Kouacou Konan Assistant Professor of Biochemistry and Molecular Biology 308 Althouse Laboratory, University Park, PA 16802 Phone: (814) 863-8254 Fax: (814) 863-7024 E-mail: kvk10@psu.edu M.A. in Microbiology & Molecular Biology from Indiana University Ph.D. in Microbiology & Molecular Biology from Indiana University Postdoctoral, Stanford University of California Konan Lab Web Site

Hepatitis C and related viruses: replication complex formation and genome replication

Hepatitis C virus (HCV) is a positive strand RNA virus of the family Flaviviridae, including Dengue virus, West Nile virus, and bovine viral diarrhea virus. HCV is a leading cause of liver cancer worldwide. The long-term goal of this laboratory is to understand how HCV interaction with proteins results in pathogenesis and ultimately in liver cancer. Specifically, my lab is interested in understanding the role of nonstructural 4B protein, or NS4B, in HCV pathogenesis and biogenesis of liver cancer. Like many positive stranded RNA viruses, HCV replicates in the cytoplasm of infected cells, resulting in the formation of rearranged membranes called the membranous webs. The webs contain HCV nonstructural proteins (NS3, NS4A, NS4B, NS5A and NS5A) and viral RNA, suggesting that these novel membranes contain active HCV replication complex.

Role of NS4B protein in the recruitment of viral replication complex

One project in the lab seeks to understand how 1) all the viral proteins and 2) HCV RNA are assembled into the replication complex (Fig. 1). Expression of HCV NS4B protein alone induces the web structure but how all the replication complex is assembled into it still remains a mystery. For example, NS4A, NS5A and NS5B have membrane-anchoring domains, suggesting that they may not need NS4B to be recruited into the replication complex. On the other hand, NS3 protein is not a membrane-associated protein unless it is bound to NS4A and perhaps the other nonstructural proteins. It is therefore possible that the replication complex components are incorporated into the web structure in a random fashion. However, it is likely that NS4B and host factors play a key role in that process.

Structure-function analysis of HCV NS4B and associated host factors   

Another project focuses on uncovering all the possible functions associated with NS4B expression in the context of infectious virus. The molecular mechanism whereby NS4B induces the membranous webs still remains unknown nor do we know NS4B domains, NS4B residues as well as host partners crucial for forming this structure. For example, NS4B interacts with viral proteins, but we do not know how these interactions affect the function of NS4B and the other viral protein. Similarly, we do not know much about NS4B host partners and its interactions with these factors affect each other’s activity. We have shown that Rab5, an early endosome protein, co-localizes and interacts with NS4B protein and plays a role in HCV RNA synthesis. These findings are interesting given that most of HCV proteins are associated with the endoplasmic reticulum membranes. Studies are under way to understand the significance of Rab proteins in infectious HCV (Fig. 2) life cycle.

Examining whether NS4B function is conserved among flaviviruses

A third project in the lab relies on the use of bovine viral diarrhea virus (BVDV) as a model system to understand HCV replication complex formation. BVDV causes serious mucosal disease that is often fatal in infected cattle. Unlike HCV, BVDV is easier to propagate in cell culture; it can therefore provide a useful model for understanding HCV replication in infected cells. Very little is known about BVDV NS4B protein and whether this protein is key for the formation of BVDV replication complex. However, like HCV, BVDV NS4B protein is highly hydrophobic, with both the N-terminal and C-terminal domains predicted to be on the cytosolic side of the ER membrane. My lab is interested in defining the role of NS4B protein in BVDV replication, examining whether this function is conserved between HCV and BVDV and how this information can be used in the design of antivirals.

Representative Publications:

• Stone, M., S. Jia, W.D. Heo, T. Meyer, and K.V. Konan. 2007. Participation of Rab5, an early endosome protein, in hepatitis C virus RNA replication machinery. J. Virol. 81, 4551-4563.
• Konan, K.V., T.H. Giddings, Jr., M. Ikeda, K. Li, S.M. Lemon, and K. Kirkegaard. 2003. Nonstructural protein precursor NS4A/B from hepatitis C virus alters function and ultrastructure of host secretory apparatus. J. Virol. 77, 7843-7855.

Search the MEDLINE database at PubMed for articles by K Konan