A chemical screen designed to identify novel inducers of autophagy led to the 
discovery that signal transducer and activator of transcription 3 (STAT3) 
inhibitors can potently stimulate the autophagic flux. Although STAT3 is best 
known as a pro-inflammatory and oncogenic transcription factor, mechanistic 
analyses revealed that autophagy is regulated by the cytoplasmic, not nuclear, 
pool of STAT3. Cytoplasmic STAT3 normally interacts with the eukaryotic 
translation initiation factor 2, subunit 1α, 35kDa (EIF2S1/eIF2α) kinase 
2/protein kinase, RNA-activated (EIF2AK2/PKR), a sensor of double-stranded RNA. 
This interaction, which could be recapitulated using recombinant proteins in 
pull-down experiments, involves the catalytic domain of EIF2AK2 as well as the 
SH2 domain of STAT3, which can adopt a fold similar to that of EIF2S1. Thus, 
STAT3 may act as a competitive inhibitor of EIF2AK2. Indeed, pharmacological or 
genetic inhibition of STAT3 stimulates EIF2AK2-dependent EIF2S1 phosphorylation 
and autophagy. Conversely, the overexpression of wild-type STAT3 as well as of 
STAT3 mutants that cannot be phosphorylated by JAK2 or are excluded from the 
nucleus inhibits autophagy. However, STAT3 mutants that fail to interact with 
EIF2AK2 are unable to suppress autophagy. Both STAT3-targeting agents (i.e., 
Stattic, JSI-124 and WP1066) and EIF2AK2 activators (such as the double-strand 
RNA mimetic polyinosinic:polycytidylic acid) are capable of disrupting the 
inhibitory interaction between STAT3 and EIF2AK2 in cellula, yet only the latter 
does so in cell-free systems in vitro. A further screen designed to identify 
EIF2AK2-dependent autophagy inducers revealed that several fatty acids including 
palmitate trigger autophagy via a pathway that involves the disruption of the 
STAT3-EIF2AK2 complex as well as the phosphorylation of mitogen-activated 
protein kinase 8/c-Jun N-terminal kinase 1 (MAPK8/JNK1) and EIF2S1. These 
results reveal an unsuspected crosstalk between cellular metabolism (fatty 
acids), pro-inflammatory signaling (STAT3), innate immunity (EIF2AK2), and 
translational control (EIF2S1) that regulates autophagy.