James M. Hogle, Ph.D.

Our laboratory uses structural approaches to explore how viruses enter cells and replicate.

Research:

Our laboratory uses structural approaches to explore how viruses enter cells and replicate. Current research in the laboratory is focused in two areas: 1) a multiscaled approach to characterizing the cell entry pathway of poliovirus and other simple nonenveloped viruses, 2) structural studies of key proteins in the replication of herpes viruses (in collaboration with Don Coen).

Membrane fusion provides a conceptually simple mechanism for enveloped viruses to deliver their genomes into the cytoplasm of target cells. In contrast, viruses which lack an outer membrane must provide a mechanism that allows a large nucleocapsid, or at the very least the viral genome, to cross a membrane in order to gain access to the interior of the cell. This process remains poorly understood. We are taking a combined structural approach to characterize the cell entry pathway of poliovirus as a simple model for studying nonenveloped virus entry. The combined approach uses cryoelectron microscopy to characterize soluble forms of cell entry intermediates at high resolution, and cryoelectron microscopy and cryoelectron tomography to characterize membrane-associated intermediates at intermediate resolutions, using a receptor-decorated liposome model developed in the lab.  Our cryoEM studies have benefitted greatly from the rapid advances in instrumentation and image processing in the field, and have reached a point were near-atomic resolution of well-behaved samples is becoming routine.   The structures to date have resulted in a number of surprises including the demonstration that viral peptides that are externalized and insert into membranes during infection and the viral genome are released from a site midway between a particle twofold axis and a particle fivefold axis not at the fivefold axis as previous models had proposed, and a clear demonstration that the viral RNA is released across intact membranes through a rather long tube and a pore created by the externalized viral peptides.  We are using the receptor-decorated liposome model to characterize the kinetics of RNA translocation into tethered liposomes on at the single particle level, and a combination of cross-linking and limited proteolysis to characterize the components of the tube and the pore.