress response. Data showing
increased MCU mRNA and protein during mitochondrial protein stress suggests that MCU is upregulated as part
of a mitochondrial protein stress response. Even more intriguingly, relative to WT and MCU rescue cell lines,
MCU knockout cells have lower baseline levels of mitochondrial chaperones and ATF4, a transcription factor
central to cellular stress responses. Furthermore, when mitochondrial protein stress is induced, the mRNA levels
of ATF4 and these chaperones increase much less than in WT or rescue cells. The central hypothesis of this
proposal is that altered MCU regulation and calcium signaling comprise a heretofore uncharacterized pathway
that regulates transcription in response to mitochondrial protein stress. Aim 1 will offer new insight about the
molecular mechanisms regulating the transcription, translation and protein stability of MCU. The functional
studies of Aim 2 will reveal how mitochondrial protein stress alters calcium signaling and transcription. Successful
completion of this proposal will advance the field by identifying novel players in the poorly understood
mitochondria-to-nuclear signaling pathway. These findings will also uncover a new function for mitochondrial
calcium signaling in the regulation of a transcriptional response central to the mitochondrial protein stress
response, and will reveal potential therapeutic targets for the treatment of neurodegenerative disease.
Completion of Aim 1 will provide valuable training in pairing gene editing with pharmacological tools to dissect
the function and regulation of MCU, a protein with great disease relevance. Completion of Aim 2 will provide
training in using laser-scanning confocal microscopy and live imaging techniques to study mitochondrial stress.
The University of Washington is very well funded and well equipped. Its top tier faculty, staff, and technicians,
and variety of state-of-the-art facilities will ensure the success of this proposed work.