An artificial peptide inhibits autophagy through calcineurin-TFEB pathway

We previously reported that a bioactive peptide (pep3) can potently inhibit the enzyme activity of purified calcineurin (CN). In this paper, we further demonstrate that transfected pep3 can strongly inhibit CN enzyme activity in HEK293 cells. Transcription factor EB (TFEB) plays an important role in the autophagy-lysosome pathway (ALP) as one of the substrates of CN, so we study the effect of pep3 on the CN-TFEB-ALP pathway. Pep3 can significantly inhibit the mRNA levels of the TFEB downstream genes and the expression of the autophagy-associated proteins, and autophagy flux in HEK293 cells. We also validated the inhibitory effect of pep3 on autophagy in mice. These findings may provide a new idea for discovering more CN inhibitors and autophagy inhibitory drugs.