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

  • Exp Neurobiol. 2019 Apr;28(2):183-215. doi: 10.5607/en.2019.28.2.183.
Young-Eun Han  1  2  3 ,  Jea Kwon  1  3  4 ,  Joungha Won  1  3  5 ,  Heeyoung An  1  3  4 ,  Minwoo Wendy Jang  1  3  4 ,  Junsung Woo  3 ,  Je Sun Lee  6 ,  Min Gu Park  1  3  4 ,  Bo-Eun Yoon  7 ,  Seung Eun Lee  8 ,  Eun Mi Hwang  3 ,  Jae-Young Jung  2  3 ,  Hyungju Park  6 ,  Soo-Jin Oh  3  9 ,  C Justin Lee  1  2  3
Affiliations
  • 1. Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea.
  • 2. Department of Neuroscience, Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea.
  • 3. Center for Glia-Neuron Interaction, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.
  • 4. KU-KIST, Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Korea.
  • 5. Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
  • 6. Molecular Neurobiology Laboratory, Dept. of Structure and Function of Neural Network, Korea Brain Research Institute, Daegu 41068, Korea.
  • 7. Department of molecular biology, Dankook University, Cheonan 31116, Korea.
  • 8. Virus Facility, Research Animal Resource Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.
  • 9. Convergence Research Center for Diagnosis, Treatment and Care System of Dementia, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.
PMID: 31138989 DOI: 10.5607/en.2019.28.2.183
Abstract

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.

Keywords
Ttyh; Tweety-homolog; VRAC; Volume regulation; Volume-regulated anion channel.