Figure 2

Upregulation of SERCA-mediated ⁴⁵Ca²⁺ uptake into microsomes prepared after exposure of PC12 cells to various types of ER stress. EGTA (2.5 mM), brefeldin A (BFA) 5 μg/ml, tunicamycin (Tun) 10 g/ml, or DTT 1 mM were present in the culture medium for the indicated times prior to cell harvest (in "4h+3" condition, after 4 h in the presence of DTT, control medium was reintroduced for 3 h prior to cell harvest). The microsomes were prepared and ⁴⁵Ca²⁺ uptake determined as described in Materials and Methods. For all conditions, the thapsigargin-sensitive portion of the uptake (see Figs. 1A,B) was calculated and expressed as % of the corresponding thapsigargin-sensitive portion for untreated cells, as determined in parallel for each separate condition. (None of the treatments affected the thapsigargin-insensitive portion of ⁴⁵Ca²⁺ uptake). For each condition, statistical significance of the difference between these pairs of values was determined using 2-tailed student's t-test, with P values and numbers of independent experiments (n) as indicated. Bars represent SEMs.