TMEM63 proteins function as monomeric high-threshold mechanosensitive ion channels

Wang Zheng; Shaun Rawson; Zhangfei Shen; Elakkiya Tamilselvan; Harper E Smith; Julia Halford; Chen Shen; Swetha E Murthy; Maximilian H Ulbrich; Marcos Sotomayor; Tian-Min Fu; Jeffrey R Holt

doi:10.1016/j.neuron.2023.07.006

TMEM63 proteins function as monomeric high-threshold mechanosensitive ion channels

Neuron. 2023 Oct 18;111(20):3195-3210.e7. doi: 10.1016/j.neuron.2023.07.006. Epub 2023 Aug 4.

Authors

Affiliations

¹ Departments of Otolaryngology & Neurology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA. Electronic address: wang.zheng@childrens.harvard.edu.
² Harvard Cryo-Electron Microscopy Center for Structural Biology, Harvard Medical School, Boston, MA 02115, USA; Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
³ Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH 43210, USA.
⁴ Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Biophysics Program, The Ohio State University, Columbus, OH 43210, USA.
⁵ Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA.
⁶ Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA.
⁷ BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany; Internal Medicine IV, University of Freiburg Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany.
⁸ Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH 43210, USA. Electronic address: fu.978@osu.edu.
⁹ Departments of Otolaryngology & Neurology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA. Electronic address: jeffrey.holt@childrens.harvard.edu.

PMID: 37543036
PMCID: PMC10592209 (available on 2024-10-18)
DOI: 10.1016/j.neuron.2023.07.006

Abstract

OSCA/TMEM63s form mechanically activated (MA) ion channels in plants and animals, respectively. OSCAs and related TMEM16s and transmembrane channel-like (TMC) proteins form homodimers with two pores. Here, we uncover an unanticipated monomeric configuration of TMEM63 proteins. Structures of TMEM63A and TMEM63B (referred to as TMEM63s) revealed a single highly restricted pore. Functional analyses demonstrated that TMEM63s are bona fide mechanosensitive ion channels, characterized by small conductance and high thresholds. TMEM63s possess evolutionary variations in the intracellular linker IL2, which mediates dimerization in OSCAs. Replacement of OSCA1.2 IL2 with TMEM63A IL2 or mutations to key variable residues resulted in monomeric OSCA1.2 and MA currents with significantly higher thresholds. Structural analyses revealed substantial conformational differences in the mechano-sensing domain IL2 and gating helix TM6 between TMEM63s and OSCA1.2. Our studies reveal that mechanosensitivity in OSCA/TMEM63 channels is affected by oligomerization and suggest gating mechanisms that may be shared by OSCA/TMEM63, TMEM16, and TMC channels.

Keywords: IL2; OSCA; TM6; TMC; TMEM16; TMEM63; high-threshold; ion channel; mechanosensitive; oligomerization.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Animals
Interleukin-2* / genetics
Interleukin-2* / metabolism
Ion Channels* / metabolism
Mutation / genetics

Substances

Interleukin-2
Ion Channels

Abstract

Publication types

MeSH terms

Substances

Grants and funding