Figure 3

Function of E-Syts in endoplasmic reticulum membrane and plasma membrane tethering in T cells. (A) Bar graphs showing the PM occupancy of the junctional HRP-tubules in control and DKO HeLa (Ctrl rest: n = 7, Ctrl TG: n = 6, DKO rest: n = 6, DKO TG: n = 7) and Jurkat T (Ctrl rest: n = 13, Ctrl TG: n = 12, DKO rest: n = 15, DKO TG: n = 13) cells. Right panels show representative electron microscopy images of Jurkat T cells (resting and store depleted) expressing HRP-ER and processed for HRP cytochemistry showing ER tubules at the ER–PM junctions (black arrows) and in the cytoplasm (white arrowheads) (Scale bars, 2 μm; Inset, 0.2 μm). *p < 0.05, **p < 0.005, ***p < 0.001. (B) Bar graphs show number of junctional contacts/μm of the PM and length of the Individual Junctional-HRP tubules per section (normalized to the PM circumference) in control (rest: n = 13, TG: n = 12), and DKO (rest: n = 15, TG: n = 13) Jurkat T cells. **p < 0.005, ***p < 0.001. N.S. not significant. (C) SOCE measurement in control, DKO, and DKO Jurkat cells expressing STIM1 or MAPPER. Intracellular stores were passively depleted with thapsigargin (1 μM, TG) in Ca²⁺-free Ringer’s solution, and SOCE was measured by perfusion with 2 mM Ca²⁺-containing Ringer’s solution. Traces show averaged SOCE responses from 30 to 50 cells, and bar graph shows averaged SOCE response (peak – basal) ± S.E.M. from three independent experiments. *p < 0.05.