Fei Hong, PhD
Postdoctoral Associate
The Genomics Institute of the Novartis Reserch Foundation, San Diego, CA
PhD (2005)
Advisor: Dr. Daniel Liebler
While at the University of Arizona, my project was to use mass spectrometry to analyze the mechanism of activation of Keap-Nrf2 singaling pathway induced by electrophiles. Nrf2 is the transcription factor that regulates the expression of Phase II enzymes so that cells can defend themselves against electrophiles. Keap1 binds to Nrf2 as adaptor protein for the ubiquitination and degradation of Nrf2. when electrophilic inducer bound to specific cystein residues of Keap1, Nrf2 is stabilized and activated. With some biotin-taged electrophiles and mass spectrometry, we mapped the adduct sites formed on keap1. we found when electrophiles attack the central linker domain of keap1, ubiquitination is transferred from Nrf2 to keap1 so that nrf2 is stabilized and activated.
In addition, we studied a cancer chemopreventive agent sulforaphane, which is isolated from cruciferous vegetables, such as broccoli and cauliflower. We found sulforaphane can also form adduct on Keap1 and activate Nrf2, but using a different mechanism. Since sulforaphane adducts on cysteine residue are labile and with standart sample preparation procedure, not adduct can be mapped with mass spectrometry. We worked on the methodology and finally we come up with a new protocol to characterize labile adducts.
I am currently postdoctoral associate at GNF doing protein profiling using mass spectrometry. I primarily work on two projects. One is to develop a new method to isolate N-terminal peptides from internal and C-terminal peptides in a protein complex so that more proteins in the complex can be identified. This new method utilizes fluorous affinity column to separate acetylated N-terminal peptides from fluorous tagged internal and C-terminal peptides which have a high affinity to fluorous silica gel. The other project is to identify substrate profiles of a given protease MTSP1 in vivo by utilizing the new method we developed. The profiles of N-terminal peptides are different in untreated cells and in the cells that MTSP1 activity is inhibited. By identifying the new generated N-terminal peptides, MTSP1 substrates could be identified.