TY - JOUR
T1 - Intracellular Loop in the Brain Isoforms of Anoctamin 2 Channels Regulates Calcium-dependent Activation
AU - Lee, Dongsu
AU - Lim, Hocheol
AU - Lee, Jungryun
AU - Ha, Go Eun
AU - No, Kyoung Tai
AU - Cheong, Eunji
N1 - Publisher Copyright:
© Experimental Neurobiology 2023.
PY - 2023/6
Y1 - 2023/6
N2 - Anoctamin 2 (ANO2 or TMEM16B), a calcium-activated chloride channel (CaCC), performs diverse roles in neurons throughout the central nervous system. In hippocampal neurons, ANO2 narrows action potential width and reduces postsynaptic depolarization with high sensitivity to Ca2+ at relatively fast kinetics. In other brain regions, including the thalamus, ANO2 mediates activity-dependent spike frequency adaptations with low sensitivity to Ca2+ at relatively slow kinetics. How this same channel can respond to a wide range of Ca2+ levels remains unclear. We hypothesized that splice variants of ANO2 may contribute to its distinct Ca2+ sensitivity, and thus its diverse neuronal functions. We identified two ANO2 isoforms expressed in mouse brains and examined their electrophysiological properties: isoform 1 (encoded by splice variants with exons 1a, 2, 4, and 14) was expressed in the hippocampus, while isoform 2 (encoded by splice variants with exons 1a, 2, and 4) was broadly expressed throughout the brain, including in the cortex and thalamus, and had a slower calcium-dependent activation current than isoform 1. Computational modeling revealed that the secondary structure of the first intracellular loop of isoform 1 forms an entrance cavity to the calcium-binding site from the cytosol that is relatively larger than that in isoform 2. This difference provides structural evidence that isoform 2 is involved in accommodating spike frequency, while isoform 1 is involved in shaping the duration of an action potential and decreasing postsynaptic depolarization. Our study highlights the roles and molecular mechanisms of specific ANO2 splice variants in modulating neuronal functions.
AB - Anoctamin 2 (ANO2 or TMEM16B), a calcium-activated chloride channel (CaCC), performs diverse roles in neurons throughout the central nervous system. In hippocampal neurons, ANO2 narrows action potential width and reduces postsynaptic depolarization with high sensitivity to Ca2+ at relatively fast kinetics. In other brain regions, including the thalamus, ANO2 mediates activity-dependent spike frequency adaptations with low sensitivity to Ca2+ at relatively slow kinetics. How this same channel can respond to a wide range of Ca2+ levels remains unclear. We hypothesized that splice variants of ANO2 may contribute to its distinct Ca2+ sensitivity, and thus its diverse neuronal functions. We identified two ANO2 isoforms expressed in mouse brains and examined their electrophysiological properties: isoform 1 (encoded by splice variants with exons 1a, 2, 4, and 14) was expressed in the hippocampus, while isoform 2 (encoded by splice variants with exons 1a, 2, and 4) was broadly expressed throughout the brain, including in the cortex and thalamus, and had a slower calcium-dependent activation current than isoform 1. Computational modeling revealed that the secondary structure of the first intracellular loop of isoform 1 forms an entrance cavity to the calcium-binding site from the cytosol that is relatively larger than that in isoform 2. This difference provides structural evidence that isoform 2 is involved in accommodating spike frequency, while isoform 1 is involved in shaping the duration of an action potential and decreasing postsynaptic depolarization. Our study highlights the roles and molecular mechanisms of specific ANO2 splice variants in modulating neuronal functions.
KW - Anoctamin 2
KW - Calcium
KW - Calcium-activated chloride channels
KW - Molecular modeling
KW - Secondary protein structure
KW - Splice variants
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U2 - 10.5607/en22045
DO - 10.5607/en22045
M3 - Article
AN - SCOPUS:85165297383
SN - 1226-2560
VL - 32
SP - 13
EP - 146
JO - Experimental Neurobiology
JF - Experimental Neurobiology
IS - 3
ER -