Calmodulin-dependent activation of the epithelial calcium-dependent chloride channel TMEM16A.
TMEM16A (anoctamin 1, Ano1), a member of a family of 10 homologous proteins, has been shown to form an essential component of Ca(2+)-activated Cl(-) channels. TMEM16A-null mice exhibit severe defects in epithelial transport along with tracheomalacia and death within 1 mo after birth. Despite its outstanding physiological significance, the mechanisms for activation of TMEM16A remain obscure. TMEM16A is activated on increase in intracellular Ca(2+), but it is unclear whether Ca(2+) binds directly to the channel or whether additional components are required. We demonstrate that TMEM16A is strictly membrane localized and requires cytoskeletal interactions to be fully activated. Despite the need for cytosolic ATP for full activation, phosphorylation by protein kinases is not required. In contrast, the Ca(2+) binding protein calmodulin appears indispensable and interacts physically with TMEM16A. Openers of small- and intermediate-conductance Ca(2+)-activated potassium channels known to interact with calmodulin, such as 1-EBIO, DCEBIO, or riluzole, also activated TMEM16A. These results reinforce the use of these compounds for activation of electrolyte secretion in diseases such as cystic fibrosis.
Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
Yuemin
Y
Tian
Patthara
P
Kongsuphol
Martin
M
Hug
Jiraporn
J
Ousingsawat
Ralph
R
Witzgall
Rainer
R
Schreiber
Karl
K
Kunzelmann
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000075369:Anoctamin-1; D001562:Benzimidazoles / Q000494:pharmacology; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002147:Calmodulin / Q000378:metabolism; D018118:Chloride Channels / Q000235:genetics* / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003550:Cystic Fibrosis / Q000378:metabolism*; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D057809:HEK293 Cells; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D018408:Patch-Clamp Techniques; D010766:Phosphorylation / Q000502:physiology; D020545:Respiratory Mucosa / Q000166:cytology; D014132:Trachea / Q000166:cytology
C531181:ANO1 protein, mouse; D000075369:Anoctamin-1; D001562:Benzimidazoles; D002120:Calcium Channel Agonists; D002147:Calmodulin; D018118:Chloride Channels; D002712:Chlorides; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496925:Kcnn4 protein, mouse; D008565:Membrane Proteins; D000255:Adenosine Triphosphate; C102635:1-ethyl-2-benzimidazolinone; D002118:Calcium