Rapid and persistent loss of TXNIP in HT22 neuronal cells under carbonyl and hyperosmotic stress

Thioredoxin interacting protein (TXNIP) binds to thioredoxin thereby limiting its activity, but it also promotes internalization of glucose transporters, participates in inflammasome activation, and controls autophagy. Published data and this work demonstrate that TXNIP responds to a number of apparently unrelated stresses, such as serum deprivation, pH change, and oxidative, osmotic and carbonyl stress. Interestingly, we noticed that hyperosmotic (NaCl) and carbonyl (methylglyoxal, MGO) stresses in HT22 neuronal cells produced a rapid loss of TXNIP (half-life ∼12 min), prompting us to search for possible mechanisms controlling this TXNIP loss, including pH change, serum deprivation, calcium metabolism and inhibition of the proteasome and other proteases, autophagy and MAPKs. None of these routes stopped the TXNIP loss induced by hyperosmotic and carbonyl stress. Besides transcriptional, translational and microRNA regulation, there is evidence indicating that mTOR and AMPK also control TXNIP expression. Indeed, AMPK-deficient mouse embryonic fibroblasts failed to respond to phenformin (AMPK activator) and compound C (AMPK inhibitor), while rapamycin induced a marked increase in TXNIP levels, confirming the known AMPK/mTOR control over TXNIP. However, the TXNIP loss induced by NaCl or MGO were observed even in AMPK deficient MEFs or after mTOR inhibition, indicating AMPK/mTOR does not participate in this rapid TXNIP loss. These results suggest that rapid TXNIP loss is a general and immediate response to stress that can improve energy availability and antioxidant protection, eventually culminating in better cell survival.