The pharmacology of the TMEM16A channel: therapeutic opportunities

Identification of a druggable pocket of the calcium-activated chloride channel TMEM16A in its open state

“…The structures of TMEM16A and its family members have been recently determined with the calcium-activated gating mechanism elucidated ( 6 ). High-throughput drug screening and computer-aided drug design have identified an array of TMEM16A activators and potentiators, among which ETX001, a potentiator of TMEM16A, has entered clinical trials as therapeutic agent for cystic fibrosis ( 7 ). Meanwhile, a large number of TMEM16A inhibitors have been identified, including natural products Cepharanthine ( 8 ), Evodiamine ( 9 ), Honokiol ( 10 ), and Luteolin ( 11 ) and synthetic compounds Ani9 ( 12 ), CaCC inh -A01 ( 13 ), T16A inh -A01 ( 14 ), Monna ( 15 ), and 4-arylthiophene-3-carboxylic acid ( 16 ).…”

Identification of Druggable Binding Sites and Small Molecules as Modulators of TMC1

“…Therefore, we investigated whether inhibitors of both TMC1 and TMEM16A proteins share common pharmacophoric features. To do this, we used Phase to virtually screen the 10 known modulators of TMEM16A (MONNA, Ani9, TM inh -23, Zafirlukast, Niclosamide, Evodiamine, Tannic acid, theaflavine, E act , and F act ) 134,135 against the 10 TMC1 pharmacophores ( Table 1 , and Supp Figures 2 and 4 ). Our results suggest that both cepharanthine and theaflavine share the same APRR pharmacophore.…”

“…To investigate these differences, we compared the TMC1 and TMEM16A pores, carrying out a structural analysis of our open-like state of the mm TMC1 model and the reported TMEM16 structure (PDB: 5OYB) 136 . This structure was previously used to predict the binding mode of cepharanthine and theaflavine only at the top site of the pore region 134,135 . Our analysis confirmed a closed-pore conformation at the predicted upper binding pocked of the TMEM16A structure, corresponding to the top site within the TMC1 pore ( Supp Figure 4I-L ).…”

“…(G-H) Structural alignment of cepharantine and Ani9 with the ARR-2 vector features, respectively. Theaflavine and Ani9 are inhibitors of TMEM16A 135 . (I) Cartoon representation of an open-like conformation of TMC1.…”

PIP2 and Ca2+ regulation of TMEM16A currents in excised inside-out patches

“…TMEM16A channels are homodimers, with each subunit comprising ten transmembrane domains, large intracellular N- and C-terminal domains, a membrane-embedded Ca 2+ binding site, and an independently operating Cl − conducting pore (Al-Hosni, Ilkan, Agostinelli & Tammaro, 2022; Hawn, Akin, Hartzell, Greenwood & Leblanc, 2021; Shi et al, 2020). Five conserved amino acids in transmembrane domains 6-8 form the Ca 2+ binding site, with each site capable of accommodating two Ca 2+ ions (Brunner, Lim, Schenck, Duerst & Dutzler, 2014; Dang et al, 2017; Paulino, Kalienkova, Lam, Neldner & Dutzler, 2017).…”