Acetylation-dependent remodeling of the secretory pathway shapes the senescence-associated secretome

Cellular senescence is characterized by stable cell cycle arrest and the senescence-associated secretory phenotype (SASP), which drives tissue remodeling and inflammation. Underlying SASP with its increased secretion of cytokines and other secreted proteins is a massive reorganization of the secretory pathway. While transcriptional regulation of senescence has been extensively studied, the contribution of post-translational modifications (PTM) to secretory pathway regulation remains poorly understood. Here, we combined quantitative proteomics with multi-layered PTM profiling of phosphorylation, ubiquitination and acetylation to investigate how intracellular trafficking and secretion are regulated in senescence. Using doxorubicin-induced senescence as the primary model, we identified extensive proteome remodeling, with pronounced changes in ER-Golgi-associated pathways and secretory machinery. Acetylation emerged as the most prominently regulated PTM, particularly affecting proteins involved in vesicle trafficking and ER proteostasis. Comparable proteome and PTM remodeling were also observed in replicative senescence, indicating that these changes are not restricted to a single senescence model. Functional analyses revealed activation signatures of the acetyltransferases p300/CBP, linking global acetylation changes to enzymatic activity. Pharmacological inhibition of p300/CBP using A485 selectively modulated senescence-associated features without reversing growth arrest, consistent with a senomorphic-like effect during senescence establishment. Secretome profiling further demonstrated changes in the composition of secreted factors, consistent with modulation of the senescence-associated secretory phenotype. Together, these findings indicate that acetylation-dependent regulation of the secretory pathway shapes the senescence-associated secretome, revealing a mechanistic link between post-translational regulation, intracellular trafficking, and extracellular signaling in senescence.