Functional Genomic Dissection of Human Mitochondrial Disorders 
Vamsi K. Mootha, M.D. Massachusetts General Hospital, Harvard Medical School, Broad Institute of MIT and Harvard

Mitochondria are tiny structures found in each of our body’s cells.  They are responsible for converting the food we eat into “cellular fuels” that can be used by our muscle, brain, heart, and other organs, to perform work.  Recent studies have shown that dysfunction of mitochondria can give rise to rare inherited disorders, as well as some very common human diseases, such as diabetes, neurodegeneration, and cancer.  With funding from the Charles E. Culpeper Scholarship, I plan to focus a portion of my lab’s efforts on a class of mitochondrial disorders that are characterized by devastating metabolic dysfunction, particularly in children.  At present, the diagnosis of these disorders is extremely difficult, and we have no therapeutic options for them.  Although these disorders are due to mutations in single genes, they give rise to a variety of symptoms – how lesions in individual genes can give rise to such a spectrum of clinical presentations remains a puzzle.  Using new tools that enable scientists to systematic disrupt individual genes my team will create cellular models of mitochondrial disease that we can then study in our laboratory.  In particular, we will use new technologies that enable us to monitor all the genes in the human genome and their response to these single genetic lesions.  Through the combined use of biochemistry, genetics, and mathematics, we then hope to identify the cellular pathways that go awry in these disease models, with the goal of identifying molecular targets against which rational therapies can be designed.

 The Role and Regulation of Autophagy in Epithelial Cell Homeostasis and Cancer 
Jayanta Debnath, MD, Assistant Professor of Pathology at the University of California San Francisco

Cancer is a deadly disease because an individual’s own cells develop genetic and biological changes allowing them to survive and grow in places where they do not belong. Extensive research has shown that one reason that cancer cells survive in unusual places is because they are protected from a process called programmed cell death, or apoptosis. Normally, apoptosis acts as a surveillance mechanism in the body that kills excess cells to prevent them from building up; this is not the case during cancer progression.

Although reduced apoptosis contributes to the ability cancer cells to survive, recent evidence is now indicating that other, less appreciated mechanisms, are also likely to regulate cancer progression. Without clarifying how such critical processes work, we are unlikely to develop effective treatments against cancer.

I recently found that when apoptosis is blocked, a second process, called autophagy, may act as a back-up mechanism to kill wayward tumor cells.  Autophagy is a widespread biological process in which a cell digests its own contents in response to various stresses.  When excessive autophagy occurs within a cell, it dies, because the cell literally “eats itself” to death. However, very little is known about the function or regulation of autophagy in human cells. My proposed studies intend to further explore the role of autophagy during cell death in both normal and cancer cells as well as determine how cancer genes and pathways regulate this poorly understood process.  These studies may provide novel information about the survival of cancer cells during cancer progression, and may enlighten the diagnosis and treatment of many different kinds of human cancer. 

Activating Apoptosis in Cancer Using Hydrocarbon-Stapled Helices  
Loren David Walensky, MD, PhD, Harvard Medical School and Attending Physician and Research Fellow in the Department of Pediatric Hematology/Oncology at the Dana-Farber Cancer Institute/Children’s Hospital Boston. 

Whether our cells will live or die, and whether we are therefore healthy or ill, is controlled by how proteins interact with each other inside our cells.  There are a huge number of proteins in our cells, and each one has a specific job to do.  Whether a protein can do its job depends on which other proteins are present inside the cell and what they are doing.  Think of a cell as the most complex assembly line in the world, and each protein as a worker on that assembly line.  How each protein gets its job done inside a cell depends on how it communicates with and interacts with the other proteins inside the cell.  Even a minor breakdown in communication between the proteins can have a dramatic effect on cells, and on our health.

There are certain proteins inside a cell called “BCL-2” proteins.  These proteins interact with one another to regulate whether a cell dies when it is old, diseased or no longer needed.  This cell death is called “apoptosis”.  Many human diseases directly results when apoptosis does not occur the way it should.  Premature cell death that reduces the number of healthy cells needed to continue important body functions can lead to illnesses like Alzheimer’s disease or stroke.  On the other hand, cancer occurs when diseased and damaged cells don’t die on time.  These and other diseases are the direct result of BCL-2 protein interactions that have gone awry.  Cures can come from fixing these BCL-2 protein problems.

BCL-2 proteins control cell death through small protein subunits called “peptides” that are helical, or spring-like, in shape.  Scientists can create other peptides that interact with these helical BCL-2 peptides to slow down or speed up cell death.  However, most current attempts to manufacture these artificial peptides have failed because the helical shape is so complex.  Peptides that have been manufactured in the right shape are so fragile that they break down before they can do their job.  Attempts to strengthen these fragile peptides have made it impossible for the peptides to get inside the cells to do their job. 

Dr. Walensky’s research focuses on developing and applying new approaches to this problem.  He will address two issues-using natural versus artificial peptides, and strengthening them without destroying their effectiveness.  Dr. Walensky will use a new process to chemically brace these natural peptides so that their shape, and therefore their curative activity, can be maintained.  He has used this chemical strategy, called “hydrocarbon-stapling”, to make a number of peptides with dramatically improved properties. 

Dr. Walensky has demonstrated that the stapled peptides are the right helical shape, are sturdy, and can enter and kill leukemia cells by turning on the BCL-2 death pathway.  When he administered these stapled peptides to mice with leukemia, the stapled peptide successfully blocked cancer growth and prolonged the lives of treated animals.  As a Culpeper awardee, Dr. Walensky’s future work will employ this new peptide-stapling strategy to produce a wide array of peptides that can interact with the BCL-2 pathway, in order to control cell death in a variety of human cancers.  The goal of Dr. Walensky’s research is to produce an arsenal of new compounds, a “peptide toolbox,” to block protein interactions that cause cancer, as illustrated by the anti-leukemia effect of his stapled BCL-2 peptide.