Lab Research Focus
Infectious diseases are identified as the third major cause of death in the United States. Development of effective and economic therapy of infectious diseases requires thorough understanding of the biology of these infectious agents and innovative approaches to the problems. My laboratory has been involved in X-ray crystallographic analysis of critical proteins and design of novel drugs based on the protein structure.
Influenza virus neuraminidase - Influenza virus remains to be a major causative agent for a large number of death among elderly people and young children, and huge economic losses due to illness. Influenza virus is an enveloped virus containing negative strand segmented genomic RNA's. On the viral membrane surface, there are two major antigens, haemagglutinin and neuraminidase. We have been working on the three-dimensional structure of neuraminidase, a tetrameric glycoprotein of 240,000 daltons. Based on the structural information, we started to design new inhibitors which should have a potential to be developed as antiviral drugs. The process of inhibitor design involves modeling potential inhibitors using the active site structure and several computer programs; chemical synthesis of the designed inhibitors and testing these inhibitors for their efficacy; and determining the complex structure of new inhibitors and neuraminidase, which could suggest further modifications of the inhibitors. Today, a new series of inhibitors with a good inhibitory effect (best IC50<5x10-8m) has been designed and a patent application has been approved for these compounds. A novel pattern of interactions between NA and inhibitors was identified. This is the first time a noncarbohydrate inhibitor was ever designed to fit the active site of NA. The best compound was shown to inhibit influenza virus replication in cell culture and a mouse model system. we also expand the scope of drug design to include bacterial sialidases which are important virulent factors of bacterial pathogenesis. For instance, data showed that elevated sialidase activity in bacterial vaginosis patients is correlated to prematurity in pregnant women. Bacterial sialidase also plays a significant role in the unusual colonization of pseudomonas aeruginosa in cystic fibrosis patients. We suggest that inhibitors of bacterial sialidases can be used as prophylactic drugs to prevent bacterial infections in these critical cases. The structure of two bacterial sialidases has been determined and made available. We have designed and synthesized two inhibitors based on these structures. We should be able to further improve these inhibitors and test them for antimicrobial activities in vivo. Crystals of salmonella sialidase have been reproduced in my laboratory and are used for studying the inhibitor-enzyme complexes. The sialidase inhibitors can also be used to prevent trypanosome cruzi infection, the causative agent of chagas' disease because a trans-sialidase of t. cruzi, a very similar enzyme to bacterial sialidase, may also be inhibited by these inhibitors.
Recently, we successfully solved the structure of the matrix protein M1 of influenza virus to 2.2 Å resolution. M1 is involved in transport and assembly of viral genomic RNA. The structure revealed the regions which mediate the interaction between the viral membrane and the RNA nucleocapsid. This will provide a new target for design of anti-influenza virus drugs. Other influenza proteins are also under study.
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