In the Jiang Lab, we are interested in technology development and applications of cryo-electron microscopy (cryo-EM) imaging and 3-D reconstruction of viruses and macromolecular complexes, nanobiology, diseases, and drug discovery. We aim to broaden the applicability of high resolution (2-4 Å) cryo-EM to targets of low abundance or high level of dynamics, and novice users. The efforts on the applications and method developments drive each other reciprocally. We particularly enjoy collaborating with colleagues on systems with biological significance, which often face technical challenges and require new method developments.
Atomic models of human Tau filaments and development of Tau ligands
Specific protein inclusions define most neurodegenerative diseases at the pathological level. The conversion of soluble to insoluble filamentous tau protein is central to many human neurodegenerative diseases such as Alzheimer disease (AD). In AD, all six isoforms of tau are present in the disease filaments as either paired helical (PFH) or straight (SF), with both types of filaments sharing a common structural subunit. Interestingly, the morphologies of tau filaments in different diseases may vary, even when they are made of the same isoforms. Together with our collaborators, we will elucidate the structural basis and pathological mechanisms implicated in sporadic, hereditary and secondary tauopathies by determining the structure of tau filaments from the brain tissues of patients by cryo-EM and to identify specific ligands for the tau filaments that could be used for in vivo imaging.
Structural basis of Norovirus assembly and host cell entry
Human noroviruses (HuNoVs) are the major cause of nonbacterial gastroenteritis worldwide. Despite the serious public health concern, knowledge about the infection mechanism and pathogenesis of HuNoVs is limited and there is no vaccine or antiviral. Together with our collaborators, we have established the primate Tulane virus (TV) as a model system for HuNoVs studies. We will use TV and HuNoV VLPs to understand the structural basis of viral particle assembly and the interactions between HuNoVs and their cellular receptors in the attachment/penetration into host cells and the conformational dynamics of the viral capsid and genome release in the early stage of viral infection. We also aim to develop the TV system into a surrogate for antiviral screening/evaluation. We will use cryo-EM to determine near-atomic resolution (2-4 Å) structure of TV, the dynamic conformations accompanying receptor binding and genome release, and its complex with antiviral lead compounds.
Bacteriophage structures and applications
By understanding the phage structure, from host-attachment to virion assembly, we can better understand how structure influences function. Phages are the most abundant life form on the planet, and we know surprisingly little about phage diversity. Together with our collaborators, we are studying the infection process and using cryo-EM to determine the structure of large, tailed phages. We are also interested in developing phage capsids as drug delivery vehicles.
Affinity Cryo-EM: is it too crazy to dream for single-cell structural biology?
We have previously developed cryo-EM grids with on-grid affinity binding capability (such as Ni-NTA, antibodies, and covalent conjugation) to overcome low yield and short-lived unstable sample problems. We are refining the method to demonstrate 2-4 Å resolution capability of affinity grid method for smaller, lower symmetry protein complexes not only for purified, low concentration samples but also for direct capture of target samples from cell lysate or virus particles from patient samples for native state structures. We are also interested in applying affinity cryo-EM to study drug-target complexes in cell lysate to extend structural based drug design from chemical buffer environment to native cellular environment aiming at more relevant structural information and improved success rate of drug discovery.
CryoVR: virtual reality augmented hands-on training for cryo-EM
TEM instrument is a complex machine that still requires tedious manual operations and the learning curve is steep. Together with collaborators, we are developing virtual reality-augmented training system (CryoVR) to allow new users to learn/practice at their own pace and quickly master the operation skills without the fear of breaking the expensive machines or being delayed by the limited availability of trainers and instruments. The CryoVR-training system will help reduce accidental breaking of the expensive microscopes and sample preparation instruments by novice users, reduce downtimes, and maximize the service capacity of the instruments.