Project Summary/Abstract
Loss of mitochondrial homeostasis significantly decreases cellular health and causes many age-based and
metabolic diseases. Cells are equipped with a number of pathways that remodel mitochondrial during stress.
Mitochondrial-Derived Compartment (MDC) formation is a recently discovered mitochondrial remodeling
mechanism that is activated in response to many metabolic stresses in both yeast and mammals. MDC structures
are large (1µm diameter) multi-bilayer structures that are generated from the mitochondrial outer membrane and
selectively sort mitochondrial proteins for degradation. Following their formation, MDCs are broken down by
mitochondrial fission and targeted to the vacuole through bulk autophagy pathways. MDCs form in response to
amino acid-associated stresses such as cellular aging, translation inhibition, vacuolar/lysosomal deacidification,
and Target of Rapamycin (TOR) inhibition. However, it remains unclear what the function of MDCs is within cells
and how these structures promote mitochondrial adaptation.
In addition to amino acid stress, I recently found that acute glucose starvation is a novel and potent
inducer for MDC formation in S. cerevisiae. This proposal will characterize the mechanism of glucose starvation-
induced MDC formation and determine how their formation facilitates mitochondrial adaptation during a transition
from fermentative to respiratory metabolism. Preliminary studies have shown that glucose starvation-induced
MDCs are not dependent on amino acid availability, and these MDC structures are also delivered to the vacuole
through autophagy. Also, a change from fermentative to a non-fermentable carbon source triggers MDC
formation. The scope of metabolic perturbations that activate the MDC pathway appears far more generalized
to many components of central metabolism. I hypothesize that glucose starvation induces MDC formation
by altering the TCA cycle or mitochondrial energy constituents (ATP, NADH) paired with the activation
of nutrient signaling pathways. Additionally, given the conditions in which MDCs form, I hypothesize
that this pathway is critical for the transition of mitochondria from a fermentation state to an elevated
oxidative phosphorylation metabolism. These hypotheses will be tested in two aims, which will 1) determine
the mechanism by which acute glucose depletion or carbon source switching activates MDC formation, and 2)
test the requirement of MDC formation in maintaining viability and promoting metabolic adaptation during carbon
source transitions. This innovative study will expand the mechanistic understanding of the MDC pathway as a
remodeling mechanism that is significant to many metabolic transitions. In addition, the completion of these
studies and career development activities outlined in the application will provide me with the necessary training
to complete my graduate studies and transition to the next stage of my research career.