TMEM16 proteins: the long awaited calcium-activated chloride channels?

Flores, Carlos A.; Cid, L. Pablo; Sepúlveda, Francisco V.; Niemeyer, Marı́a Isabel

doi:10.1590/s0100-879x2009005000028

Cited by 31 publications

(34 citation statements)

References 59 publications

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“…With vascular invasion, osteoblasts and osteoclasts enter the cartilage anlagen and start to replace hypertrophic cartilage with trabecular bone and bone marrow. In mice and human, Anoctamins form a family of 10 multitransmembrane proteins that show distinct but overlapping expression patterns in a variety of tissues and cell types during development (11)(12)(13)(14)(15) (reviewed in Flores and colleagues (16) and Galietta (17) ). Recently, Anoctamin1/Tmem16A (Ano1) has been identified as a calcium-activated chloride channel acting in several tissues and cell lines.…”

Section: Introductionmentioning

confidence: 99%

Inactivation of anoctamin-6/Tmem16f, a regulator of phosphatidylserine scrambling in osteoblasts, leads to decreased mineral deposition in skeletal tissues

Ehlen

Chinenkova

Moser

et al. 2012

Journal of Bone and Mineral Research

114

106

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During vertebrate skeletal development, osteoblasts produce a mineralized bone matrix by deposition of hydroxyapatite crystals in the extracellular matrix. Anoctamin6/Tmem16F (Ano6) belongs to a conserved family of transmembrane proteins with chloride channel properties. In addition, Ano6 has been linked to phosphatidylserine (PS) scrambling in the plasma membrane. During skeletogenesis, Ano6 mRNA is expressed in differentiating and mature osteoblasts. Deletion of Ano6 in mice results in reduced skeleton size and skeletal deformities. Molecular analysis revealed that chondrocyte and osteoblast differentiation are not disturbed. However, mutant mice display increased regions of nonmineralized, Ibsp-expressing osteoblasts in the periosteum during embryonic development and increased areas of uncalcified osteoid postnatally. In primary Ano6 À/À osteoblasts, mineralization is delayed, indicating a cell autonomous function of Ano6. Furthermore, we demonstrate that calcium-dependent PS scrambling is impaired in osteoblasts. Our study is the first to our knowledge to reveal the requirement of Ano6 in PS scrambling in osteoblasts, supporting a function of PS exposure in the deposition of hydroxyapatite. ß

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Section: Introductionmentioning

confidence: 99%

Inactivation of anoctamin-6/Tmem16f, a regulator of phosphatidylserine scrambling in osteoblasts, leads to decreased mineral deposition in skeletal tissues

Ehlen

Chinenkova

Moser

et al. 2012

Journal of Bone and Mineral Research

114

106

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“…These results demonstrate that human TMEM16F is an essential component of a Ca 2ϩ -activated Cl Ϫ channel with a Ca 2ϩ sensitivity that is distinct from that of TMEM16A/B and that it is not related to VSOR activity. anoctamin 6; anoctamin 10; Ca 2ϩ -activated Cl Ϫ channel; volumesensitive Cl Ϫ channel Ca 2ϩ -ACTIVATED Cl Ϫ CHANNELS (CaCCs) play important physiological roles in membrane excitability, transepithelial transport, smooth muscle contraction, and other functions (9,11). Although the molecular identity of CaCCs has been unclear for a long time, it has recently been demonstrated that human and mouse transmembrane protein 16A [TMEM16A, also called anoctamin 1 (ANO1)] functions as a major component of CaCCs (5,23,26,37).…”

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confidence: 99%

TMEM16F is a component of a Ca²⁺-activated Cl⁻ channel but not a volume-sensitive outwardly rectifying Cl⁻ channel

Shimizu

Iehara

Sato

et al. 2013

American Journal of Physiology-Cell Physiology

114

157

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TMEM16 (transmembrane protein 16) proteins, which possess eight putative transmembrane domains with intracellular NH2- and COOH-terminal tails, are thought to comprise a Cl− channel family. The function of TMEM16F, a member of the TMEM16 family, has been greatly controversial. In the present study, we performed whole cell patch-clamp recordings to investigate the function of human TMEM16F. In TMEM16F-transfected HEK293T cells but not TMEM16K- and mock-transfected cells, activation of membrane currents with strong outward rectification was found to be induced by application of a Ca2+ ionophore, ionomycin, or by an increase in the intracellular free Ca2+ concentration. The free Ca2+ concentration for half-maximal activation of TMEM16F currents was 9.6 μM, which is distinctly higher than that for TMEM16A/B currents. The outwardly rectifying current-voltage relationship for TMEM16F currents was not changed by an increase in the intracellular Ca2+ level, in contrast to TMEM16A/B currents. The Ca2+-activated TMEM16F currents were anion selective, because replacing Cl− with aspartate− in the bathing solution without changing cation concentrations caused a positive shift of the reversal potential. The anion selectivity sequence of the TMEM16F channel was I− > Br− > Cl− > F− > aspartate−. Niflumic acid, a Ca2+-activated Cl− channel blocker, inhibited the TMEM16F-dependent Cl− currents. Neither overexpression nor knockdown of TMEM16F affected volume-sensitive outwardly rectifying Cl− channel (VSOR) currents activated by osmotic swelling or apoptotic stimulation. These results demonstrate that human TMEM16F is an essential component of a Ca2+-activated Cl− channel with a Ca2+ sensitivity that is distinct from that of TMEM16A/B and that it is not related to VSOR activity.

