Lysosomal damage triggers a p38 MAPK-dependent phosphorylation cascade to promote lysophagy via the small heat shock protein HSP27

ABSTRACT: Maintenance of lysosomal integrity is essential for cell viability. Upon injury, lysosomes may be targeted for degradation via a form of selective autophagy known as lysophagy, in which autophagosomes engulf damaged lysosomes following the recruitment of adaptor proteins. One of these adaptors, SQSTM1/p62, promotes lysophagy via liquid-like phase separation on damaged lysosomes. The formation of p62 condensates is regulated by the heat shock protein HSP27. Here, we demonstrate a direct interaction between HSP27 and p62. We used structural modeling to predict the binding interface between HSP27 and p62, and found several disease-associated mutations that map to this interface and disrupt the interaction. We then used proteomics to identify post-translational modifications of HSP27 that determine HSP27 recruitment to stressed lysosomes, finding robust phosphorylation at Serine residues 15, 78, and 82. We characterized the signaling mechanism leading to HSP27 phosphorylation. We find that p38 MAPK and its effector kinase MK2 are activated upon lysosomal damage by the kinase mTOR and the production of intracellular reactive oxygen species (ROS). Increased ROS activates p38 MAPK, which in turn allows MK2-dependent phosphorylation of HSP27. Either depletion of HSP27 or inhibition of HSP27 phosphorylation alters the liquidity of p62 condensates, significantly inhibiting p62-dependent lysophagy. Thus, we define a novel lysosomal quality control mechanism in which lysosomal injury triggers a p38 MAPK/MK2 signaling cascade regulating p62-dependent lysophagy. Further, this signaling cascade is activated by a variety of cellular stressors, including oxidative and heat stress, suggesting that other forms of selective autophagy may be regulated by p38 MAPK/MK2/HSP27.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Hossein Fazelinia  

LAB HEAD: Erika L. F. Holzbaur, Ph.D.

PROVIDER: PXD051927 | Pride | 2024-10-22

REPOSITORIES: Pride