THE KDEL RECEPTOR INDUCES AUTOPHAGY TO PROMOTE THE CLEARANCE OF NEURODEGENERATIVE DISEASE-RELATED PROTEINS

Endoplasmic reticulum (ER) stress is involved in neurodegenerative diseases, and the KDEL (Lys-Asp-Glu-Leu motif) receptor (KDELR) plays a key role in ER quality control and in the ER stress response. The subcellular distribution of KDELR is dynamic and related to its ligand binding status and its expression level. Here, we show that KDELR mRNA is upregulated upon thapsigargin treatment, which induces ER stress. Moreover, overexpressed KDELR partially redistributes to the lysosome and activates autophagy. The R169N mutant, a ligand binding-defective form of KDELR, and D193N, a transport-defective form of KDELR, both fail to trigger autophagy. Overexpression of KDELR activates extracellular signal-regulated kinases (ERKs). Both the activation of ERKs and autophagy induced by KDELR could be blocked by PD98059, an inhibitor of mitogen extracellular kinase 1 (MEK1). The overexpression of some neurodegenerative disease-related proteins, such as amyotrophic lateral sclerosis (ALS)-linked G93A superoxide dismutase 1 (SOD1), Parkinson's disease-associated A53T alpha-synuclein and Huntington's disease-related expanded huntingtin, increase the mRNA levels of KDELR. Moreover, the overexpressed KDELR promotes the clearance of these disease proteins through autophagy. Taken together, our data provide evidence that KDELR, as a novel inducer of autophagy, participates in the degradation of misfolded neurodegenerative disease-related proteins. (C) 2011 IBRO. Published by Elsevier Ltd. All rights reserved.