Several ER/PM tethers tested other than TMEM24 and C2CD2 display no preference for cell-adjacent ER/PM junctions. ER/PM junctions positive for exogenously expressed E-Syt2-eGFP (A), Kv2.1(S601,607D-eGFP (B), or YFP-STIM1(D76A) (C) in HEK293 cells show no differences in size depending on cell adjacency. Quantification of this data can be found in Fig. 1 B. Plasma membranes were determined using DiI and cell regions traced for ease of identification. Scale bars = 5 μm.