James Chou, PhD
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical SchoolHMS Center for Molecular and Cellular Dynamics
NMR spectroscopy and membrane protein structure; viral ion channels; antiviral compounds
Apply advanced technologies to the reconstitution and structural biochemistry of membrane proteins, with a focus on viral ion channels; analyze the structure of membrane proteins at the level of atomic resolution, employing crystallization, x-ray diffraction, and NMR spectroscopy; span the
Influenza A, otherwise known as the common flu, is particularly dangerous for those with chronic illnesses, young children, and the elderly. The seasonal flu is linked to over 30,000 deaths in the US every year, and virulent strains of influenza A such as the H5N1 strain (i.e., the avian flu) threaten to cause severe outbreaks in the human population. Vaccination can be effective, but some segments of the population unable to mount an effective immune response (e.g., the elderly) may benefit from drug therapy. The M2 proton channel of the flu virus is indispensable for viral replication, explaining why it is one of only two viral molecules targeted by commercially available anti-flu drugs. However, the ability of the flu virus to mutate in order to “defend” against drugs such as amantadine has severely limited the use of the adamantane class of drugs. Only by understanding the high resolution structure-function relationships of the M2 channel, its interactions with drugs, and the etiology of drug resistance, can new rational and targeted drug development efforts be contemplated. Dr. Chou’s laboratory has enormous technological and theoretical capabilities that would be ideal for partnering with companies interested in rational drug design of a new generation of anti-flu therapeutics. Corporate funding would be instrumental in helping facilitate structural studies, in silico screening, and medicinal chemistry, all of which can be performed in this lab.
Current Research Interests
Employ purified preparations of reconstituted membrane proteins for NMR spectroscopic studies to obtain high resolution atomic structures of various membrane proteins, channels, and receptors, a group of molecules notoriously difficult to purify and characterize. In addition to the influenza M2 proton channel, the lab is also studying the cholesterol transporter and the mitochondrial uncoupling protein.
Using the structural information gathered from the NMR spectroscopy studies to infer function; thus, obtaining high resolution structural data is a very effective means for determining mechanistic aspects of membrane proteins.
Utilize DNA nanotechnology to assist directional orientation of proteins.
Dr. Chou’s laboratory has been interested in solving the structures of membrane proteins at a high resolution, employing NMR spectroscopy. Membrane proteins are notoriously difficult species to isolate and characterize, and the lab has developed an expertise in this area, such that structural characterization at an atomic resolution to be performed.
The lab has focused their recent studies on the M2 proton channel of the influenza A virus as well as larger helical membrane proteins such as the mitochondrial uncoupling proteins and the sarcoplasmic reticulum membrane protein phospholambam. The lab’s published findings pertaining to the M2 proton channel, an integral membrane protein, are considered a major advancement in understanding the mechanism of inhibition for the adamantane class of antiviral compounds, particularly since it is the first report that employs NMR spectroscopy to elucidate the structure of a proton channel. The lab unveiled the intricacies of the regulation that governs whether the proton channel is in the open or closed state. A so-called “tryptophan gate” was described that maintains the channel in a closed conformation. Upon exposure to a drop in pH, such as within the endosome environment, this gate is pried open, allowing protons to enter the viral interior. The acidification of the viral interior is a prerequisite for unraveling of the viral DNA and subsequent infection. The lab performed the NMR spectroscopic analysis on a complex of the M2 proton channel in association with the antiviral drug rimantadine (a structural analog of amantadine), and discovered that the drug “glues” the gate closed by binding on the outside of the proton channel, promoting the closed version of the gate. These findings should facilitate new approaches to circumvent influenza A resistance to drugs such as amantadine, now a serious worldwide issue.
Other previous studies form the lab have focused on phospholamban and the structural/functional consequences elicited by its phosphorylation, and the structural characterization of coiled-coil domains in proteins such as cGMP-dependent protein kinase Iα.