Fig. 1.

Salt stress activates the SIKs, which are involved in Sec body formation. (A,A′) Immunofluorescence (IF) visualization of endogenous Sec16 in S2 cells growing in Schneider's medium (Sch) and in cells incubated in KRB (A). Note the difference in the Sec16 pattern; Sec16 is at ER exit sites in growing cells and in Sec bodies in cells incubated in KRB. Upon KRB incubation, ERES remodel into larger structures, the Sec bodies, that are brighter than ERES. (B) IF visualization of Sec body formation (marked by Sec16) in cells incubated in Schneider's medium supplemented with 10 mM sodium bicarbonate and 150 mM of NaCl (SCH150) for 4 h at 26°C. (C) Quantification of Sec body formation (marked by Sec16) in cells incubated in Sch, KRB, KRB with lower NaCl (containing only 60 mM NaCl) and SCH150 for 4 h at 26°C as well as SCH150 and then in Sch for 1 h (reversion), showing that SCH150-induced Sec bodies are formed reversibly. (D,D′) Western blot of S2 cells protein extract after incubation in Schneider's medium (Sch), KRB and SCH150 with and without HG-9-91-01 (5 µM) for 4 h at 26°C blotted for HDAC4-p and α-tubulin. Quantification of the ratio HDAC4-p to α-tubulin (D′). (E,E′) IF Visualization (E) and quantification (E′) of Sec body formation (marked by Sec16) in cells incubated in SCH150 supplemented or not with the SIK inhibitor HG-9-91-01 (HG, 5 µM), the Src inhibitor dasatinib (Da, 20 µM) and the p38 MAPK inhibitor SB203580 (SB, 30 µM) for 4 h at 26°C. Scale bars: 10 µm. Errors bars: s.e.m.