Autophagy hub-protein p62 orchestrates oxidative, endoplasmic reticulum stress, and inflammatory responses post-ischemia, exacerbating stroke outcome
Xingyun Quan, Yukun Yang, Xiaolong Liu, Britta Kaltwasser, Matthias Pillath‐Eilers, Bernd Walkenfort, Sylvia Voortmann, Ayan Mohamud Yusuf, Nina Hagemann, Chen Wang, Mike Hasenberg, Dirk M. Hermann, Ulf Brockmeier
Abstract
Autophagy has crucial roles for ischemia/reperfusion (I/R) injury. To define the role of the autophagy hub protein p62/SQSTM1 in I/R injury, we conducted gain-of-function and loss-of-function experiments in a set of cell types, including two neuron-like cell lines, primary neurons, brain endothelial and astroglial-like cells, which we combined with mouse ischemic stroke studies. p62 levels post-I/R increased alongside intracellular ROS changes. p62 overexpression increased and p62 knockdown or pharmacological deactivation reduced I/R injury. Autophagic flux was p62-dependent, but oxygen-independent. Using p62 domain deletion mutants we identified p62's ZZ domain as key factor mediating autophagy and cell death. Death-promoting effects of p62 involved elevated ROS burden. At the same time, p62 activated a broad network of cytoprotective responses, which included NRF2-associated antioxidant signaling and inhibition of the pro-inflammatory NFκB pathway, which were bidirectionally linked with p62, and downregulation of the ER stress sensor BiP/GRP78 with consecutive activation of the UPR PERK branch. Our study establishes p62 as a master regulator of I/R injury, which offers itself as target for stroke therapies.