Fig. 7.

Activation of SIK, IRE1 and PERK and SIK to form Sec bodies. Blue pathway, Sec bodies can form upon high-salt stress (SCH150) through SIK activation, which, when strong is sufficient. A moderate salt stress also activates SIKs, but it is not enough to stimulate Sec body formation. Red pathway: amino acid starvation in KRB leads to IRE1, PERK and SIK activation leading to Sec body formation (mimicked by SCH100+DTT). IRE1 and PERK activation are necessary but not sufficient. In green are features appearing upon KRB incubation, such as cytoplasm acidification, a decrease in the cytoplasmic ATP concentration and the stimulation of the UPR that we propose to be a key factor in Sec body formation.