A new quinoline-based chemical probe inhibits the autophagy-related cysteine protease ATG4B

The cysteine protease ATG4B is a key component of the autophagy machinery, acting to proteolytically prime and recycle its substrate MAP1LC3B. The roles of ATG4B in cancer and other diseases appear to be context dependent but are still not well understood. To help further explore ATG4B functions and potential therapeutic applications, we employed a chemical biology approach to identify ATG4B inhibitors. Here, we describe the discovery of 4-28, a styrylquinoline identified by a combined computational modeling, in silico screening, high content cell-based screening and biochemical assay approach. A structure-activity relationship study led to the development of a more stable and potent compound LV-320. We demonstrated that LV-320 inhibits ATG4B enzymatic activity, blocks autophagic flux in cells, and is stable, non-toxic and active in vivo. These findings suggest that LV-320 will serve as a relevant chemical tool to study the various roles of ATG4B in cancer and other contexts.

In vitro studies of the activity of newly sinthesized nociceptin / orphanin FQ receptor ligand analogues

Based on template hexapeptides Ac-Arg-Tyr-Tyr-Arg-Trp-Lys-NH(2) and Ac-Arg-Tyr-Tyr-Arg-Ile-Lys-NH(2) analogues and corresponding deacylated homologues were synthesized substituting ornithine, diaminobutanoic (Dab) and diaminopropanoic (Dap) acids for lysine at position 6. The aim was to investigate the effect of the newly synthesized compounds on the neurogenic contractions of isolated rat vas deferens. Ac-Arg-Tyr-Tyr-Arg-Trp-Lys-NH(2) and its analogues manifested a strong inhibitory effect on the neurogenic contractions without effect on the muscle tone, which is characteristic effect of NOP receptor agonists. In contrast, Ac-Arg-Tyr-Tyr-Arg-Ile-Lys-NH(2) and its analogs manifested a strong inhibitory effect on the muscle tone and negligible effect on the neurogenic contractions which is characteristic effect of NOP receptor antagonists. The most active were the peptides in which Dab or Dap is the substitute. The study reveals that substitution of Lys with shorter amino acids could increase agonist or antagonist activity of the peptide.