Year-end Sale % OFF 
Abstract
The calcium-activated chloride channel (CaCC) TMEM16A plays crucial roles in regulating neuronal excitability, smooth muscle contraction, fluid secretion and gut motility. While opening of TMEM16A requires binding of intracellular Ca2+, prolonged Ca2+-dependent activation results in channel desensitization or rundown, the mechanism of which is unclear. Here we show that phosphatidylinositol (4,5)-bisphosphate (PIP2) regulates TMEM16A channel activation and desensitization via binding to a putative binding site at the cytosolic interface of transmembrane segments (TMs) 3–5. We further demonstrate that the ion-conducting pore of TMEM16A is constituted of two functionally distinct modules: a Ca2+-binding module formed by TMs 6–8 and a PIP2-binding regulatory module formed by TMs 3–5, which mediate channel activation and desensitization, respectively. PIP2 dissociation from the regulatory module results in ion-conducting pore collapse and subsequent channel desensitization. Our findings thus provide key insights into the mechanistic understanding of TMEM16 channel gating and lipid-dependent regulation.
Highlights
The calcium-activated chloride channel (CaCC) TMEM16A plays crucial roles in regulating neuronal excitability, smooth muscle contraction, fluid secretion and gut motility
Consistent with a previous observation[22], we found that diC8 PIP2 substantially attenuates TMEM16A desensitization in a dosedependent manner in the presence of 100 μM intracellular Ca2+ (Fig. 1d–f)
Combining electrophysiology with intensive structure-guided mutagenesis, we identify the molecular mechanism underlying the multifaceted role of PIP2 in modulating TMEM16A
Summary
The calcium-activated chloride channel (CaCC) TMEM16A plays crucial roles in regulating neuronal excitability, smooth muscle contraction, fluid secretion and gut motility. The Ca2+-binding site is formed by highly conserved acidic residues from TMs 6, 7, and 86,7,9,14,15 This architecture suggests that Ca2+ binding to the Ca2+-sensing TMs 6–8 directly gates ion permeation in TMEM16A. This phenomenon has been alternatively referred to as “rundown”, “desensitization” or “inactivation” in the literature; we will use desensitization and rundown interchangeably to describe the time-dependent TMEM16A current decay in this work This desensitized state was likely captured in the recent Ca2+-bound TMEM16A structures, where the putative ion permeation pore adopts a nonconductive collapsed configuration even though both Ca2+ binding sites were fully occupied (Fig. 1a)[7,9]. Our results provide a structural framework to understand the interplay between PIP2 regulation and Ca2+ activation during channel gating in the TMEM16A–CaCC
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