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“…TMEM16A belongs to a protein family with 10 members encoded by distinct genes (15)(16)(17)(18). There is universal agreement that TMEM16A, and the closely related TMEM16B, are bona fide CaCCs (2,(12)(13)(14)19).…”

mentioning

confidence: 99%

Preassociated apocalmodulin mediates Ca ²⁺ -dependent sensitization of activation and inactivation of TMEM16A/16B Ca ²⁺ -gated Cl ⁻ channels

Yang¹,

Hendrickson

Colecraft

2014

Proc. Natl. Acad. Sci. U.S.A.

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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 CaM 1234 . 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.broadly expressed in mammalian cells regulate diverse physiological functions including: epithelial mucus secretion (1, 2), neuronal excitability (3-5), smooth muscle contraction (6), olfactory transduction (7,8), and cell proliferation (9, 10). Drugs targeting CaCCs are being pursued as therapies for hypertension, cystic fibrosis, asthma, and cancer (1, 9, 11).Three laboratories independently identified the transmembrane protein TMEM16A as the molecular component of a CaCC (12)(13)(14). TMEM16A belongs to a protein family with 10 members encoded by distinct genes (15-18). There is universal agreement that TMEM16A, and the closely related TMEM16B, are bona fide CaCCs (2,(12)(13)(14)19). Consistent with this, TMEM16A knockout mice displayed defective CaCC activity in a variety of epithelia (20)(21)(22), and the olfactory CaCC current was completely abolished in TMEM16B knockout mice (23). Hydropathy analyses suggest TMEM16 proteins have a similar topology with cytosolic N and C termini and eight predicted transmembrane helices (2, 19). Human TMEM16A has four alternatively spliced segments (a-d), differential inclusion of which modify voltage and Ca 2+ sensitivity of resultant channel splice variants (24).CaCCs are highly sensitive to intracellular [Ca 2+ ], displaying graded increases in Cl − current (I Cl ) amplitude as [Ca 2+ ] i is raised from resting levels (∼100 nM) to the 1-to 2-μM range. In some cases, high [Ca 2+ ] i (>10 μM) leads to decreased I Cl amplitude (inactivation) (25-27). The Ca 2+ sensor(s) for Ca 2+ -dependent activation and inactivation (CDA and CDI) of TMEM16A/16B is unknown. There are two possible nonexclusive mechanisms: (i) dire...

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TMEM16 proteins: the long awaited calcium-activated chloride channels?

Cited by 31 publications

References 59 publications

Inactivation of anoctamin-6/Tmem16f, a regulator of phosphatidylserine scrambling in osteoblasts, leads to decreased mineral deposition in skeletal tissues

Inactivation of anoctamin-6/Tmem16f, a regulator of phosphatidylserine scrambling in osteoblasts, leads to decreased mineral deposition in skeletal tissues

TMEM16F is a component of a Ca²⁺-activated Cl⁻ channel but not a volume-sensitive outwardly rectifying Cl⁻ channel

Preassociated apocalmodulin mediates Ca ²⁺ -dependent sensitization of activation and inactivation of TMEM16A/16B Ca ²⁺ -gated Cl ⁻ channels

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TMEM16 proteins: the long awaited calcium-activated chloride channels?

Cited by 31 publications

References 59 publications

Inactivation of anoctamin-6/Tmem16f, a regulator of phosphatidylserine scrambling in osteoblasts, leads to decreased mineral deposition in skeletal tissues

Inactivation of anoctamin-6/Tmem16f, a regulator of phosphatidylserine scrambling in osteoblasts, leads to decreased mineral deposition in skeletal tissues

TMEM16F is a component of a Ca2+-activated Cl− channel but not a volume-sensitive outwardly rectifying Cl− channel

Preassociated apocalmodulin mediates Ca 2+ -dependent sensitization of activation and inactivation of TMEM16A/16B Ca 2+ -gated Cl − channels

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TMEM16F is a component of a Ca²⁺-activated Cl⁻ channel but not a volume-sensitive outwardly rectifying Cl⁻ channel

Preassociated apocalmodulin mediates Ca ²⁺ -dependent sensitization of activation and inactivation of TMEM16A/16B Ca ²⁺ -gated Cl ⁻ channels