Inhibition of the proton-activated chloride channel PAC by PIP2

Abstract

Proton-Activated Chloride (PAC) channel is a ubiquitously expressed pH-sensing ion channel, encoded by PACC1 (TMEM206). PAC regulates endosomal acidification and macropinosome shrinkage by releasing chloride from the organelle lumens. It is also found at the cell surface, where it is activated under pathological conditions related to acidosis and contributes to acid-induced cell death. However, the pharmacology of the PAC channel is poorly understood. Here, we report that phosphatidylinositol (4,5)-bisphosphate (PIP2) potently inhibits PAC channel activity. We solved the cryo-electron microscopy structure of PAC with PIP2 at pH 4.0 and identified its putative binding site, which, surprisingly, locates on the extracellular side of the transmembrane domain (TMD). While the overall conformation resembles the previously resolved PAC structure in the desensitized state, the TMD undergoes remodeling upon PIP2-binding. Structural and electrophysiological analyses suggest that PIP2 inhibits the PAC channel by stabilizing the channel in a desensitized-like conformation. Our findings identify PIP2 as a new pharmacological tool for the PAC channel and lay the foundation for future drug discovery targeting this channel.

Assessing the Causal Relationships Between Lipid Species and Stroke by Using Mendelian Randomization

“…Its abnormal metabolism has been associated with various diseases [29,30]. Andres et al demonstrated that phosphatidylinositol bisphosphate strongly inhibits proton-activated chloride channels, thereby preventing chloride entry into the cells and reducing acid-induced brain damage [31,32]. Studies on phosphatidylinositol and brain injury often focus on the neuroprotective pathway of phosphoinositide-3-kinase (PI3K)-protein kinase B (Akt) [33,34], while other reports have indicated the anti-apoptotic effects of phosphatidylinositol-4-kinase alpha (PI4KA) in the brain [35].…”

CBA (4-chloro-2-(2-chlorophenoxy)acetamido) benzoic acid) inhibits TMEM206 mediated currents and TMEM206 does not contribute to acid-induced cell death in colorectal cancer cells

“… • Interestingly, Mihaljevic et al reported that PIP 2 inhibits TMEM206 by stabilizing the channel in a desensitized-like conformation at low pH (pH < 5). Furthermore PIP 2 -mediated current inhibition was incomplete at pH 5.0 ( Mihaljević et al, 2023 ). CBA barely inhibits TMEM206-mediated currents at pH 6.0 when TMEM206 is transiently overexpressed in TMEM206 KO HCT116 cells ( Figure 5B, C ).…”

“…In addition, phloretin ( Wang et al, 2007 ) and pregnenolone sulphate (PS) ( Drews et al, 2014 ) have been reported as PAORAC/ASOR/TMEM206 inhibitors, however, phloretin is an inhibitor of the sodium glucose cotransporter (SGLT) ( Habtemariam, 2023 ) and pregnenolone sulphate an activator of TRPM3 ( Wagner et al, 2008 ). A recent study identified phosphatidylinositol-4,5-bisphosphate (PIP 2 ) as a novel inhibitor of TMEM206 ( Mihaljević et al, 2023 ). But, PIP 2 has also been reported as a modulator of a diverse set of ion channels ( Suh and Hille, 2008 ; Gada and Logothetis, 2022 ), including the Cl − channels TMEM16A and TMEM16B ( Ta et al, 2017 ).…”