PROJECT SUMMARY
Mitochondria are organelles that play a dominant role in energy metabolism and many other cellular
processes. Mitochondrial dysfunction is associated with primary heritable diseases and aging-related declines
in health, including chronic pathologies like cancer, diabetes and neurodegeneration. There are currently no
cures for mitochondrial diseases. However, Szeto-Schiller (SS) peptides have emerged among the most
promising therapeutics for promoting mitochondrial health. As shown by preclinical and clinical trials, and as
exemplified by the lead compound SS-31 (Elamipretide), SS peptides show exceptionally broad therapeutic
efficacy in treating mitochondrial dysfunction. Using a multidisciplinary approach, our research team has
conducted the first in-depth analysis of the molecular mechanism of action (MoA) of SS peptides. Our work
supports a unique mechanism in which SS peptides interact with cardiolipin-rich mitochondrial membranes and
modulate general physical membrane properties, thereby underpinning their broad therapeutic potential. The
objective of the proposed project is twofold. The first goal is to thoroughly understand the MoA of SS peptides.
To this end, we will leverage our solid foundation of mechanistic insights to test, refine, and expand our
working models using computational, reductionist, mitochondrial, and cellular systems. The second goal is to
identify the physicochemical properties of SS peptides that are most critical to their mechanism. To this end,
we will evaluate a series of rationally designed SS peptide constructs with variations in the tetrapeptide
cationic/aromatic motif, using our established functional assays. With our highly interdisciplinary research
team, we will approach these goals as three separate aims. First, we will address how SS peptides interact
with lipid bilayers and modulate their physical properties using a combination of computational and biophysical
approaches with biomimetic model membrane systems. This will render critical information on equilibrium
peptide binding models, high resolution structural information on peptide conformational dynamics and
interaction with lipid groups, and how peptides modulate membrane electrostatics, lipid structural dynamics,
and bilayer polymorphic changes. Second, we will evaluate the effects of SS peptides on the structure and
function of membranes from yeast and mammalian models. This will establish the sites of peptide interaction in
the morphologically complex mitochondrion, how peptides affect the stability and assembly of membrane
complexes, the distribution of lipids within mitochondria, and lipid turnover kinetics. Finally, using mitochondrial
and cellular models, we will analyze the mechanisms by which SS peptides restore function under pathological
conditions including oxidative stress, high calcium load, and amyloidogenic proteins involved in type II diabetes
and Alzheimer’s disease. By this multi-tiered approach, our results will yield unprecedented insights into the
mechanism of this class of therapeutics with particular relevance to aging-related diseases. Further, our
peptide screen will inform the design of SS peptide variants with greater efficacy and/or bioavailability.
