Department of Neuroscience, Howard Hughes Medical Institute, The Scripps Research Institute, La Jolla, United States; Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States
Kei Saotome
Department of Neuroscience, Howard Hughes Medical Institute, The Scripps Research Institute, La Jolla, United States; Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States
Adrienne E Dubin
Department of Neuroscience, Howard Hughes Medical Institute, The Scripps Research Institute, La Jolla, United States
Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States
Christopher A Cottrell
Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States
Stuart M Cahalan
Department of Neuroscience, Howard Hughes Medical Institute, The Scripps Research Institute, La Jolla, United States
Zhaozhu Qiu
Genomics Institute of the Novartis Research Foundation, San Diego, United States
Gunhee Hong
Department of Neuroscience, Howard Hughes Medical Institute, The Scripps Research Institute, La Jolla, United States
Christopher S Crowley
Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States; Department of Dermatology, University of California, San Diego, San Diego, United States
Tess Whitwam
Department of Neuroscience, Howard Hughes Medical Institute, The Scripps Research Institute, La Jolla, United States
Wen-Hsin Lee
Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States
Andrew B Ward
Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States
SWELL1 (LRRC8A) is the only essential subunit of the Volume Regulated Anion Channel (VRAC), which regulates cellular volume homeostasis and is activated by hypotonic solutions. SWELL1, together with four other LRRC8 family members, potentially forms a vastly heterogeneous cohort of VRAC channels with different properties; however, SWELL1 alone is also functional. Here, we report a high-resolution cryo-electron microscopy structure of full-length human homo-hexameric SWELL1. The structure reveals a trimer of dimers assembly with symmetry mismatch between the pore-forming domain and the cytosolic leucine-rich repeat (LRR) domains. Importantly, mutational analysis demonstrates that a charged residue at the narrowest constriction of the homomeric channel is an important pore determinant of heteromeric VRAC. Additionally, a mutation in the flexible N-terminal portion of SWELL1 affects pore properties, suggesting a putative link between intracellular structures and channel regulation. This structure provides a scaffold for further dissecting the heterogeneity and mechanism of activation of VRAC.
