Clomipramine Hydrochloride

Clomipramine hydrochloride was identified as an irreversible inhibitor of the HECT-type ubiquitin ligase ITCH through high-throughput screening of a chemical library. Biochemical assays demonstrated that clomipramine blocked ITCH auto-ubiquitylation activity in an irreversible manner, as ubiquitylation activity remained absent after dialysis of clomipramine-pretreated ITCH samples. Clomipramine also inhibited other HECT E3 ligases but not RING E3 ligases, suggesting a HECT-domain-specific mechanism.
Structural analogs of clomipramine revealed that the chloride group on the aromatic moiety and the length of the side chain are critical for ITCH inhibitory activity. Docking studies showed that clomipramine may bind between the N- and C-lobes of the ITCH HECT domain or interact directly with the catalytic cysteine residue. The compound also blocked autophagic flux and synergized with chemotherapeutics to inhibit cancer cell growth.

Fig. 1 Schematic representation of the layout of the ELISA assay used for the HTS. (Amelio I.; et al. 2014)