The research in my lab focuses on elucidating the structural basis of innate immune responses towards microbial nucleic acids. The cGAS/STING pathway plays a central role in innate immunity toward bacterial and viral DNA. cGAS is activated by dsDNA and catalyzes the synthesis of a cyclic dinucleotide cGAMP, which binds to the adaptor STING that mediates the recruitment and activation of protein kinase TBK1 and transcription factor IRF-3. Activated IRF-3 translocates to the nucleus and induces the expression of type I interferons (IFN), an important family of antiviral cytokine. To elucidate the mechanism of cGAS activation, we determined the structures of cGAS in isolation and in complex with DNA. The cGAS/DNA complex structure reveals that cGAS interacts with DNA through two binding sites. Enzyme assays and IFN-? reporter assays of cGAS mutants demonstrate that interactions at both DNA binding sites are essential for cGAS activation. To investigate how cGAMP activates STING, we determined the structures of STING in isolation and in complex with cGAMP. These structures reveal that STING forms a V-shaped dimer and binds cGAMP at the dimer interface. We have also determined the structures of TBK1 in complex with two inhibitors, which show that TBK1 exhibits an I?B kinase fold with distinct domain arrangement. To elucidate the mechanism of IRF-3 recruitment by STING, we determined the structure of a phosphorylated STING peptide bound to IRF-3. To understand how phosphorylation activates IRF-3, we solved the structure of an IRF-3 phosphomimetic mutant bound to CBP, which reveals how phosphorylation induces the dimerization and activation of IRF-3.
- Li, W., Wang, H., Chen, Z., Ye, Q., Tian, Y., Xu, X., ... Tan, X. (2014). Probing the metal specificity mechanism of superoxide dismutase from human pathogen Clostridium difficile. Chemical Communications. 50(5), 584-586.
- Li, X., Shu, C., Yi, G., Chaton, C. T., Shelton, C. L., Diao, J., ... Li, P. (2013). Cyclic GMP-AMP Synthase Is Activated by Double-Stranded DNA-Induced Oligomerization. IMMUNITY. 39(6), 1019-1031.
- Morales, K. A., Yang, Y., Long, Z., Li, P., Tayo, A. B., Hart, P. J., & Igumenova, T. I. (2013). Cd2+ as a Ca2+ Surrogate in Protein-Membrane Interactions: Isostructural but Not Isofunctional. Journal of the American Chemical Society. 135(35), 12980-12983.
- Shu, C., Sankaran, B., Chaton, C. T., Herr, A. B., Mishra, A., Peng, J., & Li, P. (2013). Structural insights into the functions of TBK1 in innate antimicrobial immunity.. Structure. 21(7), 1137-1148.
- Yi, G., Brendel, V. P., Shu, C., Li, P., Palanathan, S., & Kao, C. C. (2013). Single Nucleotide Polymorphisms of Human STING Can Affect Innate Immune Response to Cyclic Dinucleotides. PLoS ONE. 8(10), e77846-e77846.
- Watts, Tylan Aubrey (2013-08). Mechanism of MDA5 Recognition of Short RNA Ligands and Crystal Structure of PepQ. (Master's Thesis)
- Sung, Min Woo 1980- (2012-12). Mechanisms of Microbial DNA Sensing by the AIM2 Inflammasome and Structural Study of Polynucleotydyl Transferase1 (pnt1) from Arabidopsis Thaliana. (Master's Thesis)
- Lu, Cheng (2012-08). Structural Basis of Viral RNA Recognition by RIG-I-Like Receptors. (Doctoral Dissertation)
- Kuo, Nai-Wei (2011-05). KaiC CII Ring Flexibility Governs the Rhythm of the Circadian Clock of Cyanobacteria. (Doctoral Dissertation)
- Kim, Yong-Ick (2008-12). The day/night switch of the circadian clock of synechococcus elongatus and hydrogen bonds of dna and rna. (Doctoral Dissertation)