Discovery of pH-Selective Marine and Plant Natural Product Inhibitors of Cathepsin B Revealed by Screening at Acidic and Neutral pH Conditions

Abstract

Dysregulation of cathepsin B, which involves the translocation of the enzyme from acidic pH lysosomes to the neutral pH cytosol, followed by the initiation of cell death and inflammation, occurs in numerous brain disorders. The wide difference in the acidic pH (4.6) of lysosomes compared to the neutral pH (7.2) of the cytosol suggests that screening at different pH conditions may identify pH-selective modulators of cathepsin B. Therefore, a collection of pure marine and plant natural product (NP) compounds, with synthetic compounds, was screened at pH 4.6 and pH 7.2 in cathepsin B assays, which led to the identification of GER-12 (Crossbyanol B) and GER-24 ((7 Z ,9 Z ,12 Z )-octadeca-7,9,12-trien-5-ynoic acid) marine NP inhibitors at acidic pH but not at neutral pH. GER-12 was effective for the reversible inhibition of cathepsin B, with an IC 50 of 3 μM. GER-24 had an IC 50 of 16 μM and was found to be an irreversible inhibitor. These results show that NP screening at distinct biological pH conditions can lead to the identification of pH-selective cathepsin B modulators. These findings suggest that screening efforts for molecular probes and drug discovery may consider the biological pH environment of the target in the disease process.

Light-gated Integrator for Highlighting Kinase Activity in Living Cells

“…Among these, we took particular note of four interesting compounds that suggest the modulation of PKA activity by certain key pathways. For instance, Psammaplin A, derived from a marine sponge, inhibits class I histone deacetylase (HDAC1) 19 ; Kalkitoxin induces cellular hypoxia by inhibiting the electron transport chain (ETC) complex 1 20 ; and Crossbyanol B and (7Z,9Z,12Z)- octadeca-7,9,12-trien-5-ynoic acid were reported as inhibitors of Cathepsin B 21 . We verified these compounds using real-time imaging in HEK293T cells expressing a sensitive PKA activity biosensor, AKAR3ev 22 , and indeed observed definite bioactivities toward PKA within 20 min of drug addition (Supplementary Fig.…”

Antibacterial activity and bioactive compounds of a marine macroalgae endophytic fungi, Hypoxylon monticulosum

“…S-4-benzyl-3-((S)-3-hydroxy-2,2dimethyloct-7-ynoyl)-5, 5 dimethyloxazolidin-2-one and R-4-benzyl-3-((R)-3-hydroxy2,2-dimethyloctanoyl) 5,5 dimethyloxazolidin-2-one, are marine and natural product inhibitor compounds of cathepsin B which is a cysteine protease that can cause brain disorders (Phan et al, 2022).…”