Untethered STIM1 fragments interact with Orai1-S or with the R429C Orai1-SS mutant.
A, schematic of Orai1, the SOAR/CAD-like S1C fragment, and the Orai1-SS channels used in this work. B, summary of current densities (n = 5–8 cells, left panel) and representative plots of the current-voltage relationship (right panel) of currents recorded from cells expressing Orai1-S alone or from cells co-expressing S1C together with Orai1 or Orai1-S. pF, picofarad. C, summary of current densities (n = 5 cells, left panel) and representative plots of the current-voltage relationship (right panel) recorded from cells expressing Orai1-SS with the loss-of-function mutation R429C alone or together with WT S1C (left panel). D and E, representative fluorescence images (D) and summary of fluorescence densities (E) measured from cells expressing the WT or the R429C Orai1-SS-EGFP mutant (n = 6 regions in each). rfu, relative fluorescence units. Scale bar = 10 μm.