Autophagy begins with the formation of autophagosomes, a process that depends on the activity of the serine/threonine kinase ULK1 (hATG1). Although earlier studies indicated that ULK1 activity is regulated by dynamic polyubiquitination, the deubiquitinase involved in the regulation of ULK1 remained unknown. In this study, we demonstrate that ubiquitin-specific protease 20 (USP20) acts as a positive regulator of autophagy initiation through stabilizing ULK1. At basal state, USP20 binds to and stabilizes ULK1 by removing the ubiquitin moiety, thereby interfering with the lysosomal degradation of ULK1. The stabilization of basal ULK1 protein levels is required for the initiation of starvation-induced autophagy, since the depletion of USP20 by RNA interference inhibits LC3 puncta formation, a marker of autophagic flux. At later stages of autophagy, USP20 dissociates from ULK1, resulting in enhanced ULK1 degradation and apoptosis. Taken together, our findings provide the first evidence that USP20 plays a crucial role in autophagy initiation by maintaining the basal expression level of ULK1.

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Receptors for advanced glycation end‐products (RAGE) is transmembrane receptor of the immunoglobulin superfamily with an extracellular domain that consists of a variable region as well as two constant regions. RAGE and its ligand interaction are often referred to result in pro‐inflamatory gene activation and effect in diabetic complications, Alzheimer's disease and even some tumors. V‐domain of RAGE is determinant for binding with Amyloid‐β (Aβ). RAGE‐mediated Aβ transport of circulating Aβ across blood brain barrier (BBB) is important in pathogenesis of cerebrovascular β‐amyloidosis. In this study, we show that two β‐strands of RAGE are required for interaction with Aβ. Serial deletion analysis and site‐directed mutagenesis of RAGE V domain show that the third and eighth β‐strands are important for interaction with Aβ. Wild‐type RAGE activates the NF‐κB signaling pathway in response to Aβ peptide treatment, while a RAGE mutant defective in Aβ binding does not. Furthermore, using peptide of third and eighth β‐strand of RAGE or monoclonal antibody targeting Aβ interaction interface of RAGE V domain, interaction of RAGE and Aβ is abolished and transportation of Aβ peptide across the blood brain barrier is blocked. These results provide information crucial to the development of RAGE‐derived therapeutic reagents for Alzheimer disease.