• the Korean Society for Brain and Neural Sciences


Original Article

Exp Neurobiol 2019; 28(2): 183-215

Published online April 30, 2019

© The Korean Society for Brain and Neural Sciences

Tweety-homolog (Ttyh) Family Encodes the Pore-forming Subunits of the Swelling-dependent Volume-regulated Anion Channel (VRACswell) in the Brain

Young-Eun Han1,2,3, Jea Kwon1,3,4, Joungha Won1,3,5, Heeyoung An1,3,4, Minwoo Wendy Jang1,3,4, Junsung Woo3, Je Sun Lee6, Min Gu Park1,3,4, Bo-Eun Yoon7, Seung Eun Lee8, Eun Mi Hwang3, Jae-Young Jung2,3, Hyungju Park6, Soo-Jin Oh3,9, and C. Justin Lee1,2,3*

1Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea.

2Department of Neuroscience, Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea.

3Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.

4KU-KIST, Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Korea.

5Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.

6Molecular Neurobiology Laboratory, Dept. of Structure and Function of Neural Network, Korea Brain Research Institute, Daegu 41068, Korea.

7Department of molecular biology, Dankook University, Cheonan 31116, Korea.

8Virus Facility, Research Animal Resource Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.

9Convergence Research Center for Diagnosis, Treatment and Care System of Dementia, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.

Correspondence to: *To whom correspondence should be addressed.
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Received: April 16, 2019; Revised: April 23, 2019; Accepted: April 25, 2019

In the brain, a reduction in extracellular osmolality causes water-influx and swelling, which subsequently triggers Cl- and osmolytes-efflux via volume-regulated anion channel (VRAC). Although LRRC8 family has been recently proposed as the pore-forming VRAC which is activated by low cytoplasmic ionic strength but not by swelling, the molecular identity of the pore-forming swelling-dependent VRAC (VRACswell) remains unclear. Here we identify and characterize Tweety-homologs (TTYH1, TTYH2, TTYH3) as the major VRACswell in astrocytes. Gene-silencing of all Ttyh1/2/3 eliminated hypo-osmotic-solution-induced Cl conductance (ICl,swell) in cultured and hippocampal astrocytes. When heterologously expressed in HEK293T or CHO-K1 cells, each TTYH isoform showed a significant ICl,swell with similar aquaporin-4 dependency, pharmacological properties and glutamate permeability as ICl,swell observed in native astrocytes. Mutagenesis-based structure-activity analysis revealed that positively charged arginine residue at 165 in TTYH1 and 164 in TTYH2 is critical for the formation of the channel-pore. Our results demonstrate that TTYH family confers the bona fide VRACswell in the brain.

Graphical Abstract

Keywords: Volume-regulated anion channel, VRAC, Tweety-homolog, Ttyh, Volume regulation