Figure 3.
Examples of integration among the UPR apoptosis pathways. (a) In the simplest scenario, differential apoptotic signalling downstream of CHOP and IRE1 may lead to only partial cell death responses, and so the full apoptotic response may require activation of both pathways. (b) Both pathways can promote changes in Bcl-2 family protein expression or activity that favour cell death. (c) Both pathways can promote JNK activation, which when prolonged, can trigger cell death. Note that one of the mechanisms by which activated JNK leads to apoptosis is through Bax–Bak activation, possibly leading to further integration (purple dotted arrow). See text for details and for other possible areas of integration.