title: Preassociated apocalmodulin mediates Ca2+-dependent sensitization of activation and inactivation of TMEM16A/16B Ca2+-gated Cl- channels.
abstract: Ca(2+)-activated chloride currents carried via transmembrane proteins TMEM16A and TMEM16B regulate diverse processes including mucus secretion, neuronal excitability, smooth muscle contraction, olfactory signal transduction, and cell proliferation. Understanding how TMEM16A/16B are regulated by Ca(2+) is critical for defining their (patho)/physiological roles and for rationally targeting them therapeutically. Here, using a bioengineering approach--channel inactivation induced by membrane-tethering of an associated protein (ChIMP)--we discovered that Ca(2+)-free calmodulin (apoCaM) is preassociated with TMEM16A/16B channel complexes. The resident apoCaM mediates two distinct Ca(2+)-dependent effects on TMEM16A, as revealed by expression of dominant-negative CaM1234. These effects are Ca(2+)-dependent sensitization of activation (CDSA) and Ca(2+)-dependent inactivation (CDI). CDI and CDSA are independently mediated by the N and C lobes of CaM, respectively. TMEM16A alternative splicing provides a mechanism for tuning apoCaM effects. Channels lacking splice segment b selectively lost CDI, and segment a is necessary for apoCaM preassociation with TMEM16A. The results reveal multidimensional regulation of TMEM16A/16B by preassociated apoCaM and introduce ChIMP as a versatile tool to probe the macromolecular complex and function of Ca(2+)-activated chloride channels.
authors.affiliation: Departments of Biochemistry and Molecular Biophysics and wayne@xtl.cumc.columbia.edu ty2190@columbia.edu hc2405@columbia.edu.
authors.forename: Tingting
authors.initials: T
authors.lastname: Yang
authors.affiliation: Departments of Biochemistry and Molecular Biophysics and Physiology and Cellular Biophysics, College of Physicians and Surgeons, Columbia University, New York, NY 10032 wayne@xtl.cumc.columbia.edu ty2190@columbia.edu hc2405@columbia.edu.
authors.forename: Wayne A
authors.initials: WA
authors.lastname: Hendrickson
authors.affiliation: Physiology and Cellular Biophysics, College of Physicians and Surgeons, Columbia University, New York, NY 10032 wayne@xtl.cumc.columbia.edu ty2190@columbia.edu hc2405@columbia.edu.
authors.forename: Henry M
authors.initials: HM
authors.lastname: Colecraft
mesh_terms: D000075369:Anoctamin-1; D000075368:Anoctamins; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000502:physiology*; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D009363:Neoplasm Proteins / Q000235:genetics / Q000502:physiology*; D012326:RNA Splicing
chemical_list: C476213:ANO1 protein, human; C521849:ANO2 protein, human; D000075369:Anoctamin-1; D000075368:Anoctamins; D002147:Calmodulin; D018118:Chloride Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D002118:Calcium
keywords: TMEM16A; anoctamin1; calcium-activated chloride channel; calmodulin