Identification of direct targets of Bortezomib in Drosophila using a chemical proteomics approach
Author: Mengmeng Liu
Affiliation: Tulane University
Keywords: b. metabolism; b. metabolism
Identification of direct targets of Bortezomib in Drosophila using a chemical proteomics approach
Mengmeng Liu1, Yadagiri Kurra2, Rajitha-Udakara-Sampath Hemba-Waduge1, Xiao Li1,3, Wenshe Liu2, and Jun-yuan Ji*,1
1. Department of Biochemistry and Molecular Biology, Louisiana Cancer Research Center, 1700 Tulane Ave, New Orleans, LA 70112;
2. Department of Chemistry, Texas A&M University, College Station, TX 77843;
3. Current address: Department of Molecular Biology, Princeton University, Princeton, NJ 08544
*Email: ji@tulane.edu
Wnt signaling plays critical roles in regulating diverse biological processes, and deregulated Wnt signaling causes aberrant development and diseases such as cancer. We have previously reported that hyperactive Wnt signaling disrupts lipid homeostasis in Drosophila larvae, which can be strongly rescued by feeding the larvae with Bortezomib (BTZ) in an a-Catenin-dependent manner. BTZ is the first proteasome inhibitor approved by the Food and Drug Administration to treat patients suffered from multiple myeloma and mantle cell lymphoma. We have found that BTZ and two additional peptide boronic acids (PBAs), Delanzomib and Ixazomib, can rescue adipocyte defects caused by elevated Wnt signaling, but three other proteasome inhibitors that have different chemical structures (Carfilzomib, Marizomib, and Oprozomib) cannot rescue the phenotypes. These observations indicate that PBAs may have additional targets besides proteasome. To elucidate how PBAs regulates lipid homeostasis and Wnt signaling, we synthesized a photoactivatable biotin-tagged BTZ, which displays similar effects on rescuing adipocyte defects and inhibiting Wnt activity to BTZ. Using this biotin-tagged BTZ, we performed a pull-down assay using streptavidin beads followed by mass spectrometry analysis to identify proteins bind to BTZ. We have identified 126 candidate targets of BTZ, including majority subunits of the proteasome complex as expected. Interestingly, we also identified some peptidases and proteinases. We are performing genetic and cell biological analyses to determine whether these peptidases and proteinases play any roles in regulating a-Catenin stability and Wnt signaling in Drosophila. This study may advance our understanding of the molecular mechanism of how BTZ regulates a-Catenin stability and Wnt signaling in vivo.