Structural Analysis of Phenothiazine Derivatives as Allosteric Inhibitors of the MALT1 Paracaspase

Abstract

Second site: In the crystal structure of human MALT1casp‐Ig3 (mucosa‐associated lymphoid tissue lymphoma translocation protein 1) in complex with the tricyclic phenothiazine derivative thioridazine (violet in the picture), the inhibitor is bound in a hydrophobic pocket far from the active site. This explains the action of phenothiazine derivatives as noncompetitive, reversible inhibitors.

Lymphocyte signaling and activation by the CARMA1-BCL10-MALT1 signalosome

“…Second, substrate binding induces structural rearrangements that release the paracaspase from auto-inhibition (Wiesmann et al, 2012). The two-step activation model was confirmed by the identification of allosteric small molecule MALT1 inhibitors, which prevent the conformational rearrangement required for activation by binding to a hydrophobic pocket formed at the interface of the paracaspase and Ig3 domains ( Schlauderer et al, 2013). The critical role of the Ig3 domain for cellular MALT1 activation is also supported by the finding that mono-ubiquitination at Lys644 is inducing MALT1 proteolytic activity upon T cell stimulation (Pelzer et al, 2013).…”

“…MI-2 was suggested to irreversibly bind to the active site of MALT1, but recent data indicate that the compound is not specifically targeting the catalytic center of MALT1 (Xin et al, 2016). Mepazine and Thioridazine act as noncompetitive, reversible inhibitors by attaching to an allosteric binding site between the paracaspase and the Ig3 domain preventing the conformational changes needed for MALT1 activation (Schlauderer et al, 2013). Interestingly, treatment of mice with the phenothiazine mepazine attenuates induction and progression of EAE supporting the clinical use of MALT1 inhibitors for the treatment of autoimmune diseases (McGuire et al, 2014).…”

Development of new Malt1 inhibitors and probes

“…With these three compounds, assays were carried out at lower concentrations in three independent experiments ( Figure 5). The results reveal that those inhibitors containing a parasubstituted benzyl group (9,11,13,15,17,19) show much more potent inhibitory activities against Malt1 than the corresponding meta-substituted analogs (10,12,14,16,18,20). As well, three para-substituted benzyl derivatives (9,11,19) show more potent inhibitory activities against Malt1 than the corresponding 3,4-disubstituted derivatives 22,24).…”

“…Structure elucidation of Malt1 crystals complexed to mepazine reveals binding of 2 to an allosteric site at the interface between the catalytic domain and the Ig3 domain. 10 Occupation of this allosteric site is thought to prevent rearrangement of the inactive enzyme into the active conformation. MI-2 ( Figure 1A, 3) 9b was identified to be a covalent and irreversible inhibitor of the Malt1 protease activity.…”

Synthesis and SAR evaluation of novel thioridazine derivatives active against drug-resistant tuberculosis

“…TZ was successfully demethylated by treatment with 1-chloro-ethyl-chloroformate in refluxing DCE [25] followed by hydrolysis with MeOH under reflux, leading to derivative 3. Reductive amination of 3 with different aldehydes/ketones led to the final N-alkyl-derivatives 4a-c in good yields (62-68%).…”