ChronicJNK-AP-1 signaling directs proteome ordering via transcriptional aggresome programming
Hypothesis
It's not only driving the inflammatory SASP; chronic JNK-AP-1 activation also transcriptionally programs the aggresome and JUNQ/IPOD compartments to sequester misfolded proteins into ordered inclusions, converting proteotoxic stress into a cytoprotective state.
Mechanistic Basis
AP-1 dimers (c-Jun/ATF2) bind promoter regions of genes encoding aggresome machinery – HDAC6, p62/SQSTM1, and ubiquitin‑binding proteins – as well as factors that promote JUNQ/IPOD sequestration such as BAG3 and HSP70 co‑chaperones. This transcriptional shift occurs downstream of sustained JNK phosphorylation, which we propose acts as a molecular switch that redirects the cell from transient stress buffering to a stable, ordered proteome depot.
Predictions & Experimental Design
- In senescent fibroblasts induced by ROS or oncogenic stress, ChIP‑seq for c‑Jun will show enrichment at HDAC6, p62, and BAG3 promoters compared with proliferating controls.
- siRNA‑mediated knock‑down of c‑Jun will reduce aggresome formation (measured by HDAC6‑dependent vimentin cage formation and p62‑positive inclusions) while increasing soluble oligomeric species detected by A11 antibody.
- Conversely, forced expression of a constitutively active c‑Jun‑VP16 fusion will enhance aggresome markers and lower cytotoxicity despite persistent SASP secretion.
- Pharmacological inhibition of JNK (SP600125) will blunt both SASP upregulation and aggresome gene expression, uncoupling the two outputs.
Potential Implications
If aggregation represents a protective, AP‑1‑driven sequestration program, then dissolving aggregates in senescent cells could unleash toxic oligomers and accelerate tissue dysfunction. Therapeutic strategies that modulate JNK‑AP-1 activity might need to preserve the cytoprotective arm while inhibiting the inflammatory arm, suggesting a bifurcated targeting approach.
Key citations: JNK‑driven SASP via c‑Jun phosphorylation [1]; ROS‑mediated JNK activation linking to senescence [2]; JNK‑dependent immune evasion and cell‑cycle arrest [3]; upstream proteasome stress sensing through IRE1α/TRAF2/ASK1 [4]