Proteasome Stress in Skeletal Muscle Mounts a Long-Range Protective Response that Delays Retinal and Brain Aging [Human]

The proteasome maintains protein quality during aging and disease. Challenges to proteasome function can be compensated by local proteasome stress responses. However, whereas proteasome stress is also sensed systemically is unknown. In Drosophila , we find that proteasome stress in skeletal muscle non-autonomously promotes the degradation of proteasome substrates in distant tissues during aging. Several muscle-secreted factors (myokines) are upregulated by proteasomal stress via C/EBP transcription factors, including the amylase Amyrel, which increases the circulating levels of the disaccharide maltose. Muscle-specific Amyrel overexpression promotes the degradation of proteasome substrates in the aging brain and retina via the transcriptional induction of chaperones and proteases. Conversely, RNAi for maltose transporters worsens proteostasis and reduces the expression of Amyrel-induced genes in the brain. Moreover, maltose preserves protein quality in cell culture and human cortical brain organoids challenged by thermal stress. Thus, proteasome stress in skeletal muscle mounts a systemic adaptive response via amylase/maltose signaling.