Autophagy activation by NFkappaB is essential for cell survival after heat shock.
The heat shock response is a widely described defense mechanism during which the preferential expression of heat shock proteins (Hsps) helps the cell to recover from thermal damages such as protein denaturation/aggregation. We have previously reported that NFkappaB transcription factor is activated during the recovery period after heat shock. In this study, we analyze the consequences of NFkappaB activation during heat shock recovery, by comparing the heat shock response of NFkappaB competent and incompetent (p65/RelA-depleted) cells. We demonstrate for the first time that NFkappaB plays a major and crucial role during the heat shock response by activating autophagy, which increases survival of heat-treated cells. Indeed, we observed that autophagy is not activated during heat shock recovery and cell death is strongly increased in NFkappaB incompetent cells. Moreover, if autophagy is artificially induced in these cells, the cytotoxicity of heat shock is turned back to normal. We show that despite a post-heat shock increase of Beclin 1 level in NFkappaB competent cells, neither Beclin 1/class III PI3K complex, Bcl(2)/Bcl-X(L) nor mTOR kinase are NFkappaB targets whose modulation of expression could be responsible for NFkappaB activation of autophagy during heat shock recovery. In contrast, we demonstrate that aberrantly folded/aggregated proteins are prime events in the signaling pathway leading to NFkappaB mediated autophagy after heat shock. Hence, our findings demonstrate that NFkappaB-induced autophagy during heat shock recovery is an additional cell response to HS-induced protein denaturation/aggregation; this mechanism increases cell survival, probably through clearance of irreversibly damaged proteins.
Nivon
Mathieu
M
Université de Lyon, Lyon, France.
Richet
Emma
E
Codogno
Patrice
P
Arrigo
André-Patrick
AP
Kretz-Remy
Carole
C
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D019556:COS Cells; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002522:Chlorocebus aethiops; D019610:Cytoprotection / Q000187:drug effects; D005990:Glycerol / Q000494:pharmacology; D006367:HeLa Cells; D018869:Heat-Shock Response / Q000187:drug effects; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000378:metabolism; D051996:Transcription Factor RelA / Q000172:deficiency / Q000378:metabolism
C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D016328:NF-kappa B; D010714:Phosphatidylethanolamines; D051996:Transcription Factor RelA; C483858:phosphatidylethanolamine; D005990:Glycerol