Decorin is an autophagy-inducible proteoglycan and is required for proper in vivo autophagy

We have recently discovered that soluble extracellular matrix constituents regulate autophagy via an outside-in signaling pathway. Decorin, a secreted proteoglycan, evokes autophagy in endothelial cells and mitophagy in breast carcinoma cells. However, it is not known whether decorin expression can be regulated by autophagic stimuli such as mTOR inhibition or nutrient deprivation. Thus, we tested whether pro-autophagic stimuli could affect decorin expression in mouse cardiac tissue and whether the absence of decorin could disrupt the in vivo autophagic response. We found that nutrient deprivation induced decorin at the mRNA and protein level in vivo and in vitro, a process regulated at the transcriptional level by inhibiting the canonical mTOR pathway. Moreover, Dcn-/- mice displayed an aberrant response to fasting compared to wild-type mice. Our study establishes a new role for an extracellular matrix proteoglycan and provides a mechanistic role for soluble decorin in regulating a fundamental intracellular catabolic process.