Lactacystin and overexpression of CAST, a calpain inhibitor, rescues NCS-1 levels and the calcium signal in SHSY-5Y cells. A, representative Western blot showing that NCS-1 levels are significantly decreased in SHSY-5Y cells treated with paclitaxel and expression of CAST rescued NCS-1 levels. Lane 1, control; lane 2, paclitaxel-treated cells; lane 3, CAST + paclitaxel; lane 4, CAST. B, Representative Western blot showing lactacystin-rescued NCS-1 levels. Lane 1, control; lane 2, paclitaxel-treated cells; lane 3, lactacystin + paclitaxel. C, Western blot analysis shows that either the presence of lactacystin or expression of CAST rescued NCS-1 levels close to that of control cells (n = 5). *, p ≤ 0.05. Error bars, S.E. All treatments were normalized to control cells. D and E, intracellular calcium signal measured in the presence (D) and absence (E) of external calcium. With a 6-h treatment of paclitaxel, calcium transients were reduced 45%. CAST rescued the calcium signal in cells treated for 6 h with paclitaxel to that of control cells (60 cells, n = 3). (A, 1 μm ATP; T, 10 μm thapsigargin).