PROTAC technology as a novel tool to identify the target of lathyrane diterpenoids

Proteolysis Targeting Chimera (PROTAC) is an emerging approach to selectively degrading target proteins by utilizing endogenous proteasome 1 .Since PROTACs can degrade target proteins without high affinity, it is natural to speculate that this technology can be used to identify the targets of natural products 2 .Although a recent study reported the employment of PROTACs to explore the unknown non-kinase target of a multi-kinase inhibitor sorafenib 2 , whether PROTACs can be used to find the potential targets of natural products remains unexplored.In previous study, we obtained several new lathyrane diterpenoids from Euphorbia lathyris and proved their potent antiinflammatory activity at low micromole levels with low toxicity 3 .Among them, (2S,3S,4S,5R,9S,11R,15R)-15-acetoxy-3cinnamoyloxy-5-hydroxyl-14-oxolathyra-6(17),12E-diene (ZCY-001) demonstrated the strongest activity against LPS-stimulated NO release with an IC 50 value of 3.0 Æ 1.1 mmol/L.However, the exact targets and the anti-inflammatory mechanism of lathyrane diterpenoids still need to be elucidated.V-maf musculoaponeurotic fibrosarcoma oncogene homolog F (MAFF) belongs to small MAFs family proteins (sMAFs), which also include MAFG and MAFK and are basic region leucine zipper (bZIP)-type transcription factors lacking transactivation domain 4 .sMAFs are indispensable partners required by CNC proteins including nuclear factor-erythroid 2-p45-related factor 2 (Nrf2) to positive-transcriptionally activate target genes involved in antioxidative response, while homodimers of sMAFs repress this activation by competitively binding with MARE or ARE 4 .Herein, lathyrol, with the core scaffold structure of the most active lathyrane diterpenoid ZCY-001 from E. lathyris, was selected to synthesize a PROTAC molecule (ZCY-PROTAC) to identify the targets of lathyrane diterpenoids.We identified MAFF as the target of lathyrol and (2S,3S,4R,5R,7R,9S,11R,15R)-5,15diacetoxy-3-benzoyloxy-7-hydroxyl-14-oxolathyra-6(17),12Ediene, ZCY020, a similar lathyrane diterpenoids.The findings imply that PROTAC technology was a promising new method for the target identification of natural products.