Research in the Michael Matunis Lab focuses on the SUMO family of small ubiquitin-related proteins. We study the covalent conjugation of SUMOs to other cellular proteins, which regulates numerous processes needed for cell growth and differentiation, and which, when defective, can lead to conditions such as cancer, neurodegenerative disease and diabetes.

Research in the Shigeki Watanabe Lab focuses on the cellular and molecular characterizations of rapid changes that occur during synaptic plasticity. Our team is working to determine the composition and distribution of proteins and lipids in the synapse as well as understand how the activity alters their distribution. Ultimately, we seek to discover how the misregulation of protein and lipid compositions lead to synaptic dysfunction. Our studies make use of cutting-edge electron microscopy techniques in combination with biochemical and molecular approaches.

Elevation of O-GlcNAc levels modulates numerous pathways in a manner consistent with increased cell survival, including the expression of heat shock proteins. The Zachara Lab's goal is to understand the O-GlcNAc regulated stress response, how this can be manipulated to improve patient outcome and how this response is misregulated in disease.

The Kalina Hristova Lab investigates the structure and assembly of biological membranes. Our team conducts research on the structural and thermodynamic principles that enable membrane protein folding and signal transduction across biological membranes. Part of our work has involved developing new tools to study the structure of thermally disordered fluid membranes and the energetics of biomolecular interactions in biological membranes. Through our studies, we have established a better understanding of the physical principles behind complex biological processes and the mechanisms of disease development in humans.

Research in the Wilson Lab focuses on three components of nuclear lamina structure: lamins, LEM-domain proteins (emerin), and BAF. These three proteins all bind each other directly, and are collectively required to organize and regulate chromatin, efficiently segregate chromosomes and rebuild nuclear structure after mitosis. Mutations in one or more of these proteins cause a variety of diseases including Emery-Dreifuss muscular dystrophy (EDMD), cardiomyopathy, lipodystrophy and diabetes, and accelerated aging. We are examining emerin's role in mechanotransduction, how emerin and lamin A are regulated, and whether misregulation contributes to disease.

Ion channels are pore-forming membrane proteins gating the flow of ions across the cell membrane. Among their many functions, ion channels regulate cell volume, control epithelial fluid secretion, and generate the electrical impulses in our brain. The Qiu Lab employs a multi-disciplinary approach including high-throughput functional genomics, electrophysiology, biochemistry, and mouse genetics to discover novel ion channels and to elucidate their role in health and disease.

The O’Rourke Lab uses an integrated approach to study the biophysics and physiology of cardiac cells in normal and diseased states. Research in our lab has incorporated mitochondrial energetics, Ca2+ dynamics, and electrophysiology to provide tools for studying how defective function of one component of the cell can lead to catastrophic effects on whole cell and whole organ function. By understanding the links between Ca2+, electrical excitability and energy production, we hope to understand the cellular basis of cardiac arrhythmias, ischemia-reperfusion injury, and sudden death. We use state-of-the-art techniques, including single-channel and whole-cell patch clamp, microfluorimetry, conventional and two-photon fluorescence imaging, and molecular biology to study the structure and function of single proteins to the intact muscle. Experimental results are compared with simulations of computational models in order to understand the findings in the context of the system as a whole. Ongoing studies in our lab are focused on identifying the specific molecular targets modified by oxidative or ischemic stress and how they affect mitochondrial and whole heart function. The motivation for all of the work is to understand • how the molecular details of the heart cell work together to maintain function and • how the synchronization of the parts can go wrong Rational strategies can then be devised to correct dysfunction during the progression of disease through a comprehensive understanding of basic mechanisms. Brian O’Rourke, PhD, is a professor in the Division of Cardiology and Vice Chair of Basic and Translational Research, Department of Medicine, at the Johns Hopkins University.

The Foster Lab uses the tools of protein biochemistry and proteomics to tackle fundamental problems in the fields of cardiac preconditioning and heart failure. Protein networks are perturbed in heart disease in a manner that correlates only weakly with changes in mRNA transcripts. Moreover, proteomic techniques afford the systematic assessment of post-translational modifications that regulate the activity of proteins responsible for every aspect of heart function from electrical excitation to contraction and metabolism. Understanding the status of protein networks in the diseased state is, therefore, key to discovering new therapies. D. Brian Foster, Ph.D., is an assistant professor of medicine in the division of cardiology, and serves as Director of the Laboratory of Cardiovascular Biochemistry at the Johns Hopkins University School of Medicine.

Intestinal chloride secretion is stimulated during diarrhea. Cholera toxin is secreted by bacterium Vibrio cholera and is responsible for the watery diarrhea after cholera infection. Mechanistically, cholera toxin increases intracellular cyclic AMP, which subsequently activates protein kinase A and the cystic fibrosis transmembrane regulator chloride channel (CFTR). However, we recently identified an intestinal cAMP-Ca cross-talk signaling pathway that is initiated by elevation of intracellular cAMP and subsequently elevates intracellular Ca concentrations through the exchange protein activated by cAMP (Epac). This observation suggests that both CFTR and calcium-activated chloride channels are targets of elevated intracellular cAMP signaling molecule. Therefore, we are studying the role of calcium-activated Cl channels in intestinal chloride secretion under physiological conditions and during diarrhea. We are also determining whether the recently identified transmembrane protein 16 family of proteins, which are calcium-activated chloride channels, is also involved in intestinal chloride secretion in addition to the well characterized CFTR channel. Increased understanding of regulation of intestinal Cl secretion provides the necessary background information for the development of therapeutic drugs for the treatment of diarrhea, constipation and cystic fibrosis. The discovery that calcium-activated chloride channels are involved in intestinal chloride secretion provides additional targets for anti-diarrhea drug development.

Secretory diarrhea is a leading cause of childhood morbidity and mortality in developing countries. While diarrhea can be treated with oral rehydration solution (ORS), inclusion of zinc with oral ORS has been shown to reduce the duration of diarrhea. However, how zinc improves diarrhea is not known. It has been shown that zinc acts as an intestinal epithelial cell basolateral potassium channel blocker of cyclic AMP-mediated chloride secretion. We discovered that zinc also stimulates intestinal sodium and water absorption via the epithelial Na/H exchanger, NHE3. Zinc reverses the effect of cyclic AMP inhibition of NHE3 activity. The effect of zinc on NHE3 cannot be duplicated with other divalent metal ions. It has been well established that Na/H exchanger regulatory proteins are involved in NHE3 regulation. Whether these regulatory proteins are involved in zinc stimulation of NHE3 is a focus of our study. Our goal is to reveal mechanisms to explain how zinc improves diarrhea and to understand the role of zinc in salt and water homeostasis in the gut. Our study will provide a scientific basis to justify the inclusion of zinc in ORS for the treatment of secretory diarrhea.