1. Academic Validation
  2. Photocrosslinking-induced CRAC channel-like Orai1 activation independent of STIM1

Photocrosslinking-induced CRAC channel-like Orai1 activation independent of STIM1

  • Nat Commun. 2023 Mar 8;14(1):1286. doi: 10.1038/s41467-023-36458-4.
Lena Maltan # 1 Sarah Weiß # 1 Hadil Najjar # 1 Melanie Leopold 1 Sonja Lindinger 1 Carmen Höglinger 1 Lorenz Höbarth 1 Matthias Sallinger 1 Herwig Grabmayr 1 Sascha Berlansky 1 Denis Krivic 2 Valentina Hopl 1 Anna Blaimschein 1 Marc Fahrner 1 Irene Frischauf 1 Adéla Tiffner 1 Isabella Derler 3
Affiliations

Affiliations

  • 1 Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, A-4020, Linz, Austria.
  • 2 Division of Medical Physics and Biophysics, Gottfried Schatz Research Center, Medical University of Graz, A-8010, Graz, Austria.
  • 3 Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, A-4020, Linz, Austria. Isabella.derler@jku.at.
  • # Contributed equally.
Abstract

CA2+ release-activated CA2+ (CRAC) channels, indispensable for the immune system and various other human body functions, consist of two transmembrane (TM) proteins, the CA2+-sensor STIM1 in the ER membrane and the CA2+ ion channel Orai1 in the plasma membrane. Here we employ genetic code expansion in mammalian cell lines to incorporate the photocrosslinking unnatural Amino acids (UAA), p-benzoyl-L-phenylalanine (Bpa) and p-azido-L-phenylalanine (Azi), into the Orai1 TM domains at different sites. Characterization of the respective UAA-containing Orai1 mutants using CA2+ imaging and electrophysiology reveal that exposure to UV LIGHT triggers a range of effects depending on the UAA and its site of incorporation. In particular, photoactivation at A137 using Bpa in Orai1 activates CA2+ currents that best match the biophysical properties of CRAC channels and are capable of triggering downstream signaling pathways such as nuclear factor of activated T-cells (NFAT) translocation into the nucleus without the need for the physiological activator STIM1.

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