Core Research Projects
More Than a Platitude – That Which Does Not Kill Us Makes Us Stronger
Determining the Identity of MitoKATP: A Key Player in Cardioprotective Preconditioning.
In a laboratory setting, one can coax a heart to be more resistant to a heart attack caused by long periods without blood flow. Ironically, this is actually done by interrupting blood flow to the heart a few times, for short periods, before the onset the heart attack. The process is called ischemic preconditioning (IPC), and understanding it, in the hopes of harnessing this protective response, has been a high priority for cardiovascular scientists for nearly 25 years. Work by other labs in the mid-90s showed that the effects of IPC could be mimicked pharmacologically with potassium channel opening (KCO) drugs. Potassium channels (K+-channels) are the proteins that allow K+ across the biological membranes of cells and one class of these channels is sensitive to ATP (KATP). Specifically, it was shown that the KCOs conferred protection by acting preferentially on KATP channels resident in mitochondria. Identifying the specific gene-products that comprise this MitoKATP channel has been viewed as one of the Holy Grails of preconditioning research for nearly 20 years.
Recently, we have identified an inward rectifying potassium channel in bovine mitochondrial inner membranes, by mass spectrometry, called ROMK, and confirmed it was indeed part of the long-sought mitoKATP channel. Though we think this represents a great step toward a better understanding of preconditioning, it is, however, only the first step in resolving the identity of mitoKATP, since mitoROMK surely possesses an ancillary regulatory subunit that modulates its activity. We are now focused on identifying and validating mitoROMK-binding partners and post-translational modification of mitoROMK. Defining both subunits of MitoKATP will be essential to resolve existing controversies in the literature and test proposed models and mechanisms by which mitoKATP mediates cardioprotection. Moreover, discovery of MitoROMK binding partners will enable us to refine the design of high throughput cell-based strategies for therapeutic drug discovery.
This project is funded by a National Scientist Development Grant (12SDG12060056) from the American Heart Association (PI: Dr. Brian Foster).
Signaling Networks that Underlie Genetic Cardiomyopathies: Insights from a Fly on the Wall
In collaboration with Dr. Anthony Cammarato, Ph.D.
Sudden death associated with mutations of proteins involved in contraction of the heart is one the leading causes of death among young and middle-aged males, a fact engrained in the public consciousness by media coverage of the untimely deaths of promising college athletes. Since the landmark studies documenting the genetic basis of familial hypertrophic cardiomyopathy, over 900 mutations of the cardiac sarcomeres have been implicated in both hypertrophic and dilated cardiomyopathy. Indeed, as high-throughput gene sequencing gains traction, the rate of discovery of new mutations will undoubtedly increase in the future. To make matters worse, the pathophysiology is extremely complex, as are molecular mechanisms that underlie it. Tackling this kind of complexity systematically demands new tools and models systems.
My lab is working with Dr. Anthony Cammarato, who has spearheaded the use of the fruit fly, Drosophila melanogaster, as a model for the study of the sarcomeric cardiomyopathies. In a recent breakthrough study, we have succeeded in using proteomic techniques to compile a protein compendium of the Drosophila cardiac tube. Now we are using quantitative proteomic approaches to see how cardiomyopathy perturbs protein networks. By determining the impact of a single gene mutation on protein signatures of the cardiac myocyte, our goal is to streamline the search for genetic suppressors of restrictive and dilated cardiomyopathy.
This project is funded by an R21 Exploratory/Development Grant (R21HL108052) from National Heart Lung and Blood Institute of the National Institutes of Health (PI: Dr. Brian Foster, Co-PI: Dr. Brian O’Rourke, Co-invest: Dr Anthony Cammarato).
Signaling Networks in Heart Failure Progression: Can a New Model Help Bridge the Translation Gap?
In collaboration with Dr. Brian O’Rourke, Ph.D.
Despite the pace with which we discover new mechanisms that underlie heart failure (HF) in existing animal models, remarkably few of these insights ultimately lead to new drugs for the treatment of patients. Many promising candidate therapies just don’t survive the many rigorous tests necessary to ensure drug efficacy and patient safety. The gap between basic science discovery and bringing a treatment to market is known in the pharmaceutical industry as the Valley of Death. How then, do you we bridge that gap? One way, perhaps, is to come up with new models that more closely mimic human physiology. My collaborators, Dr Brian O’Rourke & Dr. Ting Liu, have recently made great strides in this area by developing a new animal model of HF that recreates the kind of structural remodeling seen in the progression of human disease. Moreover, it is one of few models which demonstrate sudden cardiac death (SCD) caused by misfiring of the electrical circuits that initiate the heartbeat. This is important because SCD is a leading cause of death in patients within the first 5 years after a diagnosis with HF.
Our collaboration with Dr. O’Rourke and Dr. Liu seeks to understand how protein networks are perturbed in this new exciting HF model. Using proteomics, we can also look at more than simple protein levels, but also look at a range of post-translational modifications (PTMs; e.g. phosphorylation, acetylation, etc.) that may modulate protein activity. Examining crosstalk between protein and PTM networks may hold the key to finding new pathways that can be targeted therapeutically.
Funded by the Johns Hopkins Center for Innovation in Heart Failure/NHLBI contract HHSN268201000032C
(Center PI: Dr. Jennifer Van Eyk, Project PI: Dr. Brian O’Rourke)
My lab maintains a strong interest, and active fruitful collaborations, in the field of cardiac myofilament structure/function and how it is perturbed in heart disease ranging from myocardial stunning to hypertrophic cardiomyopathy and heart failure. Collaborators include Dr. Anne Murphy, Dr. Jolanda van der Velden, Dr. Ger Stienen, Dr. William Lehman and Dr. Anthony Cammarato.